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1
Nakamura, N., J. Tanaka et K. Sobue. « Rous sarcoma virus-transformed cells develop peculiar adhesive structures along the cell periphery ». Journal of Cell Science 106, no 4 (1 décembre 1993) : 1057–69. http://dx.doi.org/10.1242/jcs.106.4.1057.
Texte intégralRésumé :
Alteration of the cell/substratum adhesive structures of rat fibroblasts (3Y1 cells) upon transformation by Rous sarcoma virus (RSV) was investigated by immunofluorescence microscopy. In serum-containing culture medium, 3Y1 cells developed focal adhesions as their main adhesive structures, while BY1 cells expressed peculiar close contacts along the cell periphery with the vitronectin receptor integrin, in addition to podosomes. These peripheral close contacts are referred to as the peripheral adhesions. The peripheral adhesions were observed as a darker region than podosomes by interference reflection microscopy. They were more easily destroyed by incubating the cells with RGD-containing peptide than were the focal adhesions. In contrast to focal adhesions and podosomes, actin bundles were not detected within the peripheral adhesions, where pp60v-src and tyrosine-phosphorylated proteins accumulated. Expression of the integrin was determined by the substratum composition when BY1 cells were cultured in serum-free culture medium. Under such conditions, BY1 cells expressed the peripheral adhesions within 3 hours on adhesion molecule-coated glass. On the other hand, in serum-containing medium, they first developed focal adhesions transiently at their early stage of adhesion, and then the peripheral adhesions were predominantly expressed within 12 hours. Podosomes were formed in a time course similar to that of the peripheral adhesions. These findings suggest that the peripheral adhesion is a class of stable adhesive structure distinct from the focal adhesion or podosome of BY1 cells. Similar close contact-type peripheral adhesions with the integrin were also observed in a variety of cultured cells such as normal fibroblasts at their logarithmic growth phase, phorbol ester-treated fibroblasts, and several malignant tumor cells, with poorly organized focal adhesions and stress fibers. These findings further suggest that the peripheral adhesions may be widely involved in the adhesion of cells that inadequately develop stress fibers and focal adhesions.
2
Lipke, Peter N., Jason M. Rauceo et Albertus Viljoen. « Cell–Cell Mating Interactions : Overview and Potential of Single-Cell Force Spectroscopy ». International Journal of Molecular Sciences 23, no 3 (20 janvier 2022) : 1110. http://dx.doi.org/10.3390/ijms23031110.
Texte intégralRésumé :
It is an understatement that mating and DNA transfer are key events for living organisms. Among the traits needed to facilitate mating, cell adhesion between gametes is a universal requirement. Thus, there should be specific properties for the adhesion proteins involved in mating. Biochemical and biophysical studies have revealed structural information about mating adhesins, as well as their specificities and affinities, leading to some ideas about these specialized adhesion proteins. Recently, single-cell force spectroscopy (SCFS) has added important findings. In SCFS, mating cells are brought into contact in an atomic force microscope (AFM), and the adhesive forces are monitored through the course of mating. The results have shown some remarkable characteristics of mating adhesins and add knowledge about the design and evolution of mating adhesins.
3
Katoh, Kazuo. « FAK-Dependent Cell Motility and Cell Elongation ». Cells 9, no 1 (12 janvier 2020) : 192. http://dx.doi.org/10.3390/cells9010192.
Texte intégralRésumé :
Fibroblastic cells show specific substrate selectivity for typical cell–substrate adhesion. However, focal adhesion kinase (FAK) contributes to controlling the regulation of orientation and polarity. When fibroblasts attach to micropatterns, tyrosine-phosphorylated proteins and FAK are both detected along the inner border between the adhesive micropatterns and the nonadhesive glass surface. FAK likely plays important roles in regulation of cell adhesion to the substrate, as FAK is a tyrosine-phosphorylated protein that acts as a signal transduction molecule at sites of cell–substrate attachment, called focal adhesions. FAK has been suggested to play a role in the attachment of cells at adhesive micropatterns by affecting cell polarity. Therefore, the localization of FAK might play a key role in recognition of the border of the cell with the adhesive micropattern, thus regulating cell polarity and the cell axis. This review discusses the regulation and molecular mechanism of cell proliferation and cell elongation by FAK and its associated signal transduction proteins.
4
Ventre, Maurizio, Carlo Fortunato Natale, Carmela Rianna et Paolo Antonio Netti. « Topographic cell instructive patterns to control cell adhesion, polarization and migration ». Journal of The Royal Society Interface 11, no 100 (6 novembre 2014) : 20140687. http://dx.doi.org/10.1098/rsif.2014.0687.
Texte intégralRésumé :
Topographic patterns are known to affect cellular processes such as adhesion, migration and differentiation. However, the optimal way to deliver topographic signals to provide cells with precise instructions has not been defined yet. In this work, we hypothesize that topographic patterns may be able to control the sensing and adhesion machinery of cells when their interval features are tuned on the characteristic lengths of filopodial probing and focal adhesions (FAs). Features separated by distance beyond the length of filopodia cannot be readily perceived; therefore, the formation of new adhesions is discouraged. If, however, topographic features are separated by a distance within the reach of filopodia extension, cells can establish contact between adjacent topographic islands. In the latter case, cell adhesion and polarization rely upon the growth of FAs occurring on a specific length scale that depends on the chemical properties of the surface. Topographic patterns and chemical properties may interfere with the growth of FAs, thus making adhesions unstable. To test this hypothesis, we fabricated different micropatterned surfaces displaying feature dimensions and adhesive properties able to interfere with the filopodial sensing and the adhesion maturation, selectively. Our data demonstrate that it is possible to exert a potent control on cell adhesion, elongation and migration by tuning topographic features’ dimensions and surface chemistry.
5
Young, Katherine A., Laura Biggins et Hayley J. Sharpe. « Protein tyrosine phosphatases in cell adhesion ». Biochemical Journal 478, no 5 (10 mars 2021) : 1061–83. http://dx.doi.org/10.1042/bcj20200511.
Texte intégralRésumé :
Adhesive structures between cells and with the surrounding matrix are essential for the development of multicellular organisms. In addition to providing mechanical integrity, they are key signalling centres providing feedback on the extracellular environment to the cell interior, and vice versa. During development, mitosis and repair, cell adhesions must undergo extensive remodelling. Post-translational modifications of proteins within these complexes serve as switches for activity. Tyrosine phosphorylation is an important modification in cell adhesion that is dynamically regulated by the protein tyrosine phosphatases (PTPs) and protein tyrosine kinases. Several PTPs are implicated in the assembly and maintenance of cell adhesions, however, their signalling functions remain poorly defined. The PTPs can act by directly dephosphorylating adhesive complex components or function as scaffolds. In this review, we will focus on human PTPs and discuss their individual roles in major adhesion complexes, as well as Hippo signalling. We have collated PTP interactome and cell adhesome datasets, which reveal extensive connections between PTPs and cell adhesions that are relatively unexplored. Finally, we reflect on the dysregulation of PTPs and cell adhesions in disease.
6
Simmons, David L. « Dissecting the modes of interactions amongst cell adhesion molecules ». Development 119, Supplement (1 décembre 1993) : 193–203. http://dx.doi.org/10.1242/dev.119.supplement.193.
Texte intégralRésumé :
The process of cell adhesion can be mediated by more than SO molecules. Fortunately, most of these can be grouped into a small number of super families. For example, more than half of all leukocyte adhesion molecules are members of the immunoglobulin super-family. The principles of cell-cell adhesion are reviewed including: kinetics and equilibria; on/off rates; affinities/avidities; homotypic/heterotypic interactions; mapping and delineation of binding sites. These principles are illustrated with two CAMs: firstly the interaction of the homotypic epithelial/myeloid adhesins CD66, and the endothelial adhesin, CD31, and secondly the heterotypic adhesins ICAM-1, 2 and 3, which interact with the leukocyte integrin LFA-1.
7
Lotz, M. M., C. A. Burdsal, H. P. Erickson et D. R. McClay. « Cell adhesion to fibronectin and tenascin : quantitative measurements of initial binding and subsequent strengthening response. » Journal of Cell Biology 109, no 4 (1 octobre 1989) : 1795–805. http://dx.doi.org/10.1083/jcb.109.4.1795.
Texte intégralRésumé :
Cell-substratum adhesion strengths have been quantified using fibroblasts and glioma cells binding to two extracellular matrix proteins, fibronectin and tenascin. A centrifugal force-based adhesion assay was used for the adhesive strength measurements, and the corresponding morphology of the adhesions was visualized by interference reflection microscopy. The initial adhesions as measured at 4 degrees C were on the order of 10(-5)dynes/cell and did not involve the cytoskeleton. Adhesion to fibronectin after 15 min at 37 degrees C were more than an order of magnitude stronger; the strengthening response required cytoskeletal involvement. By contrast to the marked strengthening of adhesion to FN, adhesion to TN was unchanged or weakened after 15 min at 37 degrees C. The absolute strength of adhesion achieved varied according to protein and cell type. When a mixed substratum of fibronectin and tenascin was tested, the presence of tenascin was found to reduce the level of the strengthening of cell adhesion normally observed at 37 degrees C on a substratum of fibronectin alone. Parallel analysis of corresponding interference reflection micrographs showed that differences in the area of cell surface within 10-15 nm of the substratum correlated closely with each of the changes in adhesion observed: after incubation for 15 min on fibronectin at 37 degrees C, glioma cells increased their surface area within close contact to the substrate by integral to 125-fold. Cells on tenascin did not increase their surface area of contact. The increased surface area of contact and the inhibitory activity of cytochalasin b suggest that the adhesive "strengthening" in the 15 min after initial binding brings additional adhesion molecules into the adhesive site and couples the actin cytoskeleton to the adhesion complex.
8
Mentzer, S. J., D. V. Faller et S. J. Burakoff. « Interferon-gamma induction of LFA-1-mediated homotypic adhesion of human monocytes. » Journal of Immunology 137, no 1 (1 juillet 1986) : 108–13. http://dx.doi.org/10.4049/jimmunol.137.1.108.
Texte intégralRésumé :
Abstract Cell-cell adhesion plays an important role in monocyte function. To investigate the molecular basis for monocyte adhesion, we used recombinant interferon-gamma to induce the formation of homotypic monocyte adhesions. The induction of homotypic adhesions correlated with the increased expression of the LFA-1 membrane molecule. LFA-1 surface expression was increased twofold, whereas expression levels of other monocyte surface molecules including CR3 and p150,95 were unchanged. The direct involvement of LFA-1 in monocyte adhesion was addressed by anti-LFA-1 monoclonal antibody inhibition of homotypic adhesions. Two monoclonal antibodies to distinct epitopes on the LFA-1 alpha-chain completely inhibited homotypic adhesions. Antibodies to a variety of other monocyte surface molecules, often present at higher cell surface density than LFA-1, did not inhibit homotypic adhesion. A panel of monoclonal antibodies that recognized different functional epitopes on the LFA-1 alpha-chain inhibited homotypic monocyte in a hierarchy identical to that observed in previous studies of cell-mediated cytotoxicity. These findings suggest that LFA-1 serves an adhesive function for human mononuclear phagocytes. In addition to providing a molecular basis for homotypic monocyte adhesions, the results suggest a more general role for LFA-1 in monocyte adhesion reactions.
9
Willaert, Ronnie G., Yeseren Kayacan et Bart Devreese. « The Flo Adhesin Family ». Pathogens 10, no 11 (28 octobre 2021) : 1397. http://dx.doi.org/10.3390/pathogens10111397.
Texte intégralRésumé :
The first step in the infection of fungal pathogens in humans is the adhesion of the pathogen to host tissue cells or abiotic surfaces such as catheters and implants. One of the main players involved in this are the expressed cell wall adhesins. Here, we review the Flo adhesin family and their involvement in the adhesion of these yeasts during human infections. Firstly, we redefined the Flo adhesin family based on the domain architectures that are present in the Flo adhesins and their functions, and set up a new classification of Flo adhesins. Next, the structure, function, and adhesion mechanisms of the Flo adhesins whose structure has been solved are discussed in detail. Finally, we identified from Pfam database datamining yeasts that could express Flo adhesins and are encountered in human infections and their adhesin architectures. These yeasts are discussed in relation to their adhesion characteristics and involvement in infections.
10
Murphy-Ullrich, J. E., et M. Höök. « Thrombospondin modulates focal adhesions in endothelial cells. » Journal of Cell Biology 109, no 3 (1 septembre 1989) : 1309–19. http://dx.doi.org/10.1083/jcb.109.3.1309.
Texte intégralRésumé :
We examined the effects of thrombospondin (TSP) in the substrate adhesion of bovine aortic endothelial cells. The protein was tested both as a substrate for cell adhesion and as a modulator of the later stages of the cell adhesive process. TSP substrates supported the attachment of some BAE cells, but not cell spreading or the formation of focal adhesion plaques. In contrast, cells seeded on fibrinogen or fibronectin substrates were able to complete the adhesive process, as indicated by the formation of focal adhesion plaques. Incubation of cells in suspension with soluble TSP before or at the time of seeding onto fibronectin substrates resulted in an inhibition of focal adhesion formation. Furthermore, the addition of TSP to fully adherent cells in situ or prespread on fibronectin substrates caused a reduction in the number of cells, which were positive for focal adhesions, although there was no significant effect on cell spreading. In a dose-dependent manner, TSP reduced the number of cells with adhesion plaques to approximately 60% of control levels. The distribution of remaining adhesion plaques in TSP-treated cells was also altered: plaques were primarily limited to the periphery of cells and were not present in the central cell body, as in control cells treated with BSA. The observed effects were specific for TSP and were not observed with platelet factor 4, beta-thromboglobulin, or fibronectin. The TSP-mediated loss of adhesion plaques was neutralized by the addition of heparin, fucoidan, other heparin-binding proteins, and by a monoclonal antibody to the heparin binding domain of TSP, but not by antibodies to the core or carboxy-terminal regions of TSP. The interaction of the heparin-binding domain of TSP with cell-associated heparan sulfate appears to be an important mechanistic component for this activity of TSP. These data indicate that TSP may have a role in destabilizing cell adhesion through prevention of focal adhesion formation and by loss of preformed focal adhesions.
11
Bach, Cuc T. T., Sarah Creed, Jessie Zhong, Maha Mahmassani, Galina Schevzov, Justine Stehn, Lauren N. Cowell et al. « Tropomyosin Isoform Expression Regulates the Transition of Adhesions To Determine Cell Speed and Direction ». Molecular and Cellular Biology 29, no 6 (5 janvier 2009) : 1506–14. http://dx.doi.org/10.1128/mcb.00857-08.
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ABSTRACT The balance of transition between distinct adhesion types contributes to the regulation of mesenchymal cell migration, and the characteristic association of adhesions with actin filaments led us to question the role of actin filament-associating proteins in the transition between adhesive states. Tropomyosin isoform association with actin filaments imparts distinct filament structures, and we have thus investigated the role for tropomyosins in determining the formation of distinct adhesion structures. Using combinations of overexpression, knockdown, and knockout approaches, we establish that Tm5NM1 preferentially stabilizes focal adhesions and drives the transition to fibrillar adhesions via stabilization of actin filaments. Moreover, our data suggest that the expression of Tm5NM1 is a critical determinant of paxillin phosphorylation, a signaling event that is necessary for focal adhesion disassembly. Thus, we propose that Tm5NM1 can regulate the feedback loop between focal adhesion disassembly and focal complex formation at the leading edge that is required for productive and directed cell movement.
12
Ayalon, O., H. Sabanai, M. G. Lampugnani, E. Dejana et B. Geiger. « Spatial and temporal relationships between cadherins and PECAM-1 in cell-cell junctions of human endothelial cells. » Journal of Cell Biology 126, no 1 (1 juillet 1994) : 247–58. http://dx.doi.org/10.1083/jcb.126.1.247.
Texte intégralRésumé :
The integrity of the endothelial layer, which lines the entire cavity of the vascular system, depends on tight adhesion of the cells to the underlying basement membrane as well as to each other. It has been previously shown that such interactions occur via membrane receptors that determine the specificity, topology, and mechanical properties of the surface adhesion. Cell-cell junctions between endothelial cells, in culture and in situ, involve both Ca(2+)-dependent and -independent mechanisms that are mediated by distinct adhesion molecules. Ca(2+)-dependent cell-cell adhesion occurs mostly via members of the cadherin family, which locally anchor the microfilament system to the plasma membrane, in adherens junctions. Ca(2+)-independent adhesions were reported to mainly involve members of the Ig superfamily. In this study, we performed three-dimensional microscopic analysis of the relative subcellular distributions of these two endothelial intercellular adhesion systems. We show that cadherins are located at adjacent (usually more apical), yet clearly distinct domains of the lateral plasma membrane, compared to PECAM-1. Moreover, cadherins were first organized in adherens junctions within 2 h after seeding of endothelial cells, forming multiple lateral patches which developed into an extensive belt-like structure over a period of 24 h. PECAM-1 became associated with surface adhesions significantly later and became progressively associated with the cadherin-containing adhesions. Cadherins and PECAM-1 also differed in their detergent extractability, reflecting differences in their mode of association with the cytoskeleton. Moreover, the two adhesion systems could be differentially modulated since short treatment with the Ca2+ chelator EGTA, disrupted the cadherin junctions leaving PECAM-1 apparently intact. These results confirm that endothelial cells possess distinct intercellular contact mechanisms that differ in their spatial and temporal organization as well as in their functional properties.
13
Garrod, David, et Tomomi E. Kimura. « Hyper-adhesion : a new concept in cell–cell adhesion ». Biochemical Society Transactions 36, no 2 (20 mars 2008) : 195–201. http://dx.doi.org/10.1042/bst0360195.
Texte intégralRésumé :
We have developed a new concept of cell–cell adhesion termed ‘hyper-adhesion’, the very strong adhesion adopted by desmosomes. This uniquely desmosomal property accounts for their ability to provide the intercellular links in the desmosome–intermediate filament complex. These links are targeted by diseases, resulting in disruption of the complex with severe consequences. Hyper-adhesion is characteristic of desmosomes in tissues and is believed to result from a highly ordered arrangement of the extracellular domains of the desmosomal cadherins that locks their binding interaction so that it is highly resistant to disruption. This ordered arrangement may be reflected by and dependent upon a similarly ordered molecular structure of the desmosomal plaque. Hyper-adhesion can be down-regulated to a more weakly adhesive state by cell signalling involving protein kinase C, which translocates to the desmosomal plaque. Down-regulation takes place in wound edge epithelium and appears to be accompanied by loss of the ordered arrangement causing desmosomes to adopt the type of weaker adhesion characteristic of adherens junctions. We review the evidence for hyper-adhesion and speculate on the molecular basis of its mechanism.
14
Hall, Jeffrey W., Bruno P. Lima, Gaetan G. Herbomel, Tata Gopinath, LeAnna McDonald, Michael T. Shyne, John K. Lee et al. « An intramembrane sensory circuit monitors sortase A–mediated processing of streptococcal adhesins ». Science Signaling 12, no 580 (7 mai 2019) : eaas9941. http://dx.doi.org/10.1126/scisignal.aas9941.
Texte intégralRésumé :
Bacterial adhesins mediate adhesion to substrates and biofilm formation. Adhesins of the LPXTG family are posttranslationally processed by the cell membrane–localized peptidase sortase A, which cleaves the LPXTG motif. This generates a short C-terminal peptide (C-pep) that remains in the cell membrane, whereas the mature adhesin is incorporated into the cell wall. Genes encoding adhesins of the oral bacteriumStreptococcus gordoniiwere differentially expressed depending on whether the bacteria were isolated from saliva or dental plaque and appeared to be coordinately regulated. Deletion ofsspAandsspB (sspAB), both of which encode LPXTG-containing adhesins, unexpectedly enhanced adhesion and biofilm formation. C-peps produced from a model LPXTG-containing adhesin localized to the cell membrane and bound to and inhibited the intramembrane sensor histidine kinase SGO_1180, thus preventing activation of the cognate response regulator SGO_1181. The absence of SspAB C-peps induced the expression of thescaCBAoperon encoding the lipoprotein adhesin ScaA, which was sufficient to preserve and even enhance biofilm formation. This C-pep–driven regulatory circuit also exists in pathogenic streptococci and is likely conserved among Gram-positive bacteria. This quality control mechanism ensures that the bacteria can form biofilms under diverse environmental conditions and may play a role in optimizing adhesion and biofilm formation.
15
Tozluoglu, Melda, Yanlan Mao, Paul A. Bates et Erik Sahai. « Cost–benefit analysis of the mechanisms that enable migrating cells to sustain motility upon changes in matrix environments ». Journal of The Royal Society Interface 12, no 106 (mai 2015) : 20141355. http://dx.doi.org/10.1098/rsif.2014.1355.
Texte intégralRésumé :
Cells can move through extracellular environments with varying geometries and adhesive properties. Adaptation to these differences is achieved by switching between different modes of motility, including lamellipod-driven and blebbing motility. Further, cells can modulate their level of adhesion to the extracellular matrix (ECM) depending on both the level of force applied to the adhesions and cell intrinsic biochemical properties. We have constructed a computational model of cell motility to investigate how motile cells transition between extracellular environments with varying surface continuity, confinement and adhesion. Changes in migration strategy are an emergent property of cells as the ECM geometry and adhesion changes. The transition into confined environments with discontinuous ECM fibres is sufficient to induce shifts from lamellipod-based to blebbing motility, while changes in confinement alone within a continuous geometry are not. The geometry of the ECM facilitates plasticity, by inducing shifts where the cell has high marginal gain from a mode change, and conserving persistency where the cell can continue movement regardless of the motility mode. This regulation of cell motility is independent of global changes in cytoskeletal properties, but requires locally higher linkage between the actin network and the plasma membrane at the cell rear, and changes in internal cell pressure. In addition to matrix geometry, we consider how cells might transition between ECM of different adhesiveness. We find that this requires positive feedback between the forces cells apply on the adhesion points, and the strength of the cell–ECM adhesions on those sites. This positive feedback leads to the emergence of a small number of highly adhesive cores, similar to focal adhesions. While the range of ECM adhesion levels the cell can invade is expanded with this feedback mechanism; the velocities are lowered for conditions where the positive feedback is not vital. Thus, plasticity of cell motility sacrifices the benefits of specialization, for robustness.
16
Greenwood, Jeffrey A., Anne B. Theibert, Glenn D. Prestwich et Joanne E. Murphy-Ullrich. « Restructuring of Focal Adhesion Plaques by Pi 3-Kinase ». Journal of Cell Biology 150, no 3 (7 août 2000) : 627–42. http://dx.doi.org/10.1083/jcb.150.3.627.
Texte intégralRésumé :
Focal adhesions are an elaborate network of interconnecting proteins linking actin stress fibers to the extracellular matrix substrate. Modulation of the focal adhesion plaque provides a mechanism for the regulation of cellular adhesive strength. Using interference reflection microscopy, we found that activation of phosphoinositide 3-kinase (PI 3-kinase) by PDGF induces the dissipation of focal adhesions. Loss of this close apposition between the cell membrane and the extracellular matrix coincided with a redistribution of α-actinin and vinculin from the focal adhesion complex to the Triton X-100–soluble fraction. In contrast, talin and paxillin remained localized to focal adhesions, suggesting that activation of PI 3-kinase induced a restructuring of the plaque rather than complete dispersion. Furthermore, phosphatidylinositol (3,4,5)-trisphosphate (PtdIns (3,4,5)-P3), a lipid product of PI 3-kinase, was sufficient to induce restructuring of the focal adhesion plaque. We also found that PtdIns (3,4,5)-P3 binds to α-actinin in PDGF-treated cells. Further evidence demonstrated that activation of PI 3-kinase by PDGF induced a decrease in the association of α-actinin with the integrin β subunit, and that PtdIns (3,4,5)-P3 could disrupt this interaction in vitro. Modification of focal adhesion structure by PI 3-kinase and its lipid product, PtdIns (3,4,5)-P3, has important implications for the regulation of cellular adhesive strength and motility.
17
van Steijn, Leonie, Inge M. N. Wortel, Clément Sire, Loïc Dupré, Guy Theraulaz et Roeland M. H. Merks. « Computational modelling of cell motility modes emerging from cell-matrix adhesion dynamics ». PLOS Computational Biology 18, no 2 (14 février 2022) : e1009156. http://dx.doi.org/10.1371/journal.pcbi.1009156.
Texte intégralRésumé :
Lymphocytes have been described to perform different motility patterns such as Brownian random walks, persistent random walks, and Lévy walks. Depending on the conditions, such as confinement or the distribution of target cells, either Brownian or Lévy walks lead to more efficient interaction with the targets. The diversity of these motility patterns may be explained by an adaptive response to the surrounding extracellular matrix (ECM). Indeed, depending on the ECM composition, lymphocytes either display a floating motility without attaching to the ECM, or sliding and stepping motility with respectively continuous or discontinuous attachment to the ECM, or pivoting behaviour with sustained attachment to the ECM. Moreover, on the long term, lymphocytes either perform a persistent random walk or a Brownian-like movement depending on the ECM composition. How the ECM affects cell motility is still incompletely understood. Here, we integrate essential mechanistic details of the lymphocyte-matrix adhesions and lymphocyte intrinsic cytoskeletal induced cell propulsion into a Cellular Potts model (CPM). We show that the combination of de novo cell-matrix adhesion formation, adhesion growth and shrinkage, adhesion rupture, and feedback of adhesions onto cell propulsion recapitulates multiple lymphocyte behaviours, for different lymphocyte subsets and various substrates. With an increasing attachment area and increased adhesion strength, the cells’ speed and persistence decreases. Additionally, the model predicts random walks with short-term persistent but long-term subdiffusive properties resulting in a pivoting type of motility. For small adhesion areas, the spatial distribution of adhesions emerges as a key factor influencing cell motility. Small adhesions at the front allow for more persistent motility than larger clusters at the back, despite a similar total adhesion area. In conclusion, we present an integrated framework to simulate the effects of ECM proteins on cell-matrix adhesion dynamics. The model reveals a sufficient set of principles explaining the plasticity of lymphocyte motility.
18
Kirov, S. M., L. J. Hayward et M. A. Nerrie. « Adhesion ofAeromonassp. to cell lines used as models for intestinal adhesion ». Epidemiology and Infection 115, no 3 (décembre 1995) : 465–73. http://dx.doi.org/10.1017/s0950268800058623.
Texte intégralRésumé :
SummaryAdhesion to HEp-2 cells has been shown to correlate with enteropathogenicity forAeromonasspecies. Such adhesion is thought to reflect the ability of strains to adhere to human intestinal enterocytes, although HEp-2 cells are not of intestinal origin. In this study strains ofAeromonas veroniibiotype sobria isolated from various sources were investigated in parallel assays for their ability to adhere to HEp-2 cells and to an intestinal cell line (Caco-2). Quantitative assays showed identical adhesion values were obtained with both cell lines. Adhesion was best when bacteria were grown at 22 °C compared with 37 °C and 7 °C. Some environmental isolates showed greater adhesion when grown at 7 °C than when grown at 37 °C. Filamentous structures on these strains are also optimally expressed under the above conditions (reported elsewhere). Mechanical shearing or trypsin treatment to remove surface structures from several adhesive strains grown at 22 °C decreased adhesion to cell lines by 50–80% providing further indirect evidence that filamentous adhesins may play a role in cell adhesion for thisAeromonasspecies.
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Banisadr, Afsheen, Mariam Eick, Pranjali Beri, Alison D. Parisian, Benjamin Yeoman, Jesse K. Placone, Adam J. Engler et Frank Furnari. « EGFRvIII uses intrinsic and extrinsic mechanisms to reduce glioma adhesion and increase migration ». Journal of Cell Science 133, no 24 (26 novembre 2020) : jcs247189. http://dx.doi.org/10.1242/jcs.247189.
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ABSTRACTA lack of biological markers has limited our ability to identify the invasive cells responsible for glioblastoma multiforme (GBM). To become migratory and invasive, cells must downregulate matrix adhesions, which could be a physical marker of invasive potential. We engineered murine astrocytes with common GBM mutations, e.g. Ink4a (Ink) or PTEN deletion and expressing a constitutively active EGF receptor truncation (EGFRvIII), to elucidate their effect on adhesion. While loss of Ink or PTEN did not affect adhesion, counterparts expressing EGFRvIII were significantly less adhesive. EGFRvIII reduced focal adhesion size and number, and these cells – with more labile adhesions – displayed enhanced migration. Regulation appears to depend not on physical receptor association to integrins but, rather, on the activity of the receptor kinase, resulting in transcriptional integrin repression. Interestingly, EGFRvIII intrinsic signals can be propagated by cytokine crosstalk to cells expressing wild-type EGFR, resulting in reduced adhesion and enhanced migration. These data identify potential intrinsic and extrinsic mechanisms that gliomas use to invade surrounding parenchyma.
20
NEWTON, SEAN C., et CLARKE F. MILLETTE. « Sertoli Cell Plasma Membrane Polypeptides Involved in Spermatogenic Cell‐Sertoli Cell Adhesion ». Journal of Andrology 13, no 2 (4 mars 1992) : 160–71. http://dx.doi.org/10.1002/j.1939-4640.1992.tb01651.x.
Texte intégralRésumé :
ABSTRACT: This study concerns Sertoli cell‐spermatogenic cell adhesive interactions in the seminiferous tubule. Sertoli cell surface polypeptides involved in germ cell‐Sertoli cell adhesion were identified by serological inhibition of an in vitro Sertoli‐germ cell adhesion assay. This assay was modified from a previously reported adhesion assay, and employs a scanning laser cytometer for quantification of adherent cells. Reactivity of the polyclonal antiserum raised against rat Sertoli cells was also assessed via immunofluorescent microscopy. The addition of antiserum to the adhesion assay resulted in a 42% to 66% inhibition of cell‐cell adhesion. Moreover, preincubation of antiserum with Sertoli cell monolayers resulted in a significant reduction of spermatogenic cell binding. Conversely, preincubation of antiserum with germ cells resulted in no reduction. Western blot analysis of the antiserum against purified Sertoli cell membranes indicated reactivity with four polypeptides. The data suggest that one or more of these polypeptides are directly involved in the adhesion of germ cells to Sertoli cell monolayers in vitro.
21
Akimov, Sergey S., Dmitry Krylov, Laurie F. Fleischman et Alexey M. Belkin. « Tissue Transglutaminase Is an Integrin-Binding Adhesion Coreceptor for Fibronectin ». Journal of Cell Biology 148, no 4 (21 février 2000) : 825–38. http://dx.doi.org/10.1083/jcb.148.4.825.
Texte intégralRésumé :
The protein cross-linking enzyme tissue transglutaminase binds in vitro with high affinity to fibronectin via its 42-kD gelatin-binding domain. Here we report that cell surface transglutaminase mediates adhesion and spreading of cells on the 42-kD fibronectin fragment, which lacks integrin-binding motifs. Overexpression of tissue transglutaminase increases its amount on the cell surface, enhances adhesion and spreading on fibronectin and its 42-kD fragment, enlarges focal adhesions, and amplifies adhesion-dependent phosphorylation of focal adhesion kinase. These effects are specific for tissue transglutaminase and are not shared by its functional homologue, a catalytic subunit of factor XIII. Adhesive function of tissue transglutaminase does not require its cross-linking activity but depends on its stable noncovalent association with integrins. Transglutaminase interacts directly with multiple integrins of β1 and β3 subfamilies, but not with β2 integrins. Complexes of transglutaminase with integrins are formed inside the cell during biosynthesis and accumulate on the surface and in focal adhesions. Together our results demonstrate that tissue transglutaminase mediates the interaction of integrins with fibronectin, thereby acting as an integrin-associated coreceptor to promote cell adhesion and spreading.
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Andreozzi, Elisa, et Gaylen A. Uhlich. « PchE Regulation of Escherichia coli O157:H7 Flagella, Controlling the Transition to Host Cell Attachment ». International Journal of Molecular Sciences 21, no 13 (28 juin 2020) : 4592. http://dx.doi.org/10.3390/ijms21134592.
Texte intégralRésumé :
Shiga toxins and intimate adhesion controlled by the locus of enterocyte effacement are major enterohemorrhagic Escherichia coli (EHEC) virulence factors. Curli fimbriae also contribute to cell adhesion and are essential biofilm components. The transcriptional regulator PchE represses the expression of curli and their adhesion to HEp-2 cells. Past studies indicate that pchE also represses additional adhesins that contribute to HEp-2 cell attachment. In this study, we tested for pchE regulation of several tissue adhesins and their regulators. Three adhesin-encoding genes (eae, lpfA1, fliC) and four master regulators (csgD, stpA, ler, flhDC) were controlled by pchE. pchE over-expression strongly up-regulated fliC but the marked flagella induction reduced the attachment of O157:H7 clinical isolate PA20 to HEp-2 cells, indicating that flagella were blocking cell attachments rather than functioning as an adhesin. Chemotaxis, motor, structural, and regulatory genes in the flagellar operons were all increased by pchE expression, as was PA20 motility. This study identifies new members in the pchE regulon and shows that pchE stimulates flagellar motility while repressing cell adhesion, likely to support EHEC movement to the intestinal surface early in infection. However, induced or inappropriate pchE-dependent flagellar expression could block cell attachments later during disease progression.
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Goodwin, Katharine, Emily E. Lostchuck, Kaitlyn M. L. Cramb, Teresa Zulueta-Coarasa, Rodrigo Fernandez-Gonzalez et Guy Tanentzapf. « Cell–cell and cell–extracellular matrix adhesions cooperate to organize actomyosin networks and maintain force transmission during dorsal closure ». Molecular Biology of the Cell 28, no 10 (15 mai 2017) : 1301–10. http://dx.doi.org/10.1091/mbc.e17-01-0033.
Texte intégralRésumé :
Tissue morphogenesis relies on the coordinated action of actin networks, cell–cell adhesions, and cell–extracellular matrix (ECM) adhesions. Such coordination can be achieved through cross-talk between cell–cell and cell–ECM adhesions. Drosophila dorsal closure (DC), a morphogenetic process in which an extraembryonic tissue called the amnioserosa contracts and ingresses to close a discontinuity in the dorsal epidermis of the embryo, requires both cell–cell and cell–ECM adhesions. However, whether the functions of these two types of adhesions are coordinated during DC is not known. Here we analyzed possible interdependence between cell–cell and cell–ECM adhesions during DC and its effect on the actomyosin network. We find that loss of cell–ECM adhesion results in aberrant distributions of cadherin-mediated adhesions and actin networks in the amnioserosa and subsequent disruption of myosin recruitment and dynamics. Moreover, loss of cell–cell adhesion caused up-regulation of cell–ECM adhesion, leading to reduced cell deformation and force transmission across amnioserosa cells. Our results show how interdependence between cell–cell and cell–ECM adhesions is important in regulating cell behaviors, force generation, and force transmission critical for tissue morphogenesis.
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Douglas, L. Julia. « Adhesin - receptor interactions in the attachment ofCandida albicansto host epithelial cells ». Canadian Journal of Botany 73, S1 (31 décembre 1995) : 1147–53. http://dx.doi.org/10.1139/b95-371.
Texte intégralRésumé :
The ability of Candida albicans to adhere to a variety of host surfaces is thought to be an important factor in the pathogenesis of candidosis. Adhesion of the yeast form of the fungus to epithelial cells can involve several kinds of adhesion – receptor interaction. Yeast adhesins are typically mannoproteins associated with fibrils or fimbriae on the fungal surface. Lectinlike interactions have been identified between the protein portion of two mannoprotein adhesins and glycosides containing L-fucose or N-acetylglucosamine. The fucoside-binding adhesin has been purified and shown to have an affinity for glycosphingolipid receptors carrying the H blood-group antigen. A fimbrial adhesin has also been described that binds to gangliosides containing a βGalNAc(1–4)βGal disaccharide sequence. Other mannoprotein adhesins proposed recently include the factor 6 epitope present on serotype A strains of C. albicans and an integrin analogue. Adhesin expression appears to be regulated by a number of environmental signals, including osmolarity and the availability of iron and sugars. Additional adhesion-dependent signals might trigger further responses such as the initiation of morphogenesis. Key words: Candida albicans, yeast adhesion, epithelial cell adhesion.
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Hillery, Cheryl A., J. Paul Scott et Ming C. Du. « The Carboxy-Terminal Cell-Binding Domain of Thrombospondin Is Essential for Sickle Red Blood Cell Adhesion ». Blood 94, no 1 (1 juillet 1999) : 302–9. http://dx.doi.org/10.1182/blood.v94.1.302.413k38_302_309.
Texte intégralRésumé :
Sickle red blood cells (SS-RBCs) have enhanced adhesion to the plasma and subendothelial matrix protein thrombospondin-1 (TSP) under conditions of flow in vitro. TSP has at least four domains that mediate cell adhesion. The goal of this study was to map the site(s) on TSP that binds SS-RBCs. Purified TSP proteolytic fragments containing either the N-terminal heparin-binding domain, or the type 1, 2, or 3 repeats, failed to sustain SS-RBC adhesion (<10% adhesion). However, a 140-kD thermolysin TSP fragment, containing the carboxy-terminal cell-binding domain in addition to the type 1, 2, and 3 repeats fully supported the adhesion of SS-RBCs (126% ± 25% adhesion). Two cell-binding domain adhesive peptides, 4N1K (KRFYVVMWKK) and 7N3 (FIRVVMYEGKK), failed to either inhibit or support SS-RBC adhesion to TSP. In addition, monoclonal antibody C6.7, which blocks platelet and melanoma cell adhesion to the cell-binding domain, did not inhibit SS-RBC adhesion to TSP. These data suggest that a novel adhesive site within the cell binding domain of TSP promotes the adhesion of sickle RBCs to TSP. Furthermore, soluble TSP did not bind SS-RBCs as detected by flow cytometry, nor inhibit SS-RBC adhesion to immobilized TSP under conditions of flow, indicating that the adhesive site on TSP that recognizes SS-RBCs is exposed only after TSP binds to a matrix. We conclude that the intact carboxy-terminal cell-binding domain of TSP is essential for the adhesion of sickle RBCs under flow conditions. This study also provides evidence for a unique adhesive site within the cell-binding domain that is exposed after TSP binds to a matrix.
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Bialer, Magalí G., Gabriela Sycz, Florencia Muñoz González, Mariana C. Ferrero, Pablo C. Baldi et Angeles Zorreguieta. « Adhesins of Brucella : Their Roles in the Interaction with the Host ». Pathogens 9, no 11 (12 novembre 2020) : 942. http://dx.doi.org/10.3390/pathogens9110942.
Texte intégralRésumé :
A central aspect of Brucella pathogenicity is its ability to invade, survive, and replicate in diverse phagocytic and non-phagocytic cell types, leading to chronic infections and chronic inflammatory phenomena. Adhesion to the target cell is a critical first step in the invasion process. Several Brucella adhesins have been shown to mediate adhesion to cells, extracellular matrix components (ECM), or both. These include the sialic acid-binding proteins SP29 and SP41 (binding to erythrocytes and epithelial cells, respectively), the BigA and BigB proteins that contain an Ig-like domain (binding to cell adhesion molecules in epithelial cells), the monomeric autotransporters BmaA, BmaB, and BmaC (binding to ECM components, epithelial cells, osteoblasts, synoviocytes, and trophoblasts), the trimeric autotransporters BtaE and BtaF (binding to ECM components and epithelial cells) and Bp26 (binding to ECM components). An in vivo role has also been shown for the trimeric autotransporters, as deletion mutants display decreased colonization after oral and/or respiratory infection in mice, and it has also been suggested for BigA and BigB. Several adhesins have shown unipolar localization, suggesting that Brucella would express an adhesive pole. Adhesin-based vaccines may be useful to prevent brucellosis, as intranasal immunization in mice with BtaF conferred high levels of protection against oral challenge with B. suis.
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Behrens, J., M. M. Mareel, F. M. Van Roy et W. Birchmeier. « Dissecting tumor cell invasion : epithelial cells acquire invasive properties after the loss of uvomorulin-mediated cell-cell adhesion. » Journal of Cell Biology 108, no 6 (1 juin 1989) : 2435–47. http://dx.doi.org/10.1083/jcb.108.6.2435.
Texte intégralRésumé :
The generation of invasiveness in transformed cells represents an essential step of tumor progression. We show here, first, that nontransformed Madin-Darby canine kidney (MDCK) epithelial cells acquire invasive properties when intercellular adhesion is specifically inhibited by the addition of antibodies against the cell adhesion molecule uvomorulin; the separated cells then invade collagen gels and embryonal heart tissue. Second, MDCK cells transformed with Harvey and Moloney sarcoma viruses are constitutively invasive, and they were found not to express uvomorulin at their cell surface. These data suggest that the loss of adhesive function of uvomorulin (which is identical to E-cadherin and homologous to L-CAM) is a critical step in the promotion of epithelial cells to a more malignant, i.e., invasive, phenotype. Similar modulation of intercellular adhesion might also occur during invasion of carcinoma cells in vivo.
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Alberici Delsin, Lara Elis, Cédric Plutoni, Anna Clouvel, Sarah Keil, Léa Marpeaux, Lina Elouassouli, Adele Khavari, Allen J. Ehrlicher et Gregory Emery. « MAP4K4 regulates forces at cell–cell and cell–matrix adhesions to promote collective cell migration ». Life Science Alliance 6, no 9 (27 juin 2023) : e202302196. http://dx.doi.org/10.26508/lsa.202302196.
Texte intégralRésumé :
Collective cell migration is not only important for development and tissue homeostasis but can also promote cancer metastasis. To migrate collectively, cells need to coordinate cellular extensions and retractions, adhesion sites dynamics, and forces generation and transmission. Nevertheless, the regulatory mechanisms coordinating these processes remain elusive. Using A431 carcinoma cells, we identify the kinase MAP4K4 as a central regulator of collective migration. We show that MAP4K4 inactivation blocks the migration of clusters, whereas its overexpression decreases cluster cohesion. MAP4K4 regulates protrusion and retraction dynamics, remodels the actomyosin cytoskeleton, and controls the stability of both cell–cell and cell–substrate adhesion. MAP4K4 promotes focal adhesion disassembly through the phosphorylation of the actin and plasma membrane crosslinker moesin but disassembles adherens junctions through a moesin-independent mechanism. By analyzing traction and intercellular forces, we found that MAP4K4 loss of function leads to a tensional disequilibrium throughout the cell cluster, increasing the traction forces and the tension loading at the cell–cell adhesions. Together, our results indicate that MAP4K4 activity is a key regulator of biomechanical forces at adhesion sites, promoting collective migration.
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Murphy-Ullrich, J. E., M. A. Pallero, N. Boerth, J. A. Greenwood, T. M. Lincoln et T. L. Cornwell. « Cyclic GMP-dependent protein kinase is required for thrombospondin and tenascin mediated focal adhesion disassembly ». Journal of Cell Science 109, no 10 (1 octobre 1996) : 2499–508. http://dx.doi.org/10.1242/jcs.109.10.2499.
Texte intégralRésumé :
Focal adhesions are specialized regions of cell membranes that are foci for the transmission of signals between the outside and the inside of the cell. Intracellular signaling events are important in the organization and stability of these structures. In previous work, we showed that the counter-adhesive extracellular matrix proteins, thrombospondin, tenascin, and SPARC, induce the disassembly of focal adhesion plaques and we identified the active regions of these proteins. In order to determine the mechanisms whereby the anti-adhesive matrix proteins modulate cytoskeletal organization and focal adhesion integrity, we examined the role of protein kinases in mediating the loss of focal adhesions by these proteins. Data from these studies show that cGMP-dependent protein kinase is necessary to mediate focal adhesion disassembly triggered by either thrombospondin or tenascin, but not by SPARC. In experiments using various protein kinase inhibitors, we observed that selective inhibitors of cyclic GMP-dependent protein kinase, KT5823 and Rp-8-Br-cGMPS, blocked the effects of both the active sequence of thrombospondin 1 (hep I) and the alternatively-spliced segment (TNfnA-D) of tenascin-C on focal adhesion disassembly. Moreover, early passage rat aortic smooth muscle cells which have high levels of cGMP-dependent protein kinase were sensitive to hep I treatment, in contrast to passaged cGMP-dependent protein kinase deficient cells which were refractory to hep I or TNfnA-D treatment, but were sensitive to SPARC. Transfection of passaged smooth muscle cells with the catalytic domain of PKG I alpha restored responsiveness to hep I and TNfnA-D. While these studies show that cGMP-dependent protein kinase activity is necessary for thrombospondin and tenascin-mediated focal adhesion disassembly, kinase activity alone is not sufficient to induce disassembly as transfection of the catalytic domain of the kinase in the absence of additional stimuli does not result in loss of focal adhesions.
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CHAPLAIN, MARK A. J., MIROSŁAW LACHOWICZ, ZUZANNA SZYMAŃSKA et DARIUSZ WRZOSEK. « MATHEMATICAL MODELLING OF CANCER INVASION : THE IMPORTANCE OF CELL–CELL ADHESION AND CELL–MATRIX ADHESION ». Mathematical Models and Methods in Applied Sciences 21, no 04 (avril 2011) : 719–43. http://dx.doi.org/10.1142/s0218202511005192.
Texte intégralRésumé :
The process of invasion of tissue by cancer cells is crucial for metastasis — the formation of secondary tumours — which is the main cause of mortality in patients with cancer. In the invasion process itself, adhesion, both cell–cell and cell–matrix, plays an extremely important role. In this paper, a mathematical model of cancer cell invasion of the extracellular matrix is developed by incorporating cell–cell adhesion as well as cell–matrix adhesion into the model. Considering the interactions between cancer cells, extracellular matrix and matrix degrading enzymes, the model consists of a system of reaction–diffusion partial integro–differential equations, with nonlocal (integral) terms describing the adhesive interactions between cancer cells and the host tissue, i.e. cell–cell adhesion and cell–matrix adhesion. Having formulated the model, we prove the existence and uniqueness of global in time classical solutions which are uniformly bounded. Then, using computational simulations, we investigate the effects of the relative importance of cell–cell adhesion and cell–matrix adhesion on the invasion process. In particular, we examine the roles of cell–cell adhesion and cell–matrix adhesion in generating heterogeneous spatio-temporal solutions. Finally, in the discussion section, concluding remarks are made and open problems are indicated.
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Canalli, Andreia A., Carla F. Franco-Penteado, Fabiola Traina, Nicola Conran, Rafael Morgante, Sheley Gambero, Sara T. O. Saad et Fernando F. Costa. « Altered Red Cell and Platelet Adhesion in the Hemolytic Diseases : Hereditary Spherocytosis, Paroxysmal Nocturnal Hemoglobinuria and Sickle Cell Anemia. » Blood 108, no 11 (16 novembre 2006) : 1238. http://dx.doi.org/10.1182/blood.v108.11.1238.1238.
Texte intégralRésumé :
Abstract Increasing evidence exists to suggest that intravascular hemolysis may have important pathophysiological consequences resulting from reduced vascular nitric oxide (NO) bioavailability due to hemoglobin-mediated NO scavenging; such consequences may include endothelial dysfunction and vasculopathy. Hemolytic diseases such as hereditary spherocytosis (HS), paroxysmal nocturnal hemoglobinuria (PNH) and sickle cell anemia (SCA), despite having diverse etiologies, share a number of complications that include pulmonary and systolic arterial hypertension, cutaneous leg ulcerations and, in PNH and SCA, thrombosis and possibly stroke. Since reduced vascular NO bioavailability may affect cellular adhesion molecule function, we sought to compare the adhesive properties of red cells and platelets in these diseases. Blood samples were collected from healthy control subjects and from patients with HS (non-splenectomized), PNH (with hemolysis) or SCA (in steady state and not on hydroxyurea therapy); all patients presented reticulocytosis. Red blood cells (RBC) and platelets were washed and resuspended in RPMI medium (RBC) or Krebs solution (platelets). RBC suspensions were then allowed to adhere to fibronectin (FN)-coated plates (20mg/ml) and platelets to fibrinogen (FB)-coated plates (50mg/ml), employing previously standardized static adhesion assays. Cell adhesion was expressed as the percentage of cells adhered. RBC adhesion to FN was slightly, but significantly, increased for cells from HS and PNH patients compared to control RBC (13.8±1.1 %, n=7, P<0.05; 13.7±0.8 %, n=6, P<0.05 for HS and PNH, respectively, compared to 10.5±0.7 % of cells adhered, n=7 for control; Mann-Whitney Test). SCA RBC adhesion to FN, however, was markedly increased when compared to control RBC adhesion (25.7±4.6 %, n=9, P<0.01). With regard to platelet adhesion, HS platelets did not demonstrate any significant alteration in adhesion to FB (14.78±2.91 % compared to 10.94±1.31 % for HS and control, respectively; n=10 and 11, P>0.05). In contrast, PNH and SCA platelet adhesions were significantly increased (23.1±4.7 %, n=8, P<0.05 and 29.5±6.1 %, n=6, P<0.001 for HPN and SCA, respectively). Interestingly, whilst control platelet adhesion was much lower than hemolytic disease platelet adhesion, co-incubation of platelets with a thrombin stimulus (100 U/ml) significantly increased the adhesion of control platelets only (241.2±21.0 %, n=10, P<0.002; Wilcoxon Matched-Pairs test), indicating that hemolytic disease platelets appear to be in an already activated state. Significant alterations in platelet adhesive properties were seen, therefore, in PNH and SCA, but not HS. Such alterations may contribute to the pathophysiology of these diseases, particularly in thrombotic events. Marked alterations in RBC adhesion were, however, seen only in SCA. Thus, whilst hemolysis is common to HS, PNH and SCA, we found cell adhesive functions to vary between diseases. Although it is possible that the rate of intravascular hemolysis is greater in SCA than HS, it is unlikely that the rate of SCA intravascular hemolysis is much greater than that occurring in PNH, where the bulk of hemolysis occurs intravascularly. Thus, the markedly increased cellular adhesive properties observed in SCA appear not to be mediated by hemolysis alone, but probably involve the participation of other mechanisms peculiar to the disease.
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Powner, Dale, Petra M. Kopp, Susan J. Monkley, David R. Critchley et Fedor Berditchevski. « Tetraspanin CD9 in cell migration ». Biochemical Society Transactions 39, no 2 (22 mars 2011) : 563–67. http://dx.doi.org/10.1042/bst0390563.
Texte intégralRésumé :
Tetraspanin CD9 is associated with integrin adhesion receptors and it was reported that CD9 regulates integrin-dependent cell migration and invasion. Pro- and anti-migratory effects of CD9 have been linked to adhesion-dependent signalling pathways, including phosphorylation of FAK (focal adhesion kinase) and activation of phosphoinositide 3-kinase, p38 MAPK (mitogen-activated protein kinase) and JNK (c-Jun N-terminal kinase). In the present paper, we describe a novel mechanism whereby CD9 specifically controls localization of talin1, one of the critical regulators of integrin activation, to focal adhesions: CD9-deficiency leads to impaired localization of talin1 to focal adhesions and correlates with increased motility of breast cancer cells.
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Aguilar-Cuenca, Rocio, Clara Llorente-Gonzalez, Carlos Vicente et Miguel Vicente-Manzanares. « Microfilament-coordinated adhesion dynamics drives single cell migration and shapes whole tissues ». F1000Research 6 (17 février 2017) : 160. http://dx.doi.org/10.12688/f1000research.10356.1.
Texte intégralRésumé :
Cell adhesion to the substratum and/or other cells is a crucial step of cell migration. While essential in the case of solitary migrating cells (for example, immune cells), it becomes particularly important in collective cell migration, in which cells maintain contact with their neighbors while moving directionally. Adhesive coordination is paramount in physiological contexts (for example, during organogenesis) but also in pathology (for example, tumor metastasis). In this review, we address the need for a coordinated regulation of cell-cell and cell-matrix adhesions during collective cell migration. We emphasize the role of the actin cytoskeleton as an intracellular integrator of cadherin- and integrin-based adhesions and the emerging role of mechanics in the maintenance, reinforcement, and turnover of adhesive contacts. Recent advances in understanding the mechanical regulation of several components of cadherin and integrin adhesions allow us to revisit the adhesive clutch hypothesis that controls the degree of adhesive engagement during protrusion. Finally, we provide a brief overview of the major impact of these discoveries when using more physiological three-dimensional models of single and collective cell migration.
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Westhoff, M. A., B. Serrels, V. J. Fincham, M. C. Frame et N. O. Carragher. « Src-Mediated Phosphorylation of Focal Adhesion Kinase Couples Actin and Adhesion Dynamics to Survival Signaling ». Molecular and Cellular Biology 24, no 18 (15 septembre 2004) : 8113–33. http://dx.doi.org/10.1128/mcb.24.18.8113-8133.2004.
Texte intégralRésumé :
ABSTRACT Integrin-associated focal adhesions not only provide adhesive links between cellular actin and extracellular matrix but also are sites of signal transmission into the cell interior. Many cell responses signal through focal adhesion kinase (FAK), often by integrin-induced autophosphorylation of FAK or phosphorylation by Src family kinases. Here, we used an interfering FAK mutant (4-9F-FAK) to show that Src-dependent FAK phosphorylation is required for focal adhesion turnover and cell migration, by controlling assembly of a calpain 2/FAK/Src/p42ERK complex, calpain activation, and proteolysis of FAK. Expression of 4-9F-FAK in FAK-deficient fibroblasts also disrupts F-actin assembly associated with normal adhesion and spreading. In addition, we found that FAK's ability to regulate both assembly and disassembly of the actin and adhesion networks may be linked to regulation of the protease calpain. Surprisingly, we also found that the same interfering 4-9F-FAK mutant protein causes apoptosis of serum-deprived, transformed cells and suppresses anchorage-independent growth. These data show that Src-mediated phosphorylation of FAK acts as a pivotal regulator of both actin and adhesion dynamics and survival signaling, which, in turn, control apparently distinct processes such as cell migration and anchorage-independent growth. This also highlights that dynamic regulation of actin and adhesions (which include the integrin matrix receptors) is critical to signaling output and biological responses.
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Blackstone, B. N., R. Li, W. E. Ackerman, S. N. Ghadiali, H. M. Powell et D. A. Kniss. « Myoferlin depletion elevates focal adhesion kinase and paxillin phosphorylation and enhances cell-matrix adhesion in breast cancer cells ». American Journal of Physiology-Cell Physiology 308, no 8 (15 avril 2015) : C642—C649. http://dx.doi.org/10.1152/ajpcell.00276.2014.
Texte intégralRésumé :
Breast cancer is the second leading cause of malignant death among women. A crucial feature of metastatic cancers is their propensity to lose adhesion to the underlying basement membrane as they transition to a motile phenotype and invade surrounding tissue. Attachment to the extracellular matrix is mediated by a complex of adhesion proteins, including integrins, signaling molecules, actin and actin-binding proteins, and scaffolding proteins. Focal adhesion kinase (FAK) is pivotal for the organization of focal contacts and maturation into focal adhesions, and disruption of this process is a hallmark of early cancer invasive potential. Our recent work has revealed that myoferlin (MYOF) mediates breast tumor cell motility and invasive phenotype. In this study we demonstrate that noninvasive breast cancer cell lines exhibit increased cell-substrate adhesion and that silencing of MYOF using RNAi in the highly invasive human breast cancer cell line MDA-MB-231 also enhances cell-substrate adhesion. In addition, we detected elevated tyrosine phosphorylation of FAK (FAKY397) and paxillin (PAXY118), markers of focal adhesion protein activation. Morphometric analysis of PAX expression revealed that RNAi-mediated depletion of MYOF resulted in larger, more elongated focal adhesions, in contrast to cells transduced with a control virus (MDA-231LVC cells), which exhibited smaller focal contacts. Finally, MYOF silencing in MDA-MB-231 cells exhibited a more elaborate ventral cytoskeletal structure near focal adhesions, typified by pronounced actin stress fibers. These data support the hypothesis that MYOF regulates cell adhesions and cell-substrate adhesion strength and may account for the high degree of motility in invasive breast cancer cells.
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Oakes, Patrick W., Yvonne Beckham, Jonathan Stricker et Margaret L. Gardel. « Tension is required but not sufficient for focal adhesion maturation without a stress fiber template ». Journal of Cell Biology 196, no 3 (30 janvier 2012) : 363–74. http://dx.doi.org/10.1083/jcb.201107042.
Texte intégralRésumé :
Focal adhesion composition and size are modulated in a myosin II–dependent maturation process that controls adhesion, migration, and matrix remodeling. As myosin II activity drives stress fiber assembly and enhanced tension at adhesions simultaneously, the extent to which adhesion maturation is driven by tension or altered actin architecture is unknown. We show that perturbations to formin and α-actinin 1 activity selectively inhibited stress fiber assembly at adhesions but retained a contractile lamella that generated large tension on adhesions. Despite relatively unperturbed adhesion dynamics and force transmission, impaired stress fiber assembly impeded focal adhesion compositional maturation and fibronectin remodeling. Finally, we show that compositional maturation of focal adhesions could occur even when myosin II–dependent cellular tension was reduced by 80%. We propose that stress fiber assembly at the adhesion site serves as a structural template that facilitates adhesion maturation over a wide range of tensions. This work identifies the essential role of lamellar actin architecture in adhesion maturation.
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Longley, R. L., A. Woods, A. Fleetwood, G. J. Cowling, J. T. Gallagher et J. R. Couchman. « Control of morphology, cytoskeleton and migration by syndecan-4 ». Journal of Cell Science 112, no 20 (15 octobre 1999) : 3421–31. http://dx.doi.org/10.1242/jcs.112.20.3421.
Texte intégralRésumé :
Syndecan-4 is a widely expressed transmembrane heparan sulfate proteoglycan which localizes to focal adhesions. Previous studies showed that the syndecan-4 cytoplasmic domain can associate with and potentiate the activity of protein kinase C, which is required for focal adhesion formation. To examine further the role of syndecan-4 in cell adhesion, we expressed syndecan-4 cDNA constructs in CHO-K1 cells. Syndecan-2 transfection was used to confirm effects seen were specific for syndecan-4. Cells overexpressing full length syndecan-4 core protein exhibited a more flattened, fibroblastic morphology, with increased focal adhesion formation and decreased cell motility. Expression of a syndecan-4 core protein with either a partial or complete deletion of the cytoplasmic domain or of an antisense construct led to markedly decreased spreading and focal adhesion formation, a more epithelioid morphology, and decreased motility. Overexpression of syndecan-2 changed the adhesive phenotype, but did not markedly alter focal adhesion and microfilament bundle formation. The data suggest that syndecan-4 is a regulator of focal adhesion and stress fiber formation, and influences both morphology and migration.
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Revach, Or-Yam, Inna Grosheva et Benjamin Geiger. « Biomechanical regulation of focal adhesion and invadopodia formation ». Journal of Cell Science 133, no 20 (15 octobre 2020) : jcs244848. http://dx.doi.org/10.1242/jcs.244848.
Texte intégralRésumé :
ABSTRACTIntegrin adhesions are a structurally and functionally diverse family of transmembrane, multi-protein complexes that link the intracellular cytoskeleton to the extracellular matrix (ECM). The different members of this family, including focal adhesions (FAs), focal complexes, fibrillar adhesions, podosomes and invadopodia, contain many shared scaffolding and signaling ‘adhesome’ components, as well as distinct molecules that perform specific functions, unique to each adhesion form. In this Hypothesis, we address the pivotal roles of mechanical forces, generated by local actin polymerization or actomyosin-based contractility, in the formation, maturation and functionality of two members of the integrin adhesions family, namely FAs and invadopodia, which display distinct structures and functional properties. FAs are robust and stable ECM contacts, associated with contractile stress fibers, while invadopodia are invasive adhesions that degrade the underlying matrix and penetrate into it. We discuss here the mechanisms, whereby these two types of adhesion utilize a similar molecular machinery to drive very different – often opposing cellular activities, and hypothesize that early stages of FAs and invadopodia assembly use similar biomechanical principles, whereas maturation of the two structures, and their ‘adhesive’ and ‘invasive’ functionalities require distinct sources of biomechanical reinforcement.
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Labbate, Maurizio, Hua Zhu, Leena Thung, Rani Bandara, Martin R. Larsen, Mark D. P. Willcox, Michael Givskov, Scott A. Rice et Staffan Kjelleberg. « Quorum-Sensing Regulation of Adhesion in Serratia marcescens MG1 Is Surface Dependent ». Journal of Bacteriology 189, no 7 (19 janvier 2007) : 2702–11. http://dx.doi.org/10.1128/jb.01582-06.
Texte intégralRésumé :
ABSTRACT Serratia marcescens is an opportunistic pathogen and a major cause of ocular infections. In previous studies of S. marcescens MG1, we showed that biofilm maturation and sloughing were regulated by N-acyl homoserine lactone (AHL)-based quorum sensing (QS). Because of the importance of adhesion in initiating biofilm formation and infection, the primary goal of this study was to determine whether QS is important in adhesion to both abiotic and biotic surfaces, as assessed by determining the degree of attachment to hydrophilic tissue culture plates and human corneal epithelial (HCE) cells. Our results demonstrate that while adhesion to the abiotic surface was AHL regulated, adhesion to the HCE cell biotic surface was not. Type I fimbriae were identified as the critical adhesin for non-QS-mediated attachment to the biotic HCE cell surface but played no role in adhesion to the abiotic surface. While we were not able to identify a single QS-regulated adhesin essential for attachment to the abiotic surface, four AHL-regulated genes involved in adhesion to the abiotic surface were identified. Interestingly, two of these genes, bsmA and bsmB, were also shown to be involved in adhesion to the biotic surface in a non-QS-controlled fashion. Therefore, the expression of these two genes appears to be cocontrolled by regulators other than the QS system for mediation of attachment to HCE cells. We also found that QS in S. marcescens regulates other potential cell surface adhesins, including exopolysaccharide and the outer membrane protein OmpX. We concluded that S. marcescens MG1 utilizes different regulatory systems and adhesins in attachment to biotic and abiotic surfaces and that QS is a main regulatory pathway in adhesion to an abiotic surface but not in adhesion to a biotic surface.
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Aoshiba, K., S. I. Rennard et J. R. Spurzem. « Cell-matrix and cell-cell interactions modulate apoptosis of bronchial epithelial cells ». American Journal of Physiology-Lung Cellular and Molecular Physiology 272, no 1 (1 janvier 1997) : L28—L37. http://dx.doi.org/10.1152/ajplung.1997.272.1.l28.
Texte intégralRésumé :
Apoptosis is an important process maintaining cell number and tissue structure. To determine whether cell-extracellular matrix (ECM) and cell-cell interactions modulate apoptosis in bronchial epithelium, we cultured human bronchial epithelial cells in different conditions and evaluated the cells for apoptosis. We found that plating cells in conditions that prevent cell-ECM adhesion induced apoptosis. Plating cells on type I collagen, fibronectin, and biosynthesized matrix prevented apoptosis, due at least in part to integrin-mediated adhesion. When cells were cultured at high density but under conditions preventing cell-substratum adhesion, aggregation occurred. Apoptosis was inversely correlated with aggregation. Cell-cell adhesion in these conditions was mediated at least partly by integrins containing alpha v. Cell aggregation was not associated with activation of a signaling pathway that is usually activated by cell-ECM adhesion, phosphorylation of focal adhesion kinase, but was associated with Bcl-2 protein expression, consistent with the concept that Bcl-2 protects against apoptosis. We conclude that both cell-ECM and cell-cell interactions, likely mediated in part by integrins, modulate apoptosis in bronchial epithelium.
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Gilmore, A. P., et L. H. Romer. « Inhibition of focal adhesion kinase (FAK) signaling in focal adhesions decreases cell motility and proliferation. » Molecular Biology of the Cell 7, no 8 (août 1996) : 1209–24. http://dx.doi.org/10.1091/mbc.7.8.1209.
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It has been proposed that the focal adhesion kinase (FAK) mediates focal adhesion formation through tyrosine phosphorylation during cell adhesion. We investigated the role of FAK in focal adhesion structure and function. Loading cells with a glutathione-S-transferase fusion protein (GST-Cterm) containing the FAK focal adhesion targeting sequence, but not the kinase domain, decreased the association of endogenous FAK with focal adhesions. This displacement of endogenous FAK in both BALB/c 3T3 cells and human umbilical vein endothelial cells loaded with GST-Cterm decreased focal adhesion phosphotyrosine content. Neither cell type, however, exhibited a reduction in focal adhesions after GST-Cterm loading. These results indicate that FAK mediates adhesion-associated tyrosine phosphorylation, but not the formation of focal adhesions. We then examined the effect of inhibiting FAK function on other adhesion-dependent cell behavior. Cells microinjected with GST-Cterm exhibited decreased migration. In addition, cells injected with GST-Cterm had decreased DNA synthesis compared with control-injected or noninjected cells. These findings suggest that FAK functions in the regulation of cell migration and cell proliferation.
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Usatyuk, Peter V., et Viswanathan Natarajan. « Regulation of reactive oxygen species-induced endothelial cell-cell and cell-matrix contacts by focal adhesion kinase and adherens junction proteins ». American Journal of Physiology-Lung Cellular and Molecular Physiology 289, no 6 (décembre 2005) : L999—L1010. http://dx.doi.org/10.1152/ajplung.00211.2005.
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Oxidants, generated by activated neutrophils, have been implicated in the pathophysiology of vascular disorders and lung injury; however, mechanisms of oxidant-mediated endothelial barrier dysfunction are unclear. Here, we have investigated the role of focal adhesion kinase (FAK) in regulating hydrogen peroxide (H2O2)-mediated tyrosine phosphorylation of intercellular adhesion proteins and barrier function in endothelium. Treatment of bovine pulmonary artery endothelial cells (BPAECs) with H2O2 increased tyrosine phosphorylation of FAK, paxillin, β-catenin, and vascular endothelial (VE)-cadherin and decreased transendothelial electrical resistance (TER), an index of cell-cell adhesion and/or cell-matrix adhesion. To study the role of FAK in H2O2-induced TER changes, BPAECs were transfected with vector or FAK wild-type or FAK-related non-kinase (FRNK) plasmids. Overexpression of FRNK reduced FAK expression and attenuated H2O2-mediated tyrosine phosphorylation of FAK, paxillin, β-catenin, and VE-cadherin and cell-cell adhesion. Additionally, FRNK prevented H2O2-induced distribution of FAK, paxillin, β-catenin, or VE-cadherin toward focal adhesions and cell-cell adhesions but not actin stress fiber formation. These results suggest that activation of FAK by H2O2 is an important event in oxidant-mediated VE barrier function regulated by cell-cell and cell-matrix contacts.
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Gallant, Nathan D., Kristin E. Michael et Andrés J. García. « Cell Adhesion Strengthening : Contributions of Adhesive Area, Integrin Binding, and Focal Adhesion Assembly ». Molecular Biology of the Cell 16, no 9 (septembre 2005) : 4329–40. http://dx.doi.org/10.1091/mbc.e05-02-0170.
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Mechanical interactions between a cell and its environment regulate migration, contractility, gene expression, and cell fate. We integrated micropatterned substrates to engineer adhesive area and a hydrodynamic assay to analyze fibroblast adhesion strengthening on fibronectin. Independently of cell spreading, integrin binding and focal adhesion assembly resulted in rapid sevenfold increases in adhesion strength to steady-state levels. Adhesive area strongly modulated adhesion strength, integrin binding, and vinculin and talin recruitment, exhibiting linear increases for small areas. However, above a threshold area, adhesion strength and focal adhesion assembly reached a saturation limit, whereas integrin binding transitioned from a uniform distribution to discrete complexes. Adhesion strength exhibited exponential increases with bound integrin numbers as well as vinculin and talin recruitment, and the relationship between adhesion strength and these biochemical events was accurately described by a simple mechanical model. Furthermore, adhesion strength was regulated by the position of an adhesive patch, comprised of bound integrins and cytoskeletal elements, which generated a constant 200-nN adhesive force. Unexpectedly, focal adhesion assembly, in particular vinculin recruitment, contributed only 30% of the adhesion strength. This work elucidates the roles of adhesive complex size and position in the generation of cell-extracellular matrix forces.
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Hanein, D., H. Sabanay, L. Addadi et B. Geiger. « Selective interactions of cells with crystal surfaces. Implications for the mechanism of cell adhesion ». Journal of Cell Science 104, no 2 (1 février 1993) : 275–88. http://dx.doi.org/10.1242/jcs.104.2.275.
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In this study we have characterized the mode of cell adhesion to calcite and calcium (R,R)-tartrate tetrahydrate crystals. The use of crystals as adhesion substrata was motivated by their well-established chemical nature and structurally defined surfaces. We show that calcite binds A6 Xenopus laevis epithelial cells rapidly and efficiently, most likely via surface-adsorbed proteins. Surface topology had only a limited effect on the adhesive interactions. Calcium (R,R)-tartrate tetrahydrate crystals exhibits two chemically equivalent, yet structurally distinct faces that differ mainly in the surface distribution of their lattice water molecules and charges. However, despite the gross similarity between the two faces striking differences were noted in their adhesive behavior. One of the faces was highly adhesive for cells, leading to protein-independent attachment and spreading followed by cell death. In contrast, cell adhesion to the other surface of tartrate was slow (> 24 h) and apparently mediated by RGD-containing protein(s). It was further shown that the latter face of tartrate crystals could be “conditioned” by long (24 h) incubation with serum-containing medium, after which it becomes highly adhesive. The results presented here indicate that crystal surfaces may serve as excellent, structurally defined, substrata for cell adhesion, that cell binding may occur directly or via RGD-containing proteins and that cell adhesion may be dramatically modulated by variations in surface structure. The implications of the results to the mechanism of cell-substratum adhesion are discussed.
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Nybo, Kristie. « Cell Adhesion ». BioTechniques 51, no 4 (octobre 2011) : 235–37. http://dx.doi.org/10.2144/000113747.
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Goridis, C. « Cell adhesion ». Research in Immunology 141, no 7 (janvier 1990) : 796–98. http://dx.doi.org/10.1016/0923-2494(90)90010-v.
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Fleming, Stewart. « Cell adhesion ». Journal of Pathology 170, no 2 (juin 1993) : 205–9. http://dx.doi.org/10.1002/path.1711700217.
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Hiscox, S., et W. G. Jiang. « Ezrin regulates cell-cell and cell-matrix adhesion, a possible role with E-cadherin/beta-catenin ». Journal of Cell Science 112, no 18 (15 septembre 1999) : 3081–90. http://dx.doi.org/10.1242/jcs.112.18.3081.
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Ezrin, radixin, moesin and merlin form a subfamily of conserved proteins in the band 4.1 superfamily. The function of these proteins is to link the plasma membrane to the actin cytoskeleton. Merlin is defective or absent in schwannomas and meningiomas and has been suggested to function as a tumour suppressor. In this study, we have examined the role of ezrin as a potential regulator of the adhesive and invasive behaviour of tumour cells. We have shown that following inhibition of ezrin expression in colo-rectal cancer cells using antisense oligonucleotides, these cells displayed a reduced cell-cell adhesiveness together with a gain in their motile and invasive behaviour. These cells also displayed increased spreading over matrix-coated surfaces. Immunofluorescence studies revealed that antisense-treated cells also displayed an increased staining of paxillin in areas representing focal adhesions. Furthermore, coprecipitation studies revealed an association of ezrin with E-cadherin and beta-catenin. Induction of the phosphorylation of ezrin by orthovanadate and hepatocyte growth factor/scatter factor resulted in changes similar to those seen with antisense treatment, together with a marked decrease in the association of ezrin with both beta-catenin and E-cadherin. It is concluded that ezrin regulates cell-cell and cell-matrix adhesion, by interacting with cell adhesion molecules E-cadherin and beta-catenin, and may thus play an important role in the control of adhesion and invasiveness of cancer cells.
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Chen, Tsute, Koji Nakayama, Lynn Belliveau et Margaret J. Duncan. « Porphyromonas gingivalis Gingipains and Adhesion to Epithelial Cells ». Infection and Immunity 69, no 5 (1 mai 2001) : 3048–56. http://dx.doi.org/10.1128/iai.69.5.3048-3056.2001.
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ABSTRACT Porphyromonas gingivalis is one of the principal organisms associated with adult periodontitis. Bacterial surface proteins such as fimbriae and gingipain hemagglutinin domains have been implicated as adhesins that actuate colonization of epithelium lining the gingival sulcus. We investigated the genetics of P. gingivalis adhesion to monolayers of epithelial cells using wild-type and gingipain mutant strains. These experiments suggested that arginine-specific gingipain (Rgp) catalytic activity modulated adhesion. From the data obtained with rgp mutants, we constructed a working hypothesis predicting that attachment and detachment of P. gingivalis to epithelial cells were mediated by gingipain adhesin and Rgp catalytic domains, respectively. A membrane-based epithelial cell binding assay, used to locate adhesins in extracellular fractions of wild-type and mutant strains, recognized gingipain peptides as adhesins rather than fimbriae. We developed a capture assay that demonstrated the binding of gingipain adhesin peptides to oral epithelial cells. The adherence of fimbrillin to epithelial cells was detected after heat denaturation of cell fractions. The prediction that Rgp catalytic activities mediated detachment was substantiated when the high level of attachment of anrgp mutant was reduced in the presence of wild-type cell fractions that contained gingipain catalytic activities.
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Wang, Chenlu, Sagar Chowdhury, Meghan Driscoll, Carole A. Parent, S. K. Gupta et Wolfgang Losert. « The interplay of cell–cell and cell–substrate adhesion in collective cell migration ». Journal of The Royal Society Interface 11, no 100 (6 novembre 2014) : 20140684. http://dx.doi.org/10.1098/rsif.2014.0684.
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Collective cell migration often involves notable cell–cell and cell–substrate adhesions and highly coordinated motion of touching cells. We focus on the interplay between cell–substrate adhesion and cell–cell adhesion. We show that the loss of cell-surface contact does not significantly alter the dynamic pattern of protrusions and retractions of fast migrating amoeboid cells ( Dictyostelium discoideum ), but significantly changes their ability to adhere to other cells. Analysis of the dynamics of cell shapes reveals that cells that are adherent to a surface may coordinate their motion with neighbouring cells through protrusion waves that travel across cell–cell contacts. However, while shape waves exist if cells are detached from surfaces, they do not couple cell to cell. In addition, our investigation of actin polymerization indicates that loss of cell-surface adhesion changes actin polymerization at cell–cell contacts. To further investigate cell–cell/cell–substrate interactions, we used optical micromanipulation to form cell–substrate contact at controlled locations. We find that both cell-shape dynamics and cytoskeletal activity respond rapidly to the formation of cell–substrate contact.