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1
Leitinger, Birgit y Nancy Hogg. "Effects of I Domain Deletion on the Function of the β2 Integrin Lymphocyte Function-associated Antigen-1". Molecular Biology of the Cell 11, n.º 2 (febrero de 2000): 677–90. http://dx.doi.org/10.1091/mbc.11.2.677.
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A subset of integrin α subunits contain an I domain, which is important for ligand binding. We have deleted the I domain from the β2 integrin lymphocyte function-asssociated antigen-1 (LFA-1) and expressed the resulting non–I domain-containing integrin (ΔI-LFA-1) in an LFA-1-deficient T cell line. ΔI-LFA-1 showed no recognition of LFA-1 ligands, confirming the essential role of the I domain in ligand binding. Except for I domain monoclonal antibodies (mAbs), ΔI-LFA-1 was recognized by a panel of anti-LFA-1 mAbs similarly to wild-type LFA-1. However, ΔI-LFA-1 had enhanced expression of seven mAb epitopes that are associated with β2 integrin activation, suggesting that it exhibited an “active” conformation. In keeping with this characteristic, ΔI-LFA-1 induced constitutive activation of α4β1 and α5β1, suggesting intracellular signaling to these integrins. This “cross-talk” was not due to an effect on β1 integrin affinity. However, the enhanced activity was susceptible to inhibition by cytochalasin D, indicating a role for the cytoskeleton, and also correlated with clustering of β1 integrins. Thus, removal of the I domain from LFA-1 created an integrin with the hallmarks of a constitutively active receptor mediating signals into the cell. These findings suggest a key role for the I domain in controlling integrin activity.
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Lub, M., S. J. van Vliet, S. P. Oomen, R. A. Pieters, M. Robinson, C. G. Figdor y Y. van Kooyk. "Cytoplasmic tails of beta 1, beta 2, and beta 7 integrins differentially regulate LFA-1 function in K562 cells." Molecular Biology of the Cell 8, n.º 4 (abril de 1997): 719–28. http://dx.doi.org/10.1091/mbc.8.4.719.
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The beta 2 integrin lymphocyte function-associated antigen 1 (LFA-1) mediates activation-dependent adhesion of lymphocytes. To investigate whether lymphocyte-specific elements are essential for LFA-1 function, we expressed LFA-1 in the erythroleukemic cell line K562, which expresses only the integrin very late antigen 5. We observed that LFA-1-expressing K562 cannot bind to intercellular adhesion molecule 1-coated surfaces when stimulated by phorbol 12-myristate 13-acetate (PMA), whereas the LFA-1-activating antibody KIM185 markedly enhanced adhesion. Because the endogenously expressed beta 1 integrin very late antigen 5 is readily activated by PMA, we investigated the role of the cytoplasmic domain of distinct beta subunits in regulating LFA-1 function. Transfection of chimeric LFA-1 receptors in K562 cells reveals that replacement of the beta 2 cytoplasmic tail with the beta 1 but not the beta 7 cytoplasmic tail completely restores PMA responsiveness of LFA-1, whereas a beta 2 cytoplasmic deletion mutant of LFA-1 is constitutively active. Both deletion of the beta 2 cytoplasmic tail or replacement by the beta 1 cytoplasmic tail alters the localization of LFA-1 into clusters, thereby regulating LFA-1 activation and LFA-1-mediated adhesion to intercellular adhesion molecule 1. These data demonstrate that distinct signaling routes activate beta 1 and beta 2 integrins through the beta-chain and hint at the involvement of lymphocyte-specific signal transduction elements in beta 2 and beta 7 integrin activation that are absent in the nonlymphocytic cell line K562.
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Dransfield, I., C. Cabañas, A. Craig y N. Hogg. "Divalent cation regulation of the function of the leukocyte integrin LFA-1." Journal of Cell Biology 116, n.º 1 (1 de enero de 1992): 219–26. http://dx.doi.org/10.1083/jcb.116.1.219.
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The integrin lymphocyte function-associated antigen-1 (LFA-1) expressed on T cells serves as a useful model for analysis of leukocyte integrin functional activity. We have assessed the role of divalent cations Mg2+, Ca2+, and Mn2+ in LFA-1 binding to ligand intercellular adhesion molecule-1 (ICAM-1) and induction of the divalent cation-dependent epitope recognized by mAb 24. Manganese strongly promoted both expression of the 24 epitope and T cell binding to ICAM-1 via LFA-1, suggesting that Mn2+ is able to directly alter the conformation of LFA-1 in a manner that favors ligand binding. Since Mn2+ also promotes functional activity of other integrins, parallels in mechanism of ligand binding may span the integrin family. In contrast, induction of 24 epitope expression by Mg2+ required removal of Ca2+ from T cell LFA-1 with EGTA. Furthermore, binding of mAb 24 to T cell LFA-1 in the presence of either Mn2+ or Mg2+ was found to be specifically inhibited by Ca2+, suggestive of a negative regulatory role for Ca2+ in the control of leukocyte integrin function. Analysis of T cell binding to ICAM-1 via LFA-1 in the presence of Mg2+ or Mn2+, confirmed that Ca2+ exerted inhibitory effects upon LFA-1 function. The implication of our findings is that Ca2+ bound with relatively high affinity to LFA-1 may serve to maintain an inactive state. Thus induction of function and 24 epitope expression may occur as a result of displacement of Ca2+ from leukocyte integrins or alternatively, such activators may be able to impose the required conformational change in the presence of bound Ca2+.
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Leitinger, Birgit y Nancy Hogg. "The involvement of lipid rafts in the regulation of integrin function". Journal of Cell Science 115, n.º 5 (1 de marzo de 2002): 963–72. http://dx.doi.org/10.1242/jcs.115.5.963.
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Integrin activity on cells such as T lymphocytes is tightly controlled. Here we demonstrate a key role for lipid rafts in regulating integrin function. Without stimulation integrin LFA-1 is excluded from lipid rafts, but following activation LFA-1 is mobilised to the lipid raft compartment. An LFA-1 construct from which the I domain has been deleted mimics activated integrin and is constitutively found in lipid rafts. This correlation between integrin activation and raft localisation extends to a second integrin,α4β1, and the clustering of α4β1 is also raft dependent. Both LFA-1 and α4β1-mediated adhesion is dependent upon intact lipid rafts providing proof of the functional relevance of the lipid raft localisation. Finally we find that non-raft integrins are excluded from the rafts by cytoskeletal constraints. The presence of integrin in lipid rafts under stimulating conditions that activate these receptors strongly indicates that the rafts have a key role in positively regulating integrin activity.
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Geijtenbeek, Teunis B. H., Yvette van Kooyk, Sandra J. van Vliet, Maurits H. Renes, Reinier A. P. Raymakers y Carl G. Figdor. "High Frequency of Adhesion Defects in B-Lineage Acute Lymphoblastic Leukemia". Blood 94, n.º 2 (15 de julio de 1999): 754–64. http://dx.doi.org/10.1182/blood.v94.2.754.
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Abstract Aberrant proliferation, differentiation, and/or migration of progenitors observed in various hematological malignancies may be caused by defects in expression and/or function of integrins. In this study, we have developed a new fluorescent beads adhesion assay that facilitates flow cytometric investigation of lymphocyte function-associated antigen 1 (LFA-1)– and very late activation antigen-4 (VLA-4)–mediated functional adhesion in B-lineage acute lymphoblastic leukemia (ALL) of both the CD10− and CD10+ (leukemic) cell population within one blood or bone marrow sample. Surprisingly, of the 20 B-lineage ALL patients investigated, 17 contained a leukemic cell population with LFA-1– and/or VLA-4–mediated adhesion defects. Five patients contained CD10+ cells that did not exhibit any LFA-1–mediated adhesion due to the lack of LFA-1 surface expression. The CD10+ cells from 10 ALL patients expressed LFA-1 that could not be activated by the phorbol ester phorbol 12-myristate 13-acetate (PMA), whereas the CD10− cells expressed a functional LFA-1. Seven patients contained CD10+ cells that expressed a PMA-unresponsive form of VLA-4. The PMA unresponsiveness of the integrins LFA-1 and VLA-4 expressed by the CD10+ cells may be due to mutations in the integrins itself, in protein kinases, or in other intracellular molecules involved in integrin adhesion. These data clearly demonstrate the importance of investigating integrin function in addition to integrin surface expression. The strikingly high frequency (85%) of adhesion defects in ALL could suggest a causal relationship between integrin-mediated adhesion and B-lineage ALL.
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Geijtenbeek, Teunis B. H., Yvette van Kooyk, Sandra J. van Vliet, Maurits H. Renes, Reinier A. P. Raymakers y Carl G. Figdor. "High Frequency of Adhesion Defects in B-Lineage Acute Lymphoblastic Leukemia". Blood 94, n.º 2 (15 de julio de 1999): 754–64. http://dx.doi.org/10.1182/blood.v94.2.754.414k11_754_764.
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Aberrant proliferation, differentiation, and/or migration of progenitors observed in various hematological malignancies may be caused by defects in expression and/or function of integrins. In this study, we have developed a new fluorescent beads adhesion assay that facilitates flow cytometric investigation of lymphocyte function-associated antigen 1 (LFA-1)– and very late activation antigen-4 (VLA-4)–mediated functional adhesion in B-lineage acute lymphoblastic leukemia (ALL) of both the CD10− and CD10+ (leukemic) cell population within one blood or bone marrow sample. Surprisingly, of the 20 B-lineage ALL patients investigated, 17 contained a leukemic cell population with LFA-1– and/or VLA-4–mediated adhesion defects. Five patients contained CD10+ cells that did not exhibit any LFA-1–mediated adhesion due to the lack of LFA-1 surface expression. The CD10+ cells from 10 ALL patients expressed LFA-1 that could not be activated by the phorbol ester phorbol 12-myristate 13-acetate (PMA), whereas the CD10− cells expressed a functional LFA-1. Seven patients contained CD10+ cells that expressed a PMA-unresponsive form of VLA-4. The PMA unresponsiveness of the integrins LFA-1 and VLA-4 expressed by the CD10+ cells may be due to mutations in the integrins itself, in protein kinases, or in other intracellular molecules involved in integrin adhesion. These data clearly demonstrate the importance of investigating integrin function in addition to integrin surface expression. The strikingly high frequency (85%) of adhesion defects in ALL could suggest a causal relationship between integrin-mediated adhesion and B-lineage ALL.
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Luo, Xuan, Valentine Seveau de Noray, Laurene Aoun, Martine Biarnes-Pelicot, Pierre-Olivier Strale, Vincent Studer, Marie-Pierre Valignat y Olivier Theodoly. "Lymphocytes perform reverse adhesive haptotaxis mediated by LFA-1 integrins". Journal of Cell Science 133, n.º 16 (21 de julio de 2020): jcs242883. http://dx.doi.org/10.1242/jcs.242883.
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ABSTRACTCell guidance by anchored molecules, or haptotaxis, is crucial in development, immunology and cancer. Adhesive haptotaxis, or guidance by adhesion molecules, is well established for mesenchymal cells such as fibroblasts, whereas its existence remains unreported for amoeboid cells that require less or no adhesion in order to migrate. We show that, in vitro, amoeboid human T lymphocytes develop adhesive haptotaxis mediated by densities of integrin ligands expressed by high endothelial venules. Moreover, lymphocytes orient towards increasing adhesion with VLA-4 integrins (also known as integrin α4β1), like all mesenchymal cells, but towards decreasing adhesion with LFA-1 integrins (also known as integrin αLβ4), which has not previously been observed. This counterintuitive ‘reverse haptotaxis’ cannot be explained by existing mechanisms of mesenchymal haptotaxis involving either competitive anchoring of cell edges under tension or differential integrin-activated growth of lamellipodia, because they both favor orientation towards increasing adhesion. The mechanisms and functions of amoeboid adhesive haptotaxis remain unclear; however, multidirectional integrin-mediated haptotaxis might operate around transmigration ports on endothelia, stromal cells in lymph nodes, and inflamed tissue where integrin ligands are spatially modulated.
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Porter, Joanna C. y Nancy Hogg. "Integrin Cross Talk: Activation of Lymphocyte Function-associated Antigen-1 on Human T Cells Alters α4β1- and α5β1-mediated Function". Journal of Cell Biology 138, n.º 6 (22 de septiembre de 1997): 1437–47. http://dx.doi.org/10.1083/jcb.138.6.1437.
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A regulated order of adhesion events directs leukocytes from the vascular compartment into injured tissues in response to inflammatory stimuli. We show that on human T cells, the interaction of the β2 integrin leucocyte function–associated antigen-1 (LFA-1) with its ligand intercellular adhesion molecule-1 (ICAM-1) will decrease adhesion mediated by α4β1 and, to a lesser extent, α5β1. Similar inhibition is also seen when T cells are exposed to mAb 24, which stabilizes LFA-1 in an active state after triggering integrin function through divalent cation Mg2+, PdBu, or T cell receptor/ CD3 complex (TCR/CD3) cross-linking. Such cross talk decreases α4β1 integrin–mediated binding of T cells to fibronectin and vascular cell adhesion molecule-1 (VCAM-1). In contrast, ligand occupancy or prolonged activation of β1 integrin has no effect on LFA-1 adhesion to ICAM-1. We also show that T cell migration across fibronectin, unlike adhesion, is mediated solely by α5β1, and is increased when the α4β1-mediated component of fibronectin adhesion is decreased either by cross talk or the use of α4-blocking mAb. The ability of mAb 24 Fab′ fragments to induce cross talk without cross-linking LFA-1 suggests signal transduction through the active integrin. These data provide the first direct evidence for cross talk between LFA-1 and β1 integrins on T cells. Together, these findings imply that activation of LFA-1 on the extravasating T cell will decrease the binding to VCAM-1 while enhancing the subsequent migration on fibronectin. This sequence of events provides a further level of complexity to the coordination of T cell integrins, whose sequential but overlapping roles are essential for transmigration.
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Smith, Andrew, Yolanda R. Carrasco, Paula Stanley, Nelly Kieffer, Facundo D. Batista y Nancy Hogg. "A talin-dependent LFA-1 focal zone is formed by rapidly migrating T lymphocytes". Journal of Cell Biology 170, n.º 1 (27 de junio de 2005): 141–51. http://dx.doi.org/10.1083/jcb.200412032.
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Cells such as fibroblasts and endothelial cells migrate through the coordinated responses of discrete integrin-containing focal adhesions and complexes. In contrast, little is known about the organization of integrins on the highly motile T lymphocyte. We have investigated the distribution, activity, and cytoskeletal linkage of the integrin lymphocyte function associated antigen-1 (LFA-1) on human T lymphocytes migrating on endothelial cells and on ligand intercellular adhesion molecule-1 (ICAM-1). The pattern of total LFA-1 varies from low expression in the lamellipodia to high expression in the uropod. However, high affinity, clustered LFA-1 is restricted to a mid-cell zone that remains stable over time and over a range of ICAM-1 densities. Talin is essential for the stability and formation of the LFA-1 zone. Disruption of the talin–integrin link leads to loss of zone integrity and a substantial decrease in speed of migration on ICAM-1. This adhesive structure, which differs from the previously described integrin-containing attachments displayed by many other cell types, we have termed the “focal zone.”
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Petruzzelli, L., L. Maduzia y T. A. Springer. "Activation of lymphocyte function-associated molecule-1 (CD11a/CD18) and Mac-1 (CD11b/CD18) mimicked by an antibody directed against CD18." Journal of Immunology 155, n.º 2 (15 de julio de 1995): 854–66. http://dx.doi.org/10.4049/jimmunol.155.2.854.
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Abstract The beta 2-integrin (CD18) family members bind to their ligands subsequent to activation of a number of well defined and diverse signal transduction pathways. The precise molecular changes associated with activation of the integrin family members have remained elusive. Here, we characterize a monoclonal, CBR LFA-1/2, that binds to the beta 2-subunit and is able to mimic activation induced upon stimulation by phorbol esters. The Ab induces binding of the LFA-1-expressing cell line, JY, to ICAM-1 (CD54) and ICAM-3 (CD50). Activation of binding by this Ab is independent of Fc interactions and does not occur through cross-linking at the cell surface, because the Fab fragment of the Ab is able to modulate the same effect. Stimulation of neutrophils with CBR LFA-1/2 induces binding to ICAM-1 through activation of both LFA-1 and Mac-1. Activation of Mac-1 by CBR LFA-1/2 was further confirmed by stimulation of neutrophil binding to fibrinogen, a ligand for Mac-1. CBR LFA-1/2 lowers by 10-fold the concentration of Mg2+ required to achieve maximal binding of LFA-1 to ICAM-1. It therefore appears that CBR LFA-1/2 induces a conformational change that directly increases the avidity of beta 2-integrins for ligands.
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Evans, Betsy J., Alison McDowall, Peter C. Taylor, Nancy Hogg, Dorian O. Haskard y R. Clive Landis. "Shedding of lymphocyte function–associated antigen-1 (LFA-1) in a human inflammatory response". Blood 107, n.º 9 (1 de mayo de 2006): 3593–99. http://dx.doi.org/10.1182/blood-2005-09-3695.
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Shedding of adhesion molecules has been described for members of the selectin and immunoglobulin superfamilies, but integrins are not known to be shed. Here, we describe shedding of the integrin lymphocyte function–associated antigen-1 (LFA-1; CD11a/CD18) from human leukocytes during the cutaneous inflammatory response to the blistering agent cantharidin. Expression of LFA-1 was significantly diminished on blister-infiltrated neutrophils (P < .001) and monocytes (P = .02) compared with cells in peripheral blood, but expression on lymphocytes remained unchanged. A capture enzyme-linked immunosorbent assay (ELISA) indicated that LFA-1 was shed into blister fluid as a heterodimer expressing an intact headpiece with I and I-like epitopes. However, a CD11a central region epitope, G25.2, was absent and this remained expressed as a “stub” on the cell surface of blister neutrophils. Western analysis of soluble LFA-1 revealed a truncated 110-kDa CD11a chain and a minimally truncated 86-kDa CD18 chain. However, LFA-1 was shed in a ligand-binding conformation, since it expressed KIM-127 and 24 activation epitopes and bound to solid-phase ICAM-1. Shed LFA-1 was also detected in a synovial effusion by ELISA and Western analysis. We hypothesize that LFA-1 shedding may play a role in leukocyte detachment after transendothelial migration and in regulating integrin-dependent outside-in signaling.
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Chen, Ying-Yu, Mobeen Malik, Brian E. Tomkowicz, Ronald G. Collman y Andrzej Ptasznik. "BCR-ABL1 Disrupts SDF-1-Dependent Hematopoietic Cell Migration and Adhesion through the LFA-1 Integrin-Mediated Mechanism." Blood 110, n.º 11 (16 de noviembre de 2007): 1011. http://dx.doi.org/10.1182/blood.v110.11.1011.1011.
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Abstract Stromal-derived factor-1 (SDF-1) and its receptor, CXCR4, are essential for normal stem/progenitor cell movement, adherence, and retention within the bone marrow environment. Two mechanisms through which BCR-ABL1 are thought to disrupt CXCR4-mediated chemotactic responses have been described in leukemia: the inhibition of CXCR4 expression (Geay et al. 2005, Cancer Res.) and intra-cellular signaling defects without modification of CXCR4 expression (Salgia et al. 1999, Blood; Ptasznik et al. 2002, J. Exp. Med.). These opposing mechanisms suggest that the actual situation is more complex and that new signaling paradigms are needed. To address this, we studied the effects of BCR-ABL1 on SDF-1-dependent, integrin-mediated, migration and adhesion of hematopoietic precursors. Stimulation of BCR-ABL1(−) hematopoietic cells with SDF-1 showed reduced cell adherence to surfaces coated with ICAM-1 (a ligand for the LFA-1 integrin), which was associated with down-regulated expression of activation-dependent epitopes of the β2 integrin, LFA-1, on hematopoietic cells. Inhibition of Lyn expression with siRNA prevented the SDF-1-triggered down-regulation of LFA-1 and cell adherence, indicating that CXCR4 inhibited the function of LFA-1 through Lyn. Expression of BCR-ABL1 in these cells resulted in increased expression of activation-dependent epitopes of LFA-1 and prevented SDF-1-dependent regulatory effects on both LFA-1 affinity and ICAM-1 adherence. Also, expression of BCR-ABL1 prevented Lyn-mediated regulation of cell adhesion to ICAM-1 as well as Lyn-mediated regulation of LFA-1 affinity. These results indicate that BCR-ABL1 constitutively increases the affinity of the LFA-1 integrin to its ligand ICAM-1, locking the integrin into an “active” conformation. The net result is the loss of responsiveness of LFA-1 to SDF-1-induced ‘inside-out’ signaling involving CXCR4 and Lyn kinase. Because in our experiments BCR-ABL1 had no significant effect on the expression of CXCR4 in Mo7e cells, transfected with low and high amounts of p210-BCR-ABL, or in primary BCR-ABL(+) cells from CML blast crisis patients (n=3), we conclude that BCR-ABL1 inhibits CXCR4-triggered ‘inside-out’ integrin signaling rather than CXCR4 expression. Taken together, we propose that BCR-ABL1 disrupts the signaling link between the chemokine receptor, CXCR4 and the β2 integrin LFA-1 so as to inhibit normal SDF-1-mediated chemotaxis and adhesion in hematopoietic cells.
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Henderson, Robert B., Lina H. K. Lim, Philippe A. Tessier, Felicity N. E. Gavins, Meg Mathies, Mauro Perretti y Nancy Hogg. "The Use of Lymphocyte Function–Associated Antigen (Lfa)-1–Deficient Mice to Determine the Role of Lfa-1, Mac-1, and α4 Integrin in the Inflammatory Response of Neutrophils". Journal of Experimental Medicine 194, n.º 2 (16 de julio de 2001): 219–26. http://dx.doi.org/10.1084/jem.194.2.219.
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After injury or infection, neutrophils rapidly migrate from the circulation into tissues by means of an orderly progression of adhesion receptor engagements. Neutrophils have been previously considered to use selectins exclusively to roll on vessels before an adhesion step mediated by the β2 integrins, lymphocyte function–associated antigen (LFA)-1, and Mac-1. Here we use LFA-1−/− mice, function blocking monoclonal antibodies, and intravital microscopy to investigate the roles of LFA-1, Mac-1, and α4 integrins in neutrophil recruitment in vivo. For the first time, we show that LFA-1 makes a contribution to neutrophil rolling by stabilizing the transient attachment or tethering phase of rolling. In contrast, Mac-1 does not appear to be important for either rolling or firm adhesion, but instead contributes to emigration from the vessel. Blocking Mac-1 in the presence of LFA-1 significantly reduces emigration, suggesting cooperation between these two integrins. Low levels of α4β1 integrin can be detected on neutrophils from LFA-1+/+ and −/− mice. These cells make use of α4β1 during the rolling phase, particularly in the absence of LFA-1. Thus LFA-1 and α4β1, together with the selectins, are involved in the rolling phase of neutrophil recruitment, and, in turn, affect the later stages of the transmigration event.
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Yuki, Koichi, Nathan S. Astrof, Clay Bracken, Sulpicio G. Soriano y Motomu Shimaoka. "Sevoflurane Binds and Allosterically Blocks Integrin Lymphocyte Function-associated Antigen-1". Anesthesiology 113, n.º 3 (1 de septiembre de 2010): 600–609. http://dx.doi.org/10.1097/aln.0b013e3181e89a77.
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Background Volatile anesthetics have been shown to modify immune cell functions via several mechanisms, some of which have been only partially elucidated. We demonstrated that isoflurane inhibits primary leukocyte integrin lymphocyte function-associated antigen-1 (LFA-1) by binding to the allosteric cavity critical for conformational activation to its high-affinity form. It remains to be determined whether the allosteric inhibition of LFA-1 by isoflurane can be generalized to other anesthetics such as sevoflurane. Methods The effects of sevoflurane on the ability of LFA-1 to bind to its counter-ligand, intercellular adhesion molecule-1, was studied in leukocytes by flow cytometry. To examine whether sevoflurane acts directly on LFA-1, we measured ligand-binding using beads coated with purified LFA-1 protein. To distinguish between competitive versus allosteric inhibition, we analyzed the effects of sevoflurane on both wild-type and mutant-locked high-affinity LFA-1. One-way analysis of variance was employed for statistical analysis of the data. Nuclear magnetic resonance spectroscopy was used to identify sevoflurane binding site(s). Results Sevoflurane at clinically relevant concentrations inhibited the ligand-binding function of LFA-1 in leukocytes as well as in cell-free assays (P<0.05). Sevoflurane blocked wild-type but not locked high-affinity LFA-1, thereby demonstrating an allosteric mode of inhibition. Nuclear magnetic resonance spectroscopy revealed that sevoflurane bound to the allosteric cavity, to which LFA-1 allosteric antagonists and isoflurane also bind. Conclusions This study suggests that sevoflurane also blocks the activation-dependent conformational changes of LFA-1 to the high-affinity form. The allosteric mode of action exemplified by sevoflurane and isoflurane via LFA-1 might represent one of the underlying mechanisms of anesthetic-mediated immunomodulation.
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Semmrich, Monika, Andrew Smith, Carolin Feterowski, Sandra Beer, Britta Engelhardt, Dirk H. Busch, Bernadett Bartsch et al. "Importance of integrin LFA-1 deactivation for the generation of immune responses". Journal of Experimental Medicine 201, n.º 12 (13 de junio de 2005): 1987–98. http://dx.doi.org/10.1084/jem.20041850.
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The dynamic regulation of ligand binding is considered crucial for integrin function. However, the importance of activity regulation for integrin function in vivo is largely unknown. Here, we have applied gene targeting to delete the GFFKR sequence of the lymphocyte function-associated antigen–1 (LFA-1) αL subunit cytoplasmic domain in mouse germline. Lymphocytes from Lfa-1d/d mutant mice showed constitutive activation of LFA-1–mediated cell adhesion and impaired de-adhesion from intercellular adhesion molecule-1 that resulted in defective cell migration. In contrast, signaling through LFA-1 was not affected in Lfa-1d/d cells. T cell activation by superantigen-loaded and allogeneic APCs, cytotoxic T cell activity, T-dependent humoral immune responses, and neutrophil recruitment during aseptic peritonitis were impaired in Lfa-1d/d mice. Thus, deactivation of LFA-1 and disassembly of LFA-1–mediated cell contacts seem to be vital for the generation of normal immune responses.
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Lo, Charles G., Theresa T. Lu y Jason G. Cyster. "Integrin-dependence of Lymphocyte Entry into the Splenic White Pulp". Journal of Experimental Medicine 197, n.º 3 (3 de febrero de 2003): 353–61. http://dx.doi.org/10.1084/jem.20021569.
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The steps involved in lymphocyte homing to the white pulp cords of the spleen are poorly understood. We demonstrate here that the integrins lymphocyte function associated (LFA)-1 and α4β1 make essential and mostly overlapping contributions necessary for B cell migration into white pulp cords. T cell entry to the white pulp is also reduced by blockade of LFA-1 and α4β1. The LFA-1 ligand, intercellular adhesion molecule 1 is critical for lymphocyte entry and both hematopoietic cells and radiation-resistant cells contribute to this requirement. Vascular cell adhesion molecule 1 contributes to the α4β1 ligand requirement and a second ligand, possibly fibronectin, also plays a role. By contrast with the entry requirements, antigen-induced movement of B cells from follicles to the outer T zone is not prevented by integrin blocking antibodies. Comparison of the distribution of integrin-blocked B cells and B cells treated with the Gαi inhibitor, pertussis toxin, early after transfer reveals in both cases reduced accumulation in the inner marginal zone. These observations suggest that chemokine receptor signaling and the integrins LFA-1 and α4β1 function together to promote lymphocyte transit from the marginal zone into white pulp cords.
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Cambi, Alessandra, Ben Joosten, Marjolein Koopman, Frank de Lange, Inge Beeren, Ruurd Torensma, Jack A. Fransen, Maria Garcia-Parajó, Frank N. van Leeuwen y Carl G. Figdor. "Organization of the Integrin LFA-1 in Nanoclusters Regulates Its Activity". Molecular Biology of the Cell 17, n.º 10 (octubre de 2006): 4270–81. http://dx.doi.org/10.1091/mbc.e05-12-1098.
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The β2-integrin LFA-1 facilitates extravasation of monocytes (MOs) into the underlying tissues, where MOs can differentiate into dendritic cells (DCs). Although DCs express LFA-1, unlike MOs, they cannot bind to ICAM-1. We hypothesized that an altered integrin organization on the DC plasma membrane might cause this effect and investigated the relationship between membrane organization and function of LFA-1 on MOs and DCs. High-resolution mapping of LFA-1 surface distribution revealed that on MOs LFA-1 function is associated with a distribution in well-defined nanoclusters (100–150-nm diameter). Interestingly, a fraction of these nanoclusters contains primed LFA-1 molecules expressing the specific activation-dependent L16-epitope. Live imaging of MO–T-cell conjugates showed that only these primed nanoclusters are dynamically recruited to the cellular interface forming micrometer-sized assemblies engaged in ligand binding and linked to talin. We conclude that besides affinity regulation, LFA-1 function is controlled by at least three different avidity patterns: random distributed inactive molecules, well-defined ligand-independent proactive nanoclusters, and ligand-triggered micrometer-sized macroclusters.
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Hartmann, Tanja Nicole, Valentin Grabovsky, Wei Wang, Petra Desch, Stefan Wollner, Inbal Binsky, Alexandra Vallon-Eberhard et al. "Circulating B-cell chronic lymphocytic leukemia cells display impaired migration to lymph nodes due to reduced LFA-1 expression". Blood 112, n.º 11 (16 de noviembre de 2008): 3135. http://dx.doi.org/10.1182/blood.v112.11.3135.3135.
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Abstract Homing to secondary lymphoid organs and re-entry to bone marrow (BM) are central aspects of leukemic pathophysiology. We investigated the roles of the two major lymphocyte integrins LFA-1 and VLA-4 on B-cell chronic lymphocytic leukaemia (CLL) cells in these processes. We found that CLL cells expressed significantly reduced LFA-1 due to low beta2 integrin transcripts and displayed diminished adhesiveness to ICAM-1-expressing endothelium in vitro. VLA-4 expression was heterogenous but underwent rapid activation by the BM chemokine CXCL12. Nevertheless, CLL cells failed to transmigrate across VCAM-1, ICAM-1 and CXCL12 expressing endothelium due to their deficient LFA-1 expression. Furthermore, when injected into tail veins of immunodeficient mice, normal B cells rapidly homed to lymph nodes (LNs) in a LFA-1 dependent manner whereas CLL cells did not. CLL alike normal B lymphocytes used VLA-4 rather than LFA-1 to reenter the BM. In contrast, both normal and CLL B cells homed to mice spleen in an LFA-1- and VLA-4-independent manner. Our results suggest that CLL cells are deficient in LFA-1-dependent trafficking to LNs but residual subsets can still re-enter the BM. Integrin blocking could be therefore an efficient strategy to prevent circulating CLL cells from reaching prosurvival niches in LNs and BM and directing these cells to the spleen.
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Lefort, Craig T., Jan Rossaint, Markus Moser, Brian G. Petrich, Alexander Zarbock, Susan J. Monkley, David R. Critchley, Mark H. Ginsberg, Reinhard Fässler y Klaus Ley. "Distinct roles for talin-1 and kindlin-3 in LFA-1 extension and affinity regulation". Blood 119, n.º 18 (3 de mayo de 2012): 4275–82. http://dx.doi.org/10.1182/blood-2011-08-373118.
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Abstract In inflammation, neutrophils and other leukocytes roll along the microvascular endothelium before arresting and transmigrating into inflamed tissues. Arrest requires conformational activation of the integrin lymphocyte function-associated antigen-1 (LFA-1). Mutations of the FERMT3 gene encoding kindlin-3 underlie the human immune deficiency known as leukocyte adhesion deficiency-III. Both kindlin-3 and talin-1, another FERM domain-containing cytoskeletal protein, are required for integrin activation, but their individual roles in the induction of specific integrin conformers are unclear. Here, we induce differential LFA-1 activation in neutrophils through engagement of the selectin ligand P-selectin glycoprotein ligand-1 or the chemokine receptor CXCR2. We find that talin-1 is required for inducing LFA-1 extension, which corresponds to intermediate affinity and induces neutrophil slow rolling, whereas both talin-1 and kindlin-3 are required for induction of the high-affinity conformation of LFA-1 with an open headpiece, which results in neutrophil arrest. In vivo, both slow rolling and arrest are defective in talin-1–deficient neutrophils, whereas only arrest is defective in kindlin-3–deficient neutrophils. We conclude that talin-1 and kindlin-3 serve distinct functions in LFA-1 activation.
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Pruijt, Johannes F. M., Yvette van Kooyk, Carl G. Figdor, Ivan J. D. Lindley, Roel Willemze y Willem E. Fibbe. "Anti–LFA-1 Blocking Antibodies Prevent Mobilization of Hematopoietic Progenitor Cells Induced by Interleukin-8". Blood 91, n.º 11 (1 de junio de 1998): 4099–105. http://dx.doi.org/10.1182/blood.v91.11.4099.
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Abstract Previously, we have shown that interleukin (IL)-8 induces the rapid (15 to 30 minutes) mobilization of hematopoietic progenitor cells (HPC) in mice. Because integrins are essential for adhesion and transendothelial migration of HPC, we studied the involvement of the β2-integrin leukocyte function-associated antigen-1 (LFA-1) in IL-8–induced mobilization. After a single injection of blocking anti–LFA-1 antibodies, no mobilization of colony-forming cells was observed. In addition, when mice were pretreated with anti–LFA-1 or saline and subsequently injected with 30 μg of IL-8, mobilization of HPC was completely blocked. We showed that this was not due to anti–LFA-1 antibodies affecting colony formation, as addition of anti–LFA-1 antibodies to colony cultures in semisolid medium had no inhibitory activity. Also, anti-intercellular adhesion molecule (ICAM)-1 antibodies, directed to the main ligand of LFA-1 significantly inhibited the IL-8–induced mobilization. Furthermore, IL-1–induced mobilization was significantly inhibited by anti–LFA-1 antibodies. Because LFA-1 is reported to be expressed on more differentiated HPC, it was considered that the IL-8–induced mobilization of more primitive HPC would not be blocked by anti–LFA-1 antibodies. Transplantation of blood-derived mononuclear cells (MNC) from IL-8–mobilized animals pretreated with anti–LFA-1 antibodies protected only 25% of lethally irradiated recipient mice, whereas the radioprotection rate of control mice transplanted with MNC derived from IL-8-mobilized animals was 86% (P < .01). Anti-LFA–1 antibodies did not interfere with stem cell homing, as transplantation of IL-8-mobilized blood MNC, incubated in vitro with these antibodies resulted in 100% radioprotection. We conclude that anti–LFA-1 antibodies completely prevent the rapid mobilization of colony-forming cells and of cells with radioprotective capacity induced by IL-8. These results indicate a major role for the β2-integrin LFA-1 in the IL-8–induced mobilization of hematopoietic stem cells.
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Pruijt, Johannes F. M., Yvette van Kooyk, Carl G. Figdor, Ivan J. D. Lindley, Roel Willemze y Willem E. Fibbe. "Anti–LFA-1 Blocking Antibodies Prevent Mobilization of Hematopoietic Progenitor Cells Induced by Interleukin-8". Blood 91, n.º 11 (1 de junio de 1998): 4099–105. http://dx.doi.org/10.1182/blood.v91.11.4099.411k28_4099_4105.
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Previously, we have shown that interleukin (IL)-8 induces the rapid (15 to 30 minutes) mobilization of hematopoietic progenitor cells (HPC) in mice. Because integrins are essential for adhesion and transendothelial migration of HPC, we studied the involvement of the β2-integrin leukocyte function-associated antigen-1 (LFA-1) in IL-8–induced mobilization. After a single injection of blocking anti–LFA-1 antibodies, no mobilization of colony-forming cells was observed. In addition, when mice were pretreated with anti–LFA-1 or saline and subsequently injected with 30 μg of IL-8, mobilization of HPC was completely blocked. We showed that this was not due to anti–LFA-1 antibodies affecting colony formation, as addition of anti–LFA-1 antibodies to colony cultures in semisolid medium had no inhibitory activity. Also, anti-intercellular adhesion molecule (ICAM)-1 antibodies, directed to the main ligand of LFA-1 significantly inhibited the IL-8–induced mobilization. Furthermore, IL-1–induced mobilization was significantly inhibited by anti–LFA-1 antibodies. Because LFA-1 is reported to be expressed on more differentiated HPC, it was considered that the IL-8–induced mobilization of more primitive HPC would not be blocked by anti–LFA-1 antibodies. Transplantation of blood-derived mononuclear cells (MNC) from IL-8–mobilized animals pretreated with anti–LFA-1 antibodies protected only 25% of lethally irradiated recipient mice, whereas the radioprotection rate of control mice transplanted with MNC derived from IL-8-mobilized animals was 86% (P < .01). Anti-LFA–1 antibodies did not interfere with stem cell homing, as transplantation of IL-8-mobilized blood MNC, incubated in vitro with these antibodies resulted in 100% radioprotection. We conclude that anti–LFA-1 antibodies completely prevent the rapid mobilization of colony-forming cells and of cells with radioprotective capacity induced by IL-8. These results indicate a major role for the β2-integrin LFA-1 in the IL-8–induced mobilization of hematopoietic stem cells.
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Stewart, M. P., C. Cabanas y N. Hogg. "T cell adhesion to intercellular adhesion molecule-1 (ICAM-1) is controlled by cell spreading and the activation of integrin LFA-1." Journal of Immunology 156, n.º 5 (1 de marzo de 1996): 1810–17. http://dx.doi.org/10.4049/jimmunol.156.5.1810.
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Abstract Many leukocyte integrins require activation before they can adhere to their ligands. For example, stimulation of T cells enables the integrin LFA-1 to bind to ligand. This study compares two well known protocols for inducing T cell LFA-1 mediated adhesion to intercellular adhesion molecule-1 (ICAM)-1. We how that treatment with high concentrations of the divalent cation Mg2+ induces a high affinity state of LFA-1, which is reflected in the binding of soluble ICAM-1 and correlates with the expression of the epitope recognized by mAb 24. The second stimulation protocol with the phorbol ester phorbol-12,13-dibutyrate (PDBu) does not induce a high affinity state of LFA-1, and in this situation, adhesion is dependent on cell spreading and intracellular events involving protein kinase C, [Ca2+]i, and actin polymerization. These low affinity LFA-1 receptors are responsible for the initial contact with immobilized ligand because, unlike the Mg2+-stimulated receptors, adhesion is not blocked by soluble ICAM-1. Finally, we used a third method of inducing LFA-1-mediated adhesion by stimulation of T cells through the TCR/CD3 complex. This procedure, which is considered to be a more physiologic trigger for LFA-1 activation, resembles the phorbol ester protocol in that high affinity LFA-1 receptors are not induced and cell adhesion depends on involvement of the cytoskeleton and cell spreading.
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Morin, Nicole A., Patrick W. Oakes, Young-Min Hyun, Dooyoung Lee, Y. Eugene Chin, Michael R. King, Timothy A. Springer et al. "Nonmuscle myosin heavy chain IIA mediates integrin LFA-1 de-adhesion during T lymphocyte migration". Journal of Experimental Medicine 205, n.º 1 (14 de enero de 2008): 195–205. http://dx.doi.org/10.1084/jem.20071543.
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Precise spatial and temporal regulation of cell adhesion and de-adhesion is critical for dynamic lymphocyte migration. Although a great deal of information has been learned about integrin lymphocyte function–associated antigen (LFA)-1 adhesion, the mechanism that regulates efficient LFA-1 de-adhesion from intercellular adhesion molecule (ICAM)-1 during T lymphocyte migration is unknown. Here, we show that nonmuscle myosin heavy chain IIA (MyH9) is recruited to LFA-1 at the uropod of migrating T lymphocytes, and inhibition of the association of MyH9 with LFA-1 results in extreme uropod elongation, defective tail detachment, and decreased lymphocyte migration on ICAM-1, without affecting LFA-1 activation by chemokine CXCL-12. This defect was reversed by a small molecule antagonist that inhibits both LFA-1 affinity and avidity regulation, but not by an antagonist that inhibits only affinity regulation. Total internal reflection fluorescence microscopy of the contact zone between migrating T lymphocytes and ICAM-1 substrate revealed that inactive LFA-1 is selectively localized to the posterior of polarized T lymphocytes, whereas active LFA-1 is localized to their anterior. Thus, during T lymphocyte migration, uropodal adhesion depends on LFA-1 avidity, where MyH9 serves as a key mechanical link between LFA-1 and the cytoskeleton that is critical for LFA-1 de-adhesion.
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Margraf, Andreas, Giulia Germena, Hannes C. A. Drexler, Jan Rossaint, Nadine Ludwig, Barbara Prystaj, Sina Mersmann et al. "The integrin-linked kinase is required for chemokine-triggered high-affinity conformation of the neutrophil β2-integrin LFA-1". Blood 136, n.º 19 (5 de noviembre de 2020): 2200–2205. http://dx.doi.org/10.1182/blood.2020004948.
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Abstract Neutrophil adhesion and extravasation into tissue at sites of injury or infection depend on binding of the integrin lymphocyte function–associated antigen 1 (LFA-1) to ICAM-1 expressed on activated endothelial cells. The activation-dependent conformational change of LFA-1 to the high-affinity conformation (H+) requires kindlin-3 binding to the β2-integrin cytoplasmic domain. Here we show that genetic deletion of the known kindlin interactor integrin-linked kinase (ILK) impaired neutrophil adhesion and extravasation in the cremaster muscle and in a clinically relevant model of renal ischemia reperfusion injury. Using in vitro microfluidic adhesion chambers and conformation-specific antibodies, we show that knockdown of ILK in HL-60 cells reduced the conformational change of β2-integrins to the H+ conformation. Mechanistically, we found that ILK was required for protein kinase C (PKC) membrane targeting and chemokine-induced upregulation of its kinase activity. Moreover, PKC-α deficiency also resulted in impaired leukocyte adhesion in bone marrow chimeric mice. Mass spectrometric and western blot analyses revealed stimulation- and ILK-dependent phosphorylation of kindlin-3 upon activation. In summary, our data indicate an important role of ILK in kindlin-3–dependent conformational activation of LFA-1.
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Lee, Seung-Hyo, Farrah Kheradmand y David Corry. "Developmental Control of Integrin Expression Regulates T Helper-2 Effector Homing (99.6)". Journal of Immunology 178, n.º 1_Supplement (1 de abril de 2007): S195. http://dx.doi.org/10.4049/jimmunol.178.supp.99.6.
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Abstract Integrin CD18, a component of the lymphocyte function-associated antigen-1 (LFA-1) complex that also includes CD11a, is essential for Th2, but not Th1, cell homing, but the explanation for this phenomenon remains obscure. Here, we investigate the mechanism by which Th2 effector responses require the LFA-1 complex. CD11a-deficient T cells showed normal in vitro differentiation and function. However, Th2 cell-dependent allergic lung disease was markedly reduced in CD11a null mice and wild type mice given LFA-1 inhibitors, whereas control of infection with Leishmania major, a Th1-dependent response, was enhanced. In both disease models, recruitment of IL-4−, but not IFN-g, secreting cells to relevant organs was impaired, as was adhesion of Th2 cells in vitro. These diverse findings were explained by the markedly reduced expression of CD29, an alternate homing integrin, on Th2, but not Th1, cells, which precludes Th2 homing in the absence of CD11a. Thus, murine Th1 and Th2 cells utilize distinct integrins for homing, suggesting novel opportunities for integrin-based therapeutic intervention in diverse human ailments.
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Mobley, JL, E. Ennis y Y. Shimizu. "Differential activation-dependent regulation of integrin function in cultured human T-leukemic cell lines". Blood 83, n.º 4 (15 de febrero de 1994): 1039–50. http://dx.doi.org/10.1182/blood.v83.4.1039.1039.
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Abstract T lymphocytes isolated from human peripheral blood express beta 1 (VLA) and LFA-1 integrins, but strong binding to integrin ligands occurs only after the delivery of an activation stimulus to the T cell. To gain further insight into activation-dependent regulation of integrin function, we have analyzed integrin activity on three different T- leukemic cell lines: Jurkat, CEM, and H9. This analysis shows important mechanistic differences in integrin regulation. First, phorbol ester treatment results in increased beta 1 integrin-dependent adhesion of both Jurkat and CEM cells to fibronectin, but decreased adhesion of H9 cells. Second, certain activation stimuli that upregulate beta 1 integrin activity in peripheral T cells are nonfunctional in these T-cell lines. Third, analysis of a panel of Jurkat mutants lacking surface expression of CD2 and/or CD3 shows that CD2-mediated upregulation of beta 1 integrin activity is dependent on expression of CD3, whereas CD28-mediated upregulation is not dependent on either CD2 or CD3 expression. Fourth, all T-cell lines tested show an inability to adhere to purified ICAM-1 via LFA-1. The selective alterations in integrin regulation in these cell lines relative to peripheral blood T cells provide important insights into the intracellular processes involved in integrin activation.
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Mobley, JL, E. Ennis y Y. Shimizu. "Differential activation-dependent regulation of integrin function in cultured human T-leukemic cell lines". Blood 83, n.º 4 (15 de febrero de 1994): 1039–50. http://dx.doi.org/10.1182/blood.v83.4.1039.bloodjournal8341039.
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T lymphocytes isolated from human peripheral blood express beta 1 (VLA) and LFA-1 integrins, but strong binding to integrin ligands occurs only after the delivery of an activation stimulus to the T cell. To gain further insight into activation-dependent regulation of integrin function, we have analyzed integrin activity on three different T- leukemic cell lines: Jurkat, CEM, and H9. This analysis shows important mechanistic differences in integrin regulation. First, phorbol ester treatment results in increased beta 1 integrin-dependent adhesion of both Jurkat and CEM cells to fibronectin, but decreased adhesion of H9 cells. Second, certain activation stimuli that upregulate beta 1 integrin activity in peripheral T cells are nonfunctional in these T-cell lines. Third, analysis of a panel of Jurkat mutants lacking surface expression of CD2 and/or CD3 shows that CD2-mediated upregulation of beta 1 integrin activity is dependent on expression of CD3, whereas CD28-mediated upregulation is not dependent on either CD2 or CD3 expression. Fourth, all T-cell lines tested show an inability to adhere to purified ICAM-1 via LFA-1. The selective alterations in integrin regulation in these cell lines relative to peripheral blood T cells provide important insights into the intracellular processes involved in integrin activation.
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Issekutz, T. B. "In vivo blood monocyte migration to acute inflammatory reactions, IL-1 alpha, TNF-alpha, IFN-gamma, and C5a utilizes LFA-1, Mac-1, and VLA-4. The relative importance of each integrin." Journal of Immunology 154, n.º 12 (15 de junio de 1995): 6533–40. http://dx.doi.org/10.4049/jimmunol.154.12.6533.
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Abstract The role of the monocyte integrins, Mac-1, LFA-1, and VLA-4, on the adhesion of rat blood monocytes to rat microvascular endothelial cells in vitro and the importance of these receptors in monocyte migration to inflammation in vivo were evaluated. Monocyte adhesion to cytokine (IL-1, IFN-gamma, and TNF-alpha)-stimulated endothelial cells was mediated by Mac-1, LFA-1, and VLA-4, but Mac-1 appeared to be less important than LFA-1 or VLA-4. After i.v. injection, large numbers of 51Cr-labeled blood monocytes migrated within 2 h to dermal inflammatory sites induced by C5a, IL-1 alpha, IFN-gamma, TNF-alpha, LPS, and poly inosinic:cytidylic acid. Anti-Mac-1 mAb treatment had no effect, whereas anti-LFA-1 inhibited migration to C5a and the cytokines by 20 to 40%. Blocking both Mac-1 and LFA-1 decreased monocyte accumulation by 50 to 70% to all stimuli. Anti-VLA-4 inhibited monocyte migration to IL-1 alpha, IFN-gamma, TNF-alpha, and LPS, but not to C5a. Combining anti-Mac-1 with anti-VLA-4 did not increase this inhibition, whereas blocking VLA-4 and LFA-1 together further suppressed (60-85%) migration. Combined treatment with mAb to all three integrins inhibited > 98% of the monocyte migration to the inflammatory stimuli. In conclusion: 1) 51Cr blood monocytes can be used to quantify monocyte migration to inflammatory reactions in the rat. 2) Monocytes use Mac-1, LFA-1, and VLA-4 for in vitro adhesion and in vivo migration to cutaneous inflammation, and these integrins are essential for normal migration because blockade of all three virtually abolishes monocyte accumulation. 3) Mac-1 plays a less important role than LFA-1, as LFA-1 appears to substitute for Mac-1, and VLA-4 and LFA-1 can mediate much of the adhesion and migration. 4) The initiating inflammatory stimulus also modifies monocyte integrin usage, supporting the multistep combinatorial model of leukocyte extravasation.
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Weber, C., C. F. Lu, J. M. Casasnovas y T. A. Springer. "Role of alpha L beta 2 integrin avidity in transendothelial chemotaxis of mononuclear cells." Journal of Immunology 159, n.º 8 (15 de octubre de 1997): 3968–75. http://dx.doi.org/10.4049/jimmunol.159.8.3968.
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Abstract The leukocyte integrin alpha L beta 2 (LFA-1) is important in transendothelial migration. Since it is not fully understood how LFA-1 mediates transmigration, we studied the effects of alpha L and beta 2 cytoplasmic domain mutants that alter LFA-1 adhesiveness for intercellular adhesion molecule-1. Monocyte chemotactic protein-1 (MCP-1) induced LFA-1-dependent transendothelial migration of Jurkat and J-beta 2.7 transfectants coexpressing the MCP-1 receptor CCR2B and wild-type alpha L. No transendothelial chemotaxis was observed with truncation mutants of the alpha L cytoplasmic tail, which rendered LFA-1 constitutively active or locked LFA-1 in a low avidity state unresponsive to cellular activation. Moreover, transendothelial chemotaxis of lymphoblastoid SLA transfectants was abolished by truncation of the beta 2 cytoplasmic domain, but not by mutation of its TTT motif, which is important in phorbol ester-induced adhesion. These data indicate that transmigration may require both alpha L and beta 2 cytoplasmic domains. We further show that MCP-1-induced transendothelial chemotaxis of PBMC was inhibited by sustained activation of LFA-1 with Mn2+ or a stimulatory mAb to beta 2. Dimeric soluble intercellular adhesion molecule-1 also reduced transendothelial chemotaxis of PBMC. Taken together, our data suggest that transendothelial chemotaxis of mononuclear cells may involve dynamic changes in LFA-1 avidity.
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Grönholm, Mikaela, Farhana Jahan, Ekaterina A. Bryushkova, Sudarrshan Madhavan, Francesca Aglialoro, Laura Soto Hinojosa, Liisa M. Uotila y Carl G. Gahmberg. "LFA-1 integrin antibodies inhibit leukocyte α4β1–mediated adhesion by intracellular signaling". Blood 128, n.º 9 (1 de septiembre de 2016): 1270–81. http://dx.doi.org/10.1182/blood-2016-03-705160.
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Paccani, Silvia Rossi, Francesca Finetti, Marilyne Davi, Laura Patrussi, Mario M. D'Elios, Daniel Ladant y Cosima T. Baldari. "The Bordetella pertussis adenylate cyclase toxin binds to T cells via LFA-1 and induces its disengagement from the immune synapse". Journal of Experimental Medicine 208, n.º 6 (16 de mayo de 2011): 1317–30. http://dx.doi.org/10.1084/jem.20101558.
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The Bordetella pertussis adenylate cyclase toxin (CyaA) assists infection by potently suppressing the host immune response. Although CyaA effectively targets T lymphocytes, its putative receptor on these cells is unknown. Here, we show that CyaA binds to T cells via the β2 integrin LFA-1 in its active conformation. CyaA clusters with LFA-1 at the immune synapse (IS), from which it induces the premature disengagement of LFA-1 concomitant with the dissipation of talin, which tethers the integrin to the underlying actin cytoskeleton. The CyaA-induced redistribution of LFA-1 was cAMP- and protein kinase A (PKA)–dependent. These results not only identify LFA-1 as a CyaA receptor on T cells but unveil a novel mechanism of immunosuppression whereby the toxin parasitizes its interaction with LFA-1 to inhibit signaling at the IS through the local production of cAMP. The data also provide novel insights into the role of cAMP/PKA signaling in controlling the dynamics of the IS.
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Edwards, BS, MS Curry, EA Southon, AS Chong y LH Jr Graf. "Evidence for a dithiol-activated signaling pathway in natural killer cell avidity regulation of leukocyte function antigen-1: structural requirements and relationship to phorbol ester- and CD16-triggered pathways". Blood 86, n.º 6 (15 de septiembre de 1995): 2288–301. http://dx.doi.org/10.1182/blood.v86.6.2288.bloodjournal8662288.
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Dithiothreitol (DTT) activation of the adhesive function of several different integrins suggests the existence of a common DTT-sensitive integrin regulatory element. Ui11/E3, a natural killer (NK) cell- resistant murine target cell line genetically engineered to constitutively express human intercellular adhesion molecule-1 (ICAM-1; CD54) was used in a flow cytometric experimental model to evaluate DTT effects on the NK cell integrin adhesion molecule, leukocyte function antigen-1 (LFA-1; alpha L beta 2, CD11a/CD18). DTT and several structurally related dithiol compounds elicited a dramatic elevation in conjugate formation that was dependent on target cell ICAM-1 expression, was blocked by LFA-1 alpha L or beta 2 chain-specific antibodies, and occurred in the absence of Ui11/E3 target cell exposure to DTT or quantitative changes in NK cell membrane LFA-1 expression. This avidity modulation of LFA-1 by DTT required actin polymerization, was abrogated by the protein kinase C inhibitor calphostin C, involved activities of calyculin A- and okadaic acid-sensitive serine/threonine protein phosphatases PP-1 and/or PP-2A but not geldanamycin-sensitive tyrosine kinases, and differed with respect to kinetics and enzyme inhibitor sensitivity from LFA-1 activation promoted by cross-linking of NK cell CD16 or phorbol ester treatment. A key structural feature of DTT was the presence of two thiol groups, both reduced but not physically adjacent as in the nonstimulatory dithiol, 2,3- dimercaptopropanol. LFA-1 activation was not because of DTT chelation of Ca2+ or Zn2+. Immunoblotting studies identified multiple NK cell plasma membrane-associated proteins to be reduced by DTT under LFA-1- activating conditions, but similar effects were also promoted by reducing agent treatments that failed to alter adhesive function. Direct chemical modification of LFA-1 seemed an unlikely basis of activation because (1) DTT activated LFA-1 in HSB2 T cells without detectable disulfide reduction in LFA-1 alpha L or beta 2 chains immunoprecipitated from these cells and (2) DTT treatment of NK cells did not hinder binding of KIM127 and KIM185, monoclonal antibodies that recognize epitopes in the potentially DTT-susceptible cysteine-rich domain of the beta 2 chain. Thus, these results extended the range of DTT-activatible integrins to include NK cell LFA-1 and characterized for the first time signaling-associated enzymatic activities involved in DTT activation of NK cell LFA-1. Moreover, they suggested that structural features of DTT, particularly SH group spatial positioning, are important in LFA-activation for reasons other than cation chelation or disulfide reduction.(ABSTRACT TRUNCATED AT 400 WORDS)
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Velders, Gerjo A., Johannes F. M. Pruijt, Perry Verzaal, Ronald van Os, Yvette van Kooyk, Carl G. Figdor, Evert-Jan F. M. de Kruijf, Roel Willemze y Willem E. Fibbe. "Enhancement of G-CSF–induced stem cell mobilization by antibodies against the β2 integrins LFA-1 and Mac-1". Blood 100, n.º 1 (1 de julio de 2002): 327–33. http://dx.doi.org/10.1182/blood.v100.1.327.
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Abstract The β2 integrins leukocyte function antigen-1 (LFA-1, CD11a) and macrophage antigen-1 (Mac-1, CD11b) have been reported to play a role in the attachment of CD34+ cells to stromal cells in the bone marrow. When administered prior to interleukin-8 (IL-8), anti–LFA-1 antibodies completely prevent the IL-8–induced mobilization of hematopoietic stem cells in mice. Here, we studied the role of anti-β2 integrin antibodies in granulocyte colony-stimulating factor (G-CSF)–induced mobilization of hematopoietic progenitor cells. Administration of antibodies against the α chain of LFA-1 or against the α chain of Mac-1 followed by daily injections of G-CSF for more than 1 day resulted in a significant enhancement of mobilization of hematopoietic progenitor cells when compared with mobilization induced by G-CSF alone. Also, the number of late (day 28) cobblestone area–forming cells in vitro was significantly higher after mobilization with anti–LFA-1 antibodies followed by 5 μg G-CSF for 5 days than with G-CSF alone (119 ± 34 days vs 17 ± 14 days), indicating mobilization of repopulating stem cells. Pretreatment with blocking antibodies to intercellular adhesion molecule-1 (ICAM-1; CD54), a ligand of LFA-1 and Mac-1, did not result in an effect on G-CSF–induced mobilization, suggesting that the enhancing effect required an interaction of the β2 integrins and one of their other ligands. Enhancement of mobilization was not observed in LFA-1–deficient (CD11a) mice, indicating that activated cells expressing LFA-1 mediate the synergistic effect, rather than LFA-1–mediated adhesion.
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Weber, K. S., M. R. York, T. A. Springer y L. B. Klickstein. "Characterization of lymphocyte function-associated antigen 1 (LFA-1)-deficient T cell lines: the alphaL and beta2 subunits are interdependent for cell surface expression." Journal of Immunology 158, n.º 1 (1 de enero de 1997): 273–79. http://dx.doi.org/10.4049/jimmunol.158.1.273.
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Abstract The leukocyte, or beta2, integrins are heterodimeric cell surface molecules that share a common beta subunit, and have unique alpha subunits. LFA-1 is the predominant beta2 integrin on lymphocytes, and plays an important role in many lymphocyte functions; however, most studies of the cytoplasmic regions of LFA-1 have been performed in transfected epithelial cells, such as COS, in part because no lymphoid cell lines deficient in the LFA-1 alpha subunit have been described. To address structure-function studies of beta2 integrins in relevant cell types, two T lymphoblastoid cell clones that completely lack cell surface LFA-1, J-(beta2).7 and SK-(beta2).7, derived from Jurkat and SKW3, respectively, were prepared by chemical mutagenesis and selection. Biosynthetic labeling and immunoprecipitation showed that the J-(beta2).7 clone did not translate any LFA-1 alpha subunit protein, while the SK-(beta2).7 cells did not synthesize any beta2 subunit protein. Northern blot analysis of poly(A+) RNA from these cells revealed an absence of the corresponding mRNA in each case. By transfection analysis, only the alpha subunit reconstituted LFA-1 expression in the J-(beta2).7 cells, while only the beta subunit restored cell surface LFA-1 expression in the SK-(beta2).7 cells. Functional studies with the parental cell lines, the J-(beta2).7 and SK-(beta2).7 cells, and the transfectants showed that all binding of Jurkat and SKW3 cells to purified ICAM-1 is mediated by LFA-1, and the reconstituted LFA-1 expressed by the J-(beta2).7 and SK-(beta2).7 transfected cells is regulated normally.
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Evans, Rachel, Annemarie C. Lellouch, Lena Svensson, Alison McDowall y Nancy Hogg. "The integrin LFA-1 signals through ZAP-70 to regulate expression of high-affinity LFA-1 on T lymphocytes". Blood 117, n.º 12 (24 de marzo de 2011): 3331–42. http://dx.doi.org/10.1182/blood-2010-06-289140.
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Abstract The integrin lymphocyte function-associated antigen 1 (LFA-1) controls many functions of T lymphocytes and is particularly essential during lymphocyte migration from blood into tissues. LFA-1 is considered to initiate “outside-in” signaling when bound to ligand intercellular adhesion molecule 1 (ICAM-1), but little is known about the proteins involved or where in the cell such LFA-1–mediated signaling might be operating. Here we show that LFA-1 is constitutively associated with the protein tyrosine kinases Lck and zeta chain–associated protein of 70 kDa (ZAP-70). When LFA-1 binds ICAM-1, both kinases become phosphorylated and the consequence of kinase activation is the conversion of intermediate- to high-affinity LFA-1 and an increase in close contact with ICAM-1. In the polarized T lymphocyte, phospho-ZAP-70 is concentrated within a region of high-affinity LFA-1 that includes talin and encompasses the lamella/lamellipodial interface as well as further back in the cell. Deficiency of ZAP-70 through inhibition or knockdown in T lymphocytes decreases the speed of migration on ICAM-1, as well as reducing firm adhesion under shear-flow conditions. Through its control of high-affinity LFA-1, the LFA-1/Lck/ZAP-70 complex is in position to initiate the rapid adhesion strengthening and migration necessary for T-lymphocyte responses when stimulated vasculature is encountered at sites of infection or injury.
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Kim, Minsoo, Christopher V. Carman, Wei Yang, Azucena Salas y Timothy A. Springer. "The primacy of affinity over clustering in regulation of adhesiveness of the integrin αLβ2". Journal of Cell Biology 167, n.º 6 (20 de diciembre de 2004): 1241–53. http://dx.doi.org/10.1083/jcb.200404160.
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Dynamic regulation of integrin adhesiveness is required for immune cell–cell interactions and leukocyte migration. Here, we investigate the relationship between cell adhesion and integrin microclustering as measured by fluorescence resonance energy transfer, and macroclustering as measured by high resolution fluorescence microscopy. Stimuli that activate adhesion through leukocyte function–associated molecule-1 (LFA-1) failed to alter clustering of LFA-1 in the absence of ligand. Binding of monomeric intercellular adhesion molecule-1 (ICAM-1) induced profound changes in the conformation of LFA-1 but did not alter clustering, whereas binding of ICAM-1 oligomers induced significant microclustering. Increased diffusivity in the membrane by cytoskeleton-disrupting agents was sufficient to drive adhesion in the absence of affinity modulation and was associated with a greater accumulation of LFA-1 to the zone of adhesion, but redistribution did not precede cell adhesion. Disruption of conformational communication within the extracellular domain of LFA-1 blocked adhesion stimulated by affinity-modulating agents, but not adhesion stimulated by cytoskeleton-disrupting agents. Thus, LFA-1 clustering does not precede ligand binding, and instead functions in adhesion strengthening after binding to multivalent ligands.
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Wu, Xing, Tao Yu, Daniel C. Bullard y Dennis F. Kucik. "SDF-1α (CXCL12) regulation of lateral mobility contributes to activation of LFA-1 adhesion". American Journal of Physiology-Cell Physiology 303, n.º 6 (15 de septiembre de 2012): C666—C672. http://dx.doi.org/10.1152/ajpcell.00190.2012.
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Regulation of integrin activity enables leukocytes to circulate freely, avoiding inappropriate adhesion while maintaining the ability to adhere quickly at sites of infection or inflammation. This regulation involves at least two components: affinity for ligand and affinity-independent avidity effects such as lateral mobility. Using lymphocyte function associated antigen-1 (LFA-1) as a model, we investigated the role of integrin release from cytoskeletal motion constraints in response to the chemokine stromal cell-derived factor-1 (SDF-1α) in this process. All experiments were done in primary T cells to avoid nonphysiological activation processes often seen with the use of cell lines. We found that SDF-1α releases LFA-1 from cytoskeletal constraints as effectively as does cytochalasin D. The resultant increased diffusion is correlated with a robust increase in LFA-1-mediated adhesion under physiological shear stress. We further investigated the role of the highly conserved GFFKR sequence in the LFA-1 cytoplasmic domain. We report that the GFFKR sequence is both necessary and sufficient for regulation of the SDF-1α-triggered proadhesive release from cytoskeleton interactions. While this does not address the role of transient SDF-1α-induced conformational changes in the activation process, these results strongly suggest that any model of chemokine-induced LFA-1 activation must take into account chemokine-induced integrin lateral mobility. In addition, these results have ramifications for models of differential binding of LFA-1 to surface-bound vs. soluble intercellular adhesion molecule-1.
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Lub, M., Y. van Kooyk, S. J. van Vliet y C. G. Figdor. "Dual role of the actin cytoskeleton in regulating cell adhesion mediated by the integrin lymphocyte function-associated molecule-1." Molecular Biology of the Cell 8, n.º 2 (febrero de 1997): 341–51. http://dx.doi.org/10.1091/mbc.8.2.341.
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Intracellular signals are required to activate the leukocyte-specific adhesion receptor lymphocyte function-associated molecule-1 (LFA-1; CD11a/CD18) to bind its ligand, intracellular adhesion molecule-1 (ICAM-1). In this study, we investigated the role of the cytoskeleton in LFA-1 activation and demonstrate that filamentous actin (F-actin) can both enhance and inhibit LFA-1-mediated adhesion, depending on the distribution of LFA-1 on the cell surface. We observed that LFA-1 is already clustered on the cell surface of interleukin-2/phytohemagglutinin-activated lymphocytes. These cells bind strongly ICAM-1 and disruption of the actin cytoskeleton inhibits adhesion. In contrast to interleukin-2/phytohemagglutinin-activated peripheral blood lymphocytes, resting lymphocytes, which display a homogenous cell surface distribution of LFA-1, respond poorly to intracellular signals to bind ICAM-1, unless the actin cytoskeleton is disrupted. On resting peripheral blood lymphocytes, uncoupling of LFA-1 from the actin cytoskeleton induces clustering of LFA-1 and this, along with induction of a high-affinity form of LFA-1, via "inside-out" signaling, results in enhanced binding to ICAM-1, which is dependent on intact intermediate filaments, microtubules, and metabolic energy. We hypothesize that linkage of LFA-1 to cytoskeletal elements prevents movement of LFA-1 over the cell surface, thus inhibiting clustering and strong ligand binding. Release from these cytoskeletal elements allows lateral movement and activation of LFA-1, resulting in ligand binding and "outside-in" signaling, that subsequently stimulates actin polymerization and stabilizes cell adhesion.
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Lu, C. F. y T. A. Springer. "The alpha subunit cytoplasmic domain regulates the assembly and adhesiveness of integrin lymphocyte function-associated antigen-1." Journal of Immunology 159, n.º 1 (1 de julio de 1997): 268–78. http://dx.doi.org/10.4049/jimmunol.159.1.268.
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Abstract The integrin LFA-1 mediates activation-dependent leukocyte adhesion. The beta subunit cytoplasmic domain has been demonstrated previously to modulate the adhesiveness of LFA-1. To investigate whether the alpha subunit cytoplasmic domain is also involved in the regulation of LFA-1-adhesive function, we stably expressed cytoplasmic domain truncated forms of the alpha subunit in a Jurkat mutant (Jurkat-beta2.7) deficient in the endogenous LFA-1 alpha subunit and in K562 cells. Clones expressing similar levels of cell surface LFA-1 were tested for their ability to bind to immobilized ICAM-1. Truncation of the alpha subunit cytoplasmic domain before, but not after, the conserved GFFKR sequence motif resulted in constitutive ICAM-1 binding of both Jurkat-beta2.7 and K562 transfectants. However, truncation after the GFFKR motif reduced sensitivity to stimulation by PMA or stimulatory Abs. Internal deletion of the GFFKR motif, or point mutations of the Gly (G), the two Phe (F), or the Arg (R) in the GFFKR motif to Ala (A) rendered LFA-1 constitutively active. Mutation of the Lys (K) did not affect LFA-1 adhesion to ICAM-1. These findings indicate that the GFFKR motif maintains the low adhesive state of LFA-1, possibly by restraining the receptor conformation. We further demonstrate that the alpha subunit cytoplasmic domain and the conserved GFFKR motif are also required for efficient formation of LFA-1 alphabeta heterodimers.
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Morikis, Vasilios Aris, Myung Hyun Jo, Taekjip Ha y Scott I. Simon. "Bond tension on neutrophil LFA-1 regulates membrane calcium flux from the outside-in". Journal of Immunology 202, n.º 1_Supplement (1 de mayo de 2019): 64.13. http://dx.doi.org/10.4049/jimmunol.202.supp.64.13.
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Abstract Recruitment of neutrophils in appropriate numbers at vascular sites of inflammation is critical for innate immune surveillance. LFA-1 adhesive bonds that support neutrophil deceleration and arrest under fluid shear, also function to mechanotransduce signals that spatially localize calcium flux necessary to guide transendothelial migration. We set out to characterize how bond tension acting on high-affinity LFA-1/ICAM-1 bonds transduce intracellular signaling in a manner proportional to the shear force acting on adherent cells. A sequential set of events beginning with a shift to high affinity of LFA-1 that binds ICAM-1, a buildup of tension, and assembly of adaptor proteins that terminate in spatial linkage to the CRAC channel Orai-1. Utilizing microfluidic vascular mimetic flow chamber, we observed that force catalyzed integrin clustering and calcium flux in a Kindlin-3 dependent manner. Kindlin-3 has a dual role as a mechanical anchor that links to adaptors that assemble Orai-1 mediated calcium influx and as a support for LFA-1 membrane clustering. RACK1 deficient neutrophils retained the capacity for integrin clustering but lacked calcium signaling. Utilizing a molecular platform that regulates the force acting on LFA-1 bonds we determined the characteristic bond tension necessary to transduce signaling. Forces between 33 and 54 pN were sufficient to support LFA-1 binding to Kindlin-3 and promote integrin clustering. As this characteristic force completed a macromolecular complex constituted of RACK1/Orai1 signaling complex competent to transduce calcium influx. We identify a molecular circuit catalyzed by a well-defined force that may represent the necessity to assemble Kindlin-3 to intracellular LFA-1 domains.
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Wen, Lai, Alex Marki, Zhihao Wang, Marco Orecchioni, Jeffrey Makings, Kenneth Kim, William B. Kiosses, Zbigniew Mikulski y Klaus Ley. "A new β2 integrin activation reporter mouse reveals localized intra- and extra-vascular neutrophil integrin activation in vivo". Journal of Immunology 208, n.º 1_Supplement (1 de mayo de 2022): 105.07. http://dx.doi.org/10.4049/jimmunol.208.supp.105.07.
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Abstract β2 integrins (LFA-1, Mac-1, CD11c-CD18, and CD11d-CD18) are leukocyte-specific adhesion receptors that play critical roles in leukocyte recruitment, as well as other immunological processes such as phagocytosis and immunological synapse formation. Adhesion of leukocytes to other cells such as endothelial cells are regulated by integrin affinity changes for their ligands (“activation”). Human β2 integrin activation can be detected by reporter antibodies including mAb24 and KIM127. No such activation epitopes are known in mouse β2 integrins. Because of the lack of mouse β2 integrin activation reporter antibodies, nothing is known about β2 integrin activation in vivo. Here, we generated a humanized β2 integrin knockin mouse by targeting the human β2 integrin coding sequence into the mouse Itgb2 locus. We show that this enables imaging of β2 integrin activation using the KIM127 (extension conformation) and mAb24 (high affinity) reporter antibodies. Human β2 pairs with the mouse integrin α chains, yielding normal expression of the β2 integrins LFA-1, Mac-1 and CD11c-CD18 in all major leukocyte populations. Using a CXCL1-induced acute inflammation model, we uncovered the dynamics and subcellular localization of β2 integrin activation in arresting neutrophils in vivo in venules of the mouse cremaster muscle. Activated integrins in arresting neutrophils in vivo are concentrated at the interface of neutrophils and the endothelium at the rear side of neutrophils facing against the blood flow. In a high-dose lipopolysaccharide (LPS) model, we found that β2 integrins are activated in association with elevated neutrophil adhesion in lung and liver. Thus, these mice, for the first time, enable studies into β2 integrin activation in vivo. This work was supported by grants from the National Institutes of Health, USA (HL078784 to K.L.) and a Postdoctoral Fellowship (19POST34450228 to L.W.) from the American Heart Association, USA.
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Choi, Eun Young, Valeria V. Orlova, Susanna C. Fagerholm, Susanna M. Nurmi, Li Zhang, Christie M. Ballantyne, Carl G. Gahmberg y Triantafyllos Chavakis. "Regulation of LFA-1–dependent inflammatory cell recruitment by Cbl-b and 14-3-3 proteins". Blood 111, n.º 7 (1 de abril de 2008): 3607–14. http://dx.doi.org/10.1182/blood-2007-07-103077.
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Abstract Inside-out signaling regulation of the β2-integrin leukocyte function–associated antigen-1 (LFA-1) by different cytoplasmic proteins, including 14-3-3 proteins, is essential for adhesion and migration of immune cells. Here, we identify a new pathway for the regulation of LFA-1 activity by Cbl-b, an adapter molecule and ubiquitin ligase that modulates several signaling pathways. Cbl-b−/− mice displayed increased macrophage recruitment in thioglycollate-induced peritonitis, which was attributed to Cbl-b deficiency in macrophages, as assessed by bone marrow chimera experiments. In vitro, Cbl-b−/− bone marrow–derived mononuclear phagocytes (BMDMs) displayed increased adhesion to endothelial cells. Activation of LFA-1 in Cbl-b–deficient cells was responsible for their increased endothelial adhesion in vitro and peritoneal recruitment in vivo, as the phenotype of Cbl-b deficiency was reversed in Cbl-b−/−LFA-1−/− mice. Consistently, LFA-1–mediated adhesion of BMDM to ICAM-1 but not VLA-4–mediated adhesion to VCAM-1 was enhanced by Cbl-b deficiency. Cbl-b deficiency resulted in increased phosphorylation of T758 in the β2-chain of LFA-1 and thereby in enhanced association of 14-3-3β protein with the β2-chain, leading to activation of LFA-1. Consistently, disruption of the 14-3-3/β2-integrin interaction abrogated the enhanced ICAM-1 adhesion of Cbl-b−/− BMDMs. In conclusion, Cbl-b deficiency activates LFA-1 and LFA-1–mediated inflammatory cell recruitment by stimulating the interaction between the LFA-1 β-chain and 14-3-3 proteins.
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Pruijt, Johannes F. M., Yvette van Kooyk, Carl G. Figdor, Roel Willemze y Willem E. Fibbe. "Murine Hematopoietic Progenitor Cells With Colony-Forming or Radioprotective Capacity Lack Expression of the β2-Integrin LFA-1". Blood 93, n.º 1 (1 de enero de 1999): 107–12. http://dx.doi.org/10.1182/blood.v93.1.107.
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Abstract Recently, we have demonstrated that antibodies that block the function of the β2-integrin leukocyte function-associated antigen-1 (LFA-1) completely abrogate the rapid mobilization of hematopoietic progenitor cells (HPC) with colony-forming and radioprotective capacity induced by interleukin-8 (IL-8) in mice. These findings suggested a direct inhibitory effect of these antibodies on LFA-1–mediated transmigration of stem cells through the bone marrow endothelium. Therefore, we studied the expression and functional role of LFA-1 on murine HPC in vitro and in vivo. In steady state bone marrow ± 50% of the mononuclear cells (MNC) were LFA-1neg. Cultures of sorted cells, supplemented with granulocyte colony-stimulating factor (G-CSF)/granulocyte-macrophage colony-stimulating factor (GM-CSF)/IL-1/IL-3/IL-6/stem cell factor (SCF) and erythropoietin (EPO) indicated that the LFA-1neg fraction contained the majority of the colony-forming cells (CFCs) (LFA-1neg 183 ± 62/7,500 cells v LFA-1pos 29 ± 17/7,500 cells,P < .001). We found that the radioprotective capacity resided almost exclusively in the LFA-1neg cell fraction, the radioprotection rate after transplantation of 103, 3 × 103, 104, and 3 × 104 cells being 63%, 90%, 100%, and 100% respectively. Hardly any radioprotection was obtained from LFA-1pos cells. Similarly, in cytokine (IL-8 and G-CSF)–mobilized blood, the LFA-1neg fraction, which comprised 5% to 10% of the MNC, contained the majority of the colony-forming cells, as well as almost all cells with radioprotective capacity. Subsequently, primitive bone marrow-derived HPC, represented by Wheat-germ-agglutinin (WGA)+/Lineage (Lin)−/Rhodamine (Rho)− sorted cells, were examined. More than 95% of the Rho− cells were LFA-1neg. Cultures of sorted cells showed that the LFA-1neg fraction contained all CFU. Transplantation of 150 Rho− LFA-1neg or up to 600 Rho−LFA-1pos cells protected 100% and 0% of lethally irradiated recipient mice, respectively. These results show that primitive murine HPC in steady-state bone marrow and of cytokine-mobilized blood do not express LFA-1.
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Pruijt, Johannes F. M., Yvette van Kooyk, Carl G. Figdor, Roel Willemze y Willem E. Fibbe. "Murine Hematopoietic Progenitor Cells With Colony-Forming or Radioprotective Capacity Lack Expression of the β2-Integrin LFA-1". Blood 93, n.º 1 (1 de enero de 1999): 107–12. http://dx.doi.org/10.1182/blood.v93.1.107.401k14_107_112.
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Recently, we have demonstrated that antibodies that block the function of the β2-integrin leukocyte function-associated antigen-1 (LFA-1) completely abrogate the rapid mobilization of hematopoietic progenitor cells (HPC) with colony-forming and radioprotective capacity induced by interleukin-8 (IL-8) in mice. These findings suggested a direct inhibitory effect of these antibodies on LFA-1–mediated transmigration of stem cells through the bone marrow endothelium. Therefore, we studied the expression and functional role of LFA-1 on murine HPC in vitro and in vivo. In steady state bone marrow ± 50% of the mononuclear cells (MNC) were LFA-1neg. Cultures of sorted cells, supplemented with granulocyte colony-stimulating factor (G-CSF)/granulocyte-macrophage colony-stimulating factor (GM-CSF)/IL-1/IL-3/IL-6/stem cell factor (SCF) and erythropoietin (EPO) indicated that the LFA-1neg fraction contained the majority of the colony-forming cells (CFCs) (LFA-1neg 183 ± 62/7,500 cells v LFA-1pos 29 ± 17/7,500 cells,P < .001). We found that the radioprotective capacity resided almost exclusively in the LFA-1neg cell fraction, the radioprotection rate after transplantation of 103, 3 × 103, 104, and 3 × 104 cells being 63%, 90%, 100%, and 100% respectively. Hardly any radioprotection was obtained from LFA-1pos cells. Similarly, in cytokine (IL-8 and G-CSF)–mobilized blood, the LFA-1neg fraction, which comprised 5% to 10% of the MNC, contained the majority of the colony-forming cells, as well as almost all cells with radioprotective capacity. Subsequently, primitive bone marrow-derived HPC, represented by Wheat-germ-agglutinin (WGA)+/Lineage (Lin)−/Rhodamine (Rho)− sorted cells, were examined. More than 95% of the Rho− cells were LFA-1neg. Cultures of sorted cells showed that the LFA-1neg fraction contained all CFU. Transplantation of 150 Rho− LFA-1neg or up to 600 Rho−LFA-1pos cells protected 100% and 0% of lethally irradiated recipient mice, respectively. These results show that primitive murine HPC in steady-state bone marrow and of cytokine-mobilized blood do not express LFA-1.
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Meijne, A. M., M. H. Driessens, G. La Riviere, D. Casey, C. A. Feltkamp y E. Roos. "LFA-1 integrin redistribution during T-cell hybridoma invasion of hepatocyte cultures and manganese-induced adhesion to ICAM-1". Journal of Cell Science 107, n.º 9 (1 de septiembre de 1994): 2557–66. http://dx.doi.org/10.1242/jcs.107.9.2557.
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We have reported previously that the integrin LFA-1 is essential for metastasis of T-cell hybridomas to the liver. We show here that hepatocytes isolated from normal non-inflamed rat liver express intercellular adhesion molecule-1 (ICAM-1) at the dorsal surface and more prominently at the lateral and substratum-adherent surfaces. Anti-rat ICAM-1 mAb inhibited adhesion of TAM8C4 T-cell hybridoma cells to hepatocytes. Invasion between hepatocytes was not affected, but this is probably due to lack of penetration of the mAb between the hepatocytes. In all hepatocyte-adherent TAM8C4 cells, LFA-1 was concentrated at the adhesion site. Redistribution of ICAM-1 to the interacting hepatocyte membrane was also seen, but only for part of the adherent TAM8C4 cells. LFA-1 was highly concentrated on pseudopods of invading TAM8C4 cells inserted between hepatocytes, and on the upper surface of invaded TAM8C4 cells located under the hepatocytes. ICAM-1 was concentrated in the hepatocyte membrane overlying TAM8C4 cells located underneath the monolayer. These results suggests that ICAM-1 is of major importance for liver invasion by these lymphoma cells. For optimal adhesion to ICAM-1, LFA-1 on T-cell hybridomas requires activation, which apparently occurs upon contact with cell layers that are invaded (G. La Riviere et al., J. Cell Sci. 107, 551–559, 1994). LFA-1 can be activated artificially by Mn2+. To study LFA-1 redistribution upon ICAM-1 interaction with higher resolution, we performed immuno-EM on cells before and after Mn(2+)-induced adhesion and spreading on immobilized ICAM-1. By immune fluorescence, LFA-1 was observed to redistribute to the ICAM-1-adherent surface, and to be concentrated in lamellipodia of spreading TAM8C4 cells. By immuno-EM, LFA-1 was localized in microclusters of approximately 10 gold particles. This was seen in cells fixed in suspension, and the size of these clusters did not change upon adhesion to ICAM-1. LFA-1 was present at high density in thin filopodia, but again in microclusters of similar size. Comparable results were obtained with a cytotoxic T-cell clone. We conclude that Mn(2+)-induced activation of LFA-1 is not associated with the formation or enlargement of LFA-1 clusters.
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Mace, Emily M., Jinyi Zhang, Katherine A. Siminovitch y Fumio Takei. "Elucidation of the integrin LFA-1–mediated signaling pathway of actin polarization in natural killer cells". Blood 116, n.º 8 (26 de agosto de 2010): 1272–79. http://dx.doi.org/10.1182/blood-2009-12-261487.
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Abstract The leukocyte integrin LFA-1 is critical for natural killer (NK) cell cytotoxicity as it mediates NK-cell adhesion to target cells and generates activating signals that lead to polarization of the actin cytoskeleton. However, the LFA-1–mediated signaling pathway is not fully understood. Here, we examined the subcellular localization of actin-associated proteins in wild-type, talin-deficient, and Wiskott-Aldrich Syndrome protein (WASP)–deficient NK cells bound to beads coated with the LFA-1 ligand intercellular adhesion molecule-1 (ICAM-1). In addition, we carried out coimmunoprecipitation analyses and also used a pharmacologic reagent to reduce the level of phosphatidylinositol-4,5-bisphosphate (PIP2). The results revealed the following signaling pathways. Upon ICAM-1 binding to LFA-1, talin redistributes to the site of LFA-1 ligation and initiates 2 signaling pathways. First, talin recruits the actin nucleating protein complex Arp2/3 via constitutive association of vinculin with talin and Arp2/3. Second, talin also associates with type I phosphatidylinositol 4-phosphate 5-kinase (PIPKI) and binding of LFA-1 to ICAM-1 results in localized increase in PIP2. This increase in PIP2 recruits WASP to the site of LFA-1 ligation where WASP promotes Arp2/3-mediated actin polymerization. These processes are critical for the initiation of NK cell–mediated cytotoxicity.
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Bell, Elaine D., Andrew P. May y David L. Simmons. "The Leukocyte Function-Associated Antigen-1 (LFA-1)-Binding Site on ICAM-3 Comprises Residues on Both Faces of the First Immunoglobulin Domain". Journal of Immunology 161, n.º 3 (1 de agosto de 1998): 1363–70. http://dx.doi.org/10.4049/jimmunol.161.3.1363.
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Abstract ICAM-3 (CD50), a member of the Ig superfamily, is a major ligand for the leukocyte integrin LFA-1 (CD11a/CD18). This interaction represents one of several Ig superfamily/integrin ligand-receptor pairs that have been described to date. ICAM-3 is highly expressed on resting leukocytes and on APCs. In addition to an adhesive function, ICAM-3 can act as a signal-transducing molecule on T cells, providing a costimulatory signal for cell proliferation. Eighteen point mutations in ICAM-3 were generated, and residues important for binding of functional blocking Abs were identified. Mutation of seven of the residues reduced or abrogated adhesion to LFA-1, including three residues that are located on strand A of the ABED face of domain 1. In contrast, extensive mutagenesis analysis of ICAM-1 has shown that only residues on the GFC face interact with LFA-1. Our results provide evidence for a more extensive binding interface between ICAM-3 and LFA-1 than has previously been described. ICAM-3 appears to be unique among the ICAMs in utilizing residues on both faces of domain 1 for interaction with its ligand LFA-1.
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Comrie, William A., Alexander Babich y Janis K. Burkhardt. "F-actin flow drives affinity maturation and spatial organization of LFA-1 at the immunological synapse". Journal of Cell Biology 208, n.º 4 (9 de febrero de 2015): 475–91. http://dx.doi.org/10.1083/jcb.201406121.
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Integrin-dependent interactions between T cells and antigen-presenting cells are vital for proper T cell activation, effector function, and memory. Regulation of integrin function occurs via conformational change, which modulates ligand affinity, and receptor clustering, which modulates valency. Here, we show that conformational intermediates of leukocyte functional antigen 1 (LFA-1) form a concentric array at the immunological synapse. Using an inhibitor cocktail to arrest F-actin dynamics, we show that organization of this array depends on F-actin flow and ligand mobility. Furthermore, F-actin flow is critical for maintaining the high affinity conformation of LFA-1, for increasing valency by recruiting LFA-1 to the immunological synapse, and ultimately for promoting intracellular cell adhesion molecule 1 (ICAM-1) binding. Finally, we show that F-actin forces are opposed by immobilized ICAM-1, which triggers LFA-1 activation through a combination of induced fit and tension-based mechanisms. Our data provide direct support for a model in which the T cell actin network generates mechanical forces that regulate LFA-1 activity at the immunological synapse.
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Petruzzelli, Lilli, Lisa Maduzia y Timothy A. Springer. "Differential Requirements for LFA-1 Binding to ICAM-1 and LFA-1-Mediated Cell Aggregation". Journal of Immunology 160, n.º 9 (1 de mayo de 1998): 4208–16. http://dx.doi.org/10.4049/jimmunol.160.9.4208.
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Abstract Cellular adhesion through the β2 integrin lymphocyte function-associated Ag (LFA)-1 is a complex event involving activation, ligand binding, and cell shape changes that ultimately result in enhanced adhesion. In this report we define requirements for ligand binding and post receptor signaling by comparing two mechanisms of activation of LFA-1: 1) inside-out signaling and 2) direct activation by the β2 Ab, CBR LFA-1/2. Our results demonstrate that activation of LFA-1 binding to ICAM-1 by CBR LFA-1/2, in contrast to inside-out signaling mechanisms, does not require protein kinase C activation or protein phosphatase 2A activity nor is it affected by agents that interfere with reorganization of the cytoskeleton. Inhibition of protein tyrosine kinase activity does not affect ICAM-1 binding by either mechanism of activation. However, activation by either mode does require the presence of the β cytoplasmic domain; deletion of the C-terminal phenylalanine or the five amino acid stretch between 756–762 abolished activation of LFA-1. This, combined with the observation that intracellular energy pools must be preserved, implicates the β cytoplasmic domain in a key energy-dependent conformational change in LFA-1 that is required to achieve enhanced ligand binding. Post ligand binding events induced by both PMA and Ab stimulation, as measured by homotypic aggregation, require protein tyrosine kinase, phosphatase, and RhoA activities. By examining both ligand binding and aggregation, we have been able to dissect the signaling components critical in the multistep process of LFA-1-mediated cellular adhesion.
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Bardhan, Kankana, Nikolaos Patsoukis, Alexandra Plessa, Niko Tsopoulidis, Duygu Sari, Lequn Li y Vassiliki A. Boussiotis. "Rap1-GTP Augments TGF-b-Mediated Signaling in T Lymphocytes Via a Mechanism Dependent on the b Chain of LFA-1 Integrin". Blood 126, n.º 23 (3 de diciembre de 2015): 3422. http://dx.doi.org/10.1182/blood.v126.23.3422.3422.
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Abstract Integrin-mediated adhesion of lymphocytes to antigen presenting cells (APCs) is a critical event linking innate and adaptive immunity. Integrins function as bidirectional receptors and can transmit signals from both sides of the plasma membrane, a property referred to as inside-out and outside-in signaling. Lymphocyte adhesion to APC is mainly accomplished through the principle adhesion molecule on the lymphocyte surface, the lymphocyte functional antigen 1 (LFA-1), which binds to intercellular adhesion molecule 1 (ICAM-1) on the surface of APCs. In order to mediate its function, LFA-1 must be activated via a process, which results in conformation changes of the receptor that extends the ectodomains of the α and β chains leading to a high affinity state. Among the few signaling molecules that have been implicated in integrin activation in hematopoietic cells are the small GTPase Rap1A (thereafter named Rap1) and its downstream effectors RapL and RIAM. In response to Rap1-GTP, RapL regulates LFA-1 activation by interacting with the integrin α chain, whereas RIAM mediates recruitment of talin to the cytoplasmic tail of the β chain leading to its conformational change to the high affinity state. To understand the role of Rap1 in T cell responses we generated transgenic (Tg) mice that selectively express the active, GTP-bound Rap1 mutant Rap1E63 in mature T cells. Rap1E63-Tg and littermate control mice had no statistically significant difference in absolute thymocyte numbers and differentiation profiles. In contrast, in peripheral lymphoid organs, Rap1E63-Tg mice had a significant reduction in total T cells but a 4-fold increase in the CD4+ CD103+ T cell fraction. CD103 (also known as αEβ7 integrin) defines a subset of peripherally generated Treg with potent suppressive function. TGF-β is the strongest stimulus for induction of CD103 (αEβ7). To examine whether Rap1-GTP can affect TGF-β-mediated signaling in T cells, we used stable Jurkat T cell lines expressing GTP-bound Rap1 mutant, Rap1E63, or Jurkat T cell lines in which the endogenous Rap1 was depleted by shRNA (Rap1-KD), and also primary T cells from Rap1E63-Tg mice and Rap1-KO mice. After interaction with two membrane-bound receptors, TGF-βRI and II, TGF-β propagates downstream signaling via the Smad family transcription factors. Incubation of Rap1E63 Jurkat T cells with TGF-β resulted in enhanced and sustained phosphorylation of Smad2 and Smad3, which was observed with very low concentrations of TGF-β that were incapable of inducing detectable phosphorylation of Smads in control Jurkat T cells. In contrast, diminished level and duration of Smad2 and Smad3 phosphorylation was observed in Rap1-KD Jurkat T cells. Similar patterns of responses to those observed in Rap1E63 Jurkat T cells and in Rap1-KD Jurkat T cells were observed in primary mouse T cells isolated from Rap1E63-Tg mice and Rap1-KO mice, respectively. To investigate whether the LFA-1 integrin α and/or β chain had an active role in the enhanced TGF-β-mediated signaling in the presence of Rap1-GTP, we used Rap1E63 Jurkat T cells in which RapL or RIAM were depleted by shRNA (Rap1E63/RapL-KD and Rap1E63/RIAM-KD) because these adaptors selectively regulate the LFA-1 α and the LFA-1 β chain, respectively, downstream of Rap1-GTP. Although in Rap1E63/RapL-KD cells the enhanced TGF-β-induced Smad3 phosphorylation remained unaffected, in Rap1E63/RIAM-KD cells the enhanced TGF-β-induced Smad3 phosphorylation was abrogated. To investigate the biological relevance of these observations, we used T cells from Rap1E63-Tg mice crossed with mice deficient for the LFA-1 α chain. TGF-β resulted in enhanced Smad3 phosphorylation in T cells from Rap1E63-Tg/LFA1-a KO mice similarly to T cells from Rap1E63-Tg mice, indicating that this effect was not dependent on the activation of LFA-1 α chain. In contrast, T cells from RIAMflox/flox -Lck-Cre mice, in which activation of the LFA-1 β chain is impaired, displayed abrogated activation of Smad3 in response to TGF-β. Our data reveal a novel mechanism by which Rap1 regulates T cell responses via outside-in integrin signaling and may have important implications on TGF-β-mediated T cell homeostasis, differentiation and immune quiescence. Disclosures No relevant conflicts of interest to declare.