Journal articles: 'Actin remodeling proteins'

1

Olave, Ivan A., Samara L. Reck-Peterson, and Gerald R. Crabtree. "Nuclear Actin and Actin-Related Proteins in Chromatin Remodeling." Annual Review of Biochemistry 71, no. 1 (June 2002): 755–81. http://dx.doi.org/10.1146/annurev.biochem.71.110601.135507.

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Galkin, V. E., A. Orlova, D. S. Kudryashov, A. Solodukhin, E. Reisler, G. F. Schroder, and E. H. Egelman. "Remodeling of actin filaments by ADF/cofilin proteins." Proceedings of the National Academy of Sciences 108, no. 51 (December 7, 2011): 20568–72. http://dx.doi.org/10.1073/pnas.1110109108.

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Eitzen, Gary, Li Wang, Naomi Thorngren, and William Wickner. "Remodeling of organelle-bound actin is required for yeast vacuole fusion." Journal of Cell Biology 158, no. 4 (August 12, 2002): 669–79. http://dx.doi.org/10.1083/jcb.200204089.

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Actin participates in several intracellular trafficking pathways. We now find that actin, bound to the surface of purified yeast vacuoles in the absence of cytosol or cytoskeleton, regulates the last compartment mixing stage of homotypic vacuole fusion. The Cdc42p GTPase is known to be required for vacuole fusion. We now show that proteins of the Cdc42p-regulated actin remodeling cascade (Cdc42p → Cla4p → Las17p/Vrp1p → Arp2/3 complex → actin) are enriched on isolated vacuoles. Vacuole fusion is dramatically altered by perturbation of the vacuole-bound actin, either by mutation of the ACT1 gene, addition of specific actin ligands such as latrunculin B or jasplakinolide, antibody to the actin regulatory proteins Las17p (yeast Wiskott-Aldrich syndrome protein) or Arp2/3, or deletion of actin regulatory genes. On docked vacuoles, actin is enriched at the “vertex ring” membrane microdomain where fusion occurs and is required for the terminal steps leading to membrane fusion. This role for actin may extend to other trafficking systems.

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Stolp, Bettina, Libin Abraham, Jochen M. Rudolph, and Oliver T. Fackler. "Lentiviral Nef Proteins Utilize PAK2-Mediated Deregulation of Cofilin as a General Strategy To Interfere with Actin Remodeling." Journal of Virology 84, no. 8 (February 10, 2010): 3935–48. http://dx.doi.org/10.1128/jvi.02467-09.

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ABSTRACT Nef is an accessory protein and pathogenicity factor of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) which elevates virus replication in vivo. We recently described for HIV type 1SF2 (HIV-1SF2) the potent interference of Nef with T-lymphocyte chemotaxis via its association with the cellular kinase PAK2. Mechanistic analysis revealed that this interaction results in deregulation of the actin-severing factor cofilin and thus blocks the chemokine-mediated actin remodeling required for cell motility. However, the efficiency of PAK2 association is highly variable among Nef proteins from different lentiviruses, prompting us to evaluate the conservation of this actin-remodeling/cofilin-deregulating mechanism. Based on the analysis of a total of 17 HIV-1, HIV-2, and SIV Nef proteins, we report here that inhibition of chemokine-induced actin remodeling as well as inactivation of cofilin are strongly conserved activities of lentiviral Nef proteins. Of note, even for Nef variants that display only marginal PAK2 association in vitro, these activities require the integrity of a PAK2 recruitment motif and the presence of endogenous PAK2. Thus, reduced in vitro affinity to PAK2 does not indicate limited functionality of Nef-PAK2 complexes in intact HIV-1 host cells. These results establish hijacking of PAK2 for deregulation of cofilin and inhibition of triggered actin remodeling as a highly conserved function of lentiviral Nef proteins, supporting the notion that PAK2 association may be critical for Nef's activity in vivo.

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Hoffman, Laura M., Christopher C. Jensen, Aashi Chaturvedi, Masaaki Yoshigi, and Mary C. Beckerle. "Stretch-induced actin remodeling requires targeting of zyxin to stress fibers and recruitment of actin regulators." Molecular Biology of the Cell 23, no. 10 (May 15, 2012): 1846–59. http://dx.doi.org/10.1091/mbc.e11-12-1057.

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Reinforcement of actin stress fibers in response to mechanical stimulation depends on a posttranslational mechanism that requires the LIM protein zyxin. The C-terminal LIM region of zyxin directs the force-sensitive accumulation of zyxin on actin stress fibers. The N-terminal region of zyxin promotes actin reinforcement even when Rho kinase is inhibited. The mechanosensitive integrin effector p130Cas binds zyxin but is not required for mitogen-activated protein kinase–dependent zyxin phosphorylation or stress fiber remodeling in cells exposed to uniaxial cyclic stretch. α-Actinin and Ena/VASP proteins bind to the stress fiber reinforcement domain of zyxin. Mutation of their docking sites reveals that zyxin is required for recruitment of both groups of proteins to regions of stress fiber remodeling. Zyxin-null cells reconstituted with zyxin variants that lack either α-actinin or Ena/VASP-binding capacity display compromised response to mechanical stimulation. Our findings define a bipartite mechanism for stretch-induced actin remodeling that involves mechanosensitive targeting of zyxin to actin stress fibers and localized recruitment of actin regulatory machinery.

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Liu, Jing, Xinhua Guo, Narla Mohandas, Joel A. Chasis, and Xiuli An. "Membrane remodeling during reticulocyte maturation." Blood 115, no. 10 (March 11, 2010): 2021–27. http://dx.doi.org/10.1182/blood-2009-08-241182.

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Abstract The transition of reticulocytes into erythrocytes is accompanied by extensive changes in the structure and properties of the plasma membrane. These changes include an increase in shear resistance, loss of surface area, and acquisition of a biconcave shape. The processes by which these changes are effected have remained largely undefined. Here we examine how the expression of 30 distinct membrane proteins and their interactions change during murine reticulocyte maturation. We show that tubulin and cytosolic actin are lost, whereas the membrane content of myosin, tropomyosin, intercellular adhesion molecule-4, glucose transporter-4, Na-K-ATPase, sodium/hydrogen exchanger 1, glycophorin A, CD47, Duffy, and Kell is reduced. The degradation of tubulin and actin is, at least in part, through the ubiquitin-proteasome degradation pathway. In regard to the protein-protein interactions, the formation of membrane-associated spectrin tetramers from dimers is unperturbed, whereas the interactions responsible for the formation of the membrane-skeletal junctions are weaker in reticulocytes, as is the attachment of transmembrane proteins to these structures. This weakness, in part, results from the elevated phosphorylation of 4.1R in reticulocytes, which leads to a decrease in shear resistance by reducing its interaction with spectrin and actin. These observations begin to unravel the mechanistic basis of crucial changes accompanying reticulocyte maturation.

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Goodson, Holly V., and William F. Hawse. "Molecular evolution of the actin family." Journal of Cell Science 115, no. 13 (July 1, 2002): 2619–22. http://dx.doi.org/10.1242/jcs.115.13.2619.

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Members of the actin family have well-characterized cytoskeletal functions,but actin and actin-related proteins (ARPs) have also been implicated in nuclear activities. Previous analyses of the actin family have identified four conserved subfamilies, but many actin-related proteins (ARPs) do not fall into these groups. A new systematic phylogenetic analysis reveals that at least eight ARP subfamilies are conserved from humans to yeast, indicating that these ARPs are part of the core set of eukaryotic proteins. Members of at least three subfamilies appear to be involved in chromatin remodeling,suggesting that ARPs play ancient, fundamental roles in this nuclear process.

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Furman, Craig, Alisha L. Sieminski, Adam V. Kwiatkowski, Douglas A. Rubinson, Eliza Vasile, Roderick T. Bronson, Reinhard Fässler, and Frank B. Gertler. "Ena/VASP is required for endothelial barrier function in vivo." Journal of Cell Biology 179, no. 4 (November 12, 2007): 761–75. http://dx.doi.org/10.1083/jcb.200705002.

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Enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) proteins are key actin regulators that localize at regions of dynamic actin remodeling, including cellular protrusions and cell–cell and cell–matrix junctions. Several studies have suggested that Ena/VASP proteins are involved in the formation and function of cellular junctions. Here, we establish the importance of Ena/VASP in endothelial junctions in vivo by analysis of Ena/VASP-deficient animals. In the absence of Ena/VASP, the vasculature exhibits patterning defects and lacks structural integrity, leading to edema, hemorrhaging, and late stage embryonic lethality. In endothelial cells, we find that Ena/VASP activity is required for normal F-actin content, actomyosin contractility, and proper response to shear stress. These findings demonstrate that Ena/VASP is critical for actin cytoskeleton remodeling events involved in the maintenance of functional endothelia.

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Russo, Ashley J., Alyssa J. Mathiowetz, Steven Hong, Matthew D. Welch, and Kenneth G. Campellone. "Rab1 recruits WHAMM during membrane remodeling but limits actin nucleation." Molecular Biology of the Cell 27, no. 6 (March 15, 2016): 967–78. http://dx.doi.org/10.1091/mbc.e15-07-0508.

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Small G-proteins are key regulatory molecules that activate the actin nucleation machinery to drive cytoskeletal rearrangements during plasma membrane remodeling. However, the ability of small G-proteins to interact with nucleation factors on internal membranes to control trafficking processes has not been well characterized. Here we investigated roles for members of the Rho, Arf, and Rab G-protein families in regulating WASP homologue associated with actin, membranes, and microtubules (WHAMM), an activator of Arp2/3 complex–mediated actin nucleation. We found that Rab1 stimulated the formation and elongation of WHAMM-associated membrane tubules in cells. Active Rab1 recruited WHAMM to dynamic tubulovesicular structures in fibroblasts, and an active prenylated version of Rab1 bound directly to an N-terminal domain of WHAMM in vitro. In contrast to other G-protein–nucleation factor interactions, Rab1 binding inhibited WHAMM-mediated actin assembly. This ability of Rab1 to regulate WHAMM and the Arp2/3 complex represents a distinct strategy for membrane remodeling in which a Rab G-protein recruits the actin nucleation machinery but dampens its activity.

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Offenhäuser, Nina, Alessandro Borgonovo, Andrea Disanza, Pascale Romano, Isabella Ponzanelli, Gioacchin Iannolo, Pier Paolo Di Fiore, and Giorgio Scita. "The eps8 Family of Proteins Links Growth Factor Stimulation to Actin Reorganization Generating Functional Redundancy in the Ras/Rac Pathway." Molecular Biology of the Cell 15, no. 1 (January 2004): 91–98. http://dx.doi.org/10.1091/mbc.e03-06-0427.

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Sos-1, a guanine nucleotide exchange factor (GEF), eps8 and Abi1, two signaling proteins, and the lipid kinase phosphoinositide 3-kinase (PI3-K), assemble in a multimolecular complex required for Rac activation leading to actin cytoskeletal remodeling. Consistently, eps8 –/– fibroblasts fail to form membrane ruffles in response to growth factor stimulation. Surprisingly, eps8 null mice are healthy, fertile, and display no overt phenotype, suggesting the existence of functional redundancy within this pathway. Here, we describe the identification and characterization of a family of eps8-related proteins, comprising three novel gene products, named eps8L1, eps8L2, and eps8L3. Eps8Ls display collinear topology and 27–42% identity to eps8. Similarly to eps8, eps8Ls interact with Abi1 and Sos-1; however, only eps8L1 and eps8L2 activate the Rac-GEF activity of Sos-1, and bind to actin in vivo. Consistently, eps8L1 and eps8L2, but not eps8L3, localize to PDGF-induced, F-actin–rich ruffles and restore receptor tyrosine kinase (RTK)-mediated actin remodeling when expressed in eps8 –/– fibroblasts. Thus, the eps8Ls define a novel family of proteins responsible for functional redundancy in the RTK-activated signaling pathway leading to actin remodeling. Finally, the patterns of expression of eps8 and eps8L2 in mice are remarkably overlapping, thus providing a likely explanation for the lack of overt phenotype in eps8 null mice.

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Huang, Yanping, Erin O. Comiskey, Renell S. Dupree, Shuixing Li, Anthony J. Koleske, and Janis K. Burkhardt. "The c-Abl tyrosine kinase regulates actin remodeling at the immune synapse." Blood 112, no. 1 (July 1, 2008): 111–19. http://dx.doi.org/10.1182/blood-2007-10-118232.

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Abstract Actin dynamics during T-cell activation are controlled by the coordinate action of multiple actin regulatory proteins, functioning downstream of a complex network of kinases and other signaling molecules. The c-Abl nonreceptor tyrosine kinase regulates actin responses in nonhematopoietic cells, but its function in T cells is poorly understood. Using kinase inhibitors, RNAi, and conditional knockout mice, we investigated the role of c-Abl in controlling the T-cell actin response. We find that c-Abl is required for normal actin polymerization and lamellipodial spreading at the immune synapse, and for downstream events leading to efficient interleukin-2 production. c-Abl also plays a key role in signaling chemokine-induced T-cell migration. c-Abl is required for the appropriate function of 2 proteins known to be important for controlling actin responses to T-cell receptor (TCR) engagement, the actin-stabilizing adapter protein HS1, and the Rac1-dependent actin polymerizing protein WAVE2. c-Abl binds to phospho-HS1 via its SH2 domains and is required for full tyrosine phosphorylation of HS1 during T-cell activation. In addition, c-Abl is required for normal localization of WAVE2 to the immune synapse (IS). These studies identify c-Abl as a key player in the signaling cascade, leading to actin reorganization during T-cell activation.

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Scott, Cameron C., Wendy Dobson, Roberto J. Botelho, Natasha Coady-Osberg, Philippe Chavrier, David A. Knecht, Colin Heath, Philip Stahl, and Sergio Grinstein. "Phosphatidylinositol-4,5-bisphosphate hydrolysis directs actin remodeling during phagocytosis." Journal of Cell Biology 169, no. 1 (April 4, 2005): 139–49. http://dx.doi.org/10.1083/jcb.200412162.

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The Rho GTPases play a critical role in initiating actin polymerization during phagocytosis. In contrast, the factors directing the disassembly of F-actin required for fission of the phagocytic vacuole are ill defined. We used fluorescent chimeric proteins to monitor the dynamics of association of actin and active Cdc42 and Rac1 with the forming phagosome. Although actin was found to disappear from the base of the forming phagosome before sealing was complete, Rac1/Cdc42 activity persisted, suggesting that termination of GTPase activity is not the main determinant of actin disassembly. Furthermore, fully internalized phagosomes engineered to associate constitutively with active Rac1 showed little associated F-actin. The disappearance of phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) from the phagosomal membrane closely paralleled the course of actin disassembly. Furthermore, inhibition of PI(4,5)P2 hydrolysis or increased PI(4,5)P2 generation by overexpression of phosphatidylinositol phosphate kinase I prevented the actin disassembly necessary for the completion of phagocytosis. These observations suggest that hydrolysis of PI(4,5)P2 dictates the remodeling of actin necessary for completion of phagocytosis.

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Tamma, Grazia, Giuseppe Procino, Maria Svelto, and Giovanna Valenti. "Hypotonicity causes actin reorganization and recruitment of the actin-binding ERM protein moesin in membrane protrusions in collecting duct principal cells." American Journal of Physiology-Cell Physiology 292, no. 4 (April 2007): C1476—C1484. http://dx.doi.org/10.1152/ajpcell.00375.2006.

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Hypotonicity-induced cell swelling is characterized by a modification in cell architecture associated with actin cytoskeleton remodeling. The ezrin/radixin/moesin (ERM) family proteins are important signal transducers during actin reorganization regulated by the monomeric G proteins of the Rho family. We report here that in collecting duct CD8 cells hypotonicity-induced cell swelling resulted in deep actin reorganization, consisting of loss of stress fibers and formation of F-actin patches in membrane protrusions where the ERM protein moesin was recruited. Cell swelling increased the interaction between actin and moesin and induced the transition of moesin from an oligomeric to a monomeric functional conformation, characterized by both the COOH- and NH2-terminal domains being exposed. In this conformation, which is stabilized by phosphorylation of a conserved threonine in the COOH-terminal domain by PKC or Rho kinase, moesin can bind interacting proteins. Interestingly, hypotonic stress increased the amount of threonine-phosphorylated moesin, which was prevented by the PKC-α inhibitor Gö-6976 (50 nM). In contrast, the Rho kinase inhibitor Y-27632 (1 μM) did not affect the hypotonicity-induced increase in phosphorylated moesin. The present data represent the first evidence that hypotonicity-induced actin remodeling is associated with phosphorylated moesin recruitment at the cell border and interaction with actin.

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Rudolph, Jochen M., Nina Eickel, Claudia Haller, Michael Schindler, and Oliver T. Fackler. "Inhibition of T-Cell Receptor-Induced Actin Remodeling and Relocalization of Lck Are Evolutionarily Conserved Activities of Lentiviral Nef Proteins." Journal of Virology 83, no. 22 (September 2, 2009): 11528–39. http://dx.doi.org/10.1128/jvi.01423-09.

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ABSTRACT Nef, an important pathogenicity factor of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV), elevates virus replication in vivo. Among other activities, Nef affects T-cell receptor (TCR) signaling via several mechanisms. For HIV-1 Nef these include alteration of the organization and function of the immunological synapse (IS) such as relocalization of the Lck kinase, as well as early inhibition of TCR/CD3 complex (TCR-CD3)-mediated actin rearrangements and tyrosine phosphorylation. Although most SIV and HIV-2 Nef alleles (group 2) potently downregulate cell surface TCR-CD3, this activity was lost in the viral lineage that gave rise to HIV-1 and its SIV counterparts (group 1). To address the contribution of TCR-CD3 downregulation to Nef effects on TCR signal initiation, we compared the activities of 18 group 1 and group 2 Nef proteins, as well as SIV Nef mutants with defects in TCR-CD3 downmodulation. We found that alteration of Lck's subcellular localization is largely conserved and occurs independently of actin remodeling inhibition or TCR-CD3 downregulation. Surprisingly, Nef proteins of both groups also strongly reduced TCR-induced actin remodeling and tyrosine phosphorylation on TCR-stimulatory surfaces and TCR-CD3 downmodulation competence by group 2 Nef proteins only slightly elevated these effects. Furthermore, Nef proteins from HIV-1 and SIV reduced conjugation between infected primary human T lymphocytes and Raji B cells and potently prevented F-actin polarization at the IS independently of their ability to downmodulate TCR-CD3. These results establish alterations of early TCR signaling events at the IS, including F-actin remodeling and relocalization of Lck, as evolutionary conserved activities of highly divergent lentiviral Nef proteins.

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von Blume, Julia, Juan M. Duran, Elena Forlanelli, Anne-Marie Alleaume, Mikhail Egorov, Roman Polishchuk, Henrik Molina, and Vivek Malhotra. "Actin remodeling by ADF/cofilin is required for cargo sorting at the trans-Golgi network." Journal of Cell Biology 187, no. 7 (December 21, 2009): 1055–69. http://dx.doi.org/10.1083/jcb.200908040.

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Knockdown of the actin-severing protein actin-depolymerizing factor (ADF)/cofilin inhibited export of an exogenously expressed soluble secretory protein from Golgi membranes in Drosophila melanogaster and mammalian tissue culture cells. A stable isotope labeling by amino acids in cell culture mass spectrometry–based protein profiling revealed that a large number of endogenous secretory proteins in mammalian cells were not secreted upon ADF/cofilin knockdown. Although many secretory proteins were retained, a Golgi-resident protein and a lysosomal hydrolase were aberrantly secreted upon ADF/cofilin knockdown. Overall, our findings indicate that inactivation of ADF/cofilin perturbed the sorting of a subset of both soluble and integral membrane proteins at the trans-Golgi network (TGN). We suggest that ADF/cofilin-dependent actin trimming generates a sorting domain at the TGN, which filters secretory cargo for export, and that uncontrolled growth of this domain causes missorting of proteins. This type of actin-dependent compartmentalization and filtering of secretory cargo at the TGN by ADF/cofilin could explain sorting of proteins that are destined to the cell surface.

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Hoffman, Laura M., Christopher C. Jensen, Susanne Kloeker, C. L. Albert Wang, Masaaki Yoshigi, and Mary C. Beckerle. "Genetic ablation of zyxin causes Mena/VASP mislocalization, increased motility, and deficits in actin remodeling." Journal of Cell Biology 172, no. 5 (February 27, 2006): 771–82. http://dx.doi.org/10.1083/jcb.200512115.

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Focal adhesions are specialized regions of the cell surface where integrin receptors and associated proteins link the extracellular matrix to the actin cytoskeleton. To define the cellular role of the focal adhesion protein zyxin, we characterized the phenotype of fibroblasts in which the zyxin gene was deleted by homologous recombination. Zyxin-null fibroblasts display enhanced integrin-dependent adhesion and are more migratory than wild-type fibroblasts, displaying reduced dependence on extracellular matrix cues. We identified differences in the profiles of 75- and 80-kD tyrosine-phosphorylated proteins in the zyxin-null cells. Tandem array mass spectrometry identified both modified proteins as isoforms of the actomyosin regulator caldesmon, a protein known to influence contractility, stress fiber formation, and motility. Zyxin-null fibroblasts also show deficits in actin stress fiber remodeling and exhibit changes in the molecular composition of focal adhesions, most notably by severely reduced accumulation of Ena/VASP proteins. We postulate that zyxin cooperates with Ena/VASP proteins and caldesmon to influence integrin-dependent cell motility and actin stress fiber remodeling.

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Treanor, Bebhinn, David Depoil, Andreas Bruckbauer, and Facundo D. Batista. "Dynamic cortical actin remodeling by ERM proteins controls BCR microcluster organization and integrity." Journal of Experimental Medicine 208, no. 5 (April 11, 2011): 1055–68. http://dx.doi.org/10.1084/jem.20101125.

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Signaling microclusters are a common feature of lymphocyte activation. However, the mechanisms controlling the size and organization of these discrete structures are poorly understood. The Ezrin-Radixin-Moesin (ERM) proteins, which link plasma membrane proteins with the actin cytoskeleton and regulate the steady-state diffusion dynamics of the B cell receptor (BCR), are transiently dephosphorylated upon antigen receptor stimulation. In this study, we show that the ERM proteins ezrin and moesin influence the organization and integrity of BCR microclusters. BCR-driven inactivation of ERM proteins is accompanied by a temporary increase in BCR diffusion, followed by BCR immobilization. Disruption of ERM protein function using dominant-negative or constitutively active ezrin constructs or knockdown of ezrin and moesin expression quantitatively and qualitatively alters BCR microcluster formation, antigen aggregation, and downstream BCR signal transduction. Chemical inhibition of actin polymerization also altered the structure and integrity of BCR microclusters. Together, these findings highlight a crucial role for the cortical actin cytoskeleton during B cell spreading and microcluster formation and function.

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Holliday, L. Shannon, Lorraine Perciliano de Faria, and Wellington J. Rody. "Actin and Actin-Associated Proteins in Extracellular Vesicles Shed by Osteoclasts." International Journal of Molecular Sciences 21, no. 1 (December 25, 2019): 158. http://dx.doi.org/10.3390/ijms21010158.

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Extracellular vesicles (EVs) are shed by all eukaryotic cells and have emerged as important intercellular regulators. EVs released by osteoclasts were recently identified as important coupling factors in bone remodeling. They are shed as osteoclasts resorb bone and stimulate osteoblasts to form bone to replace the bone resorbed. We reported the proteomic content of osteoclast EVs with data from two-dimensional, high resolution liquid chromatography/mass spectrometry. In this article, we examine in detail the actin and actin-associated proteins found in osteoclast EVs. Like EVs from other cell types, actin and various actin-associated proteins were abundant. These include components of the polymerization machinery, myosin mechanoenzymes, proteins that stabilize or depolymerize microfilaments, and actin-associated proteins that are involved in regulating integrins. The selective incorporation of actin-associated proteins into osteoclast EVs suggests that they have roles in the formation of EVs and/or the regulatory signaling functions of the EVs. Regulating integrins so that they bind extracellular matrix tightly, in order to attach EVs to the extracellular matrix at specific locations in organs and tissues, is one potential active role for actin-associated proteins in EVs.

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Shen, Xuetong, Ryan Ranallo, Eugene Choi, and Carl Wu. "Involvement of Actin-Related Proteins in ATP-Dependent Chromatin Remodeling." Molecular Cell 12, no. 1 (July 2003): 147–55. http://dx.doi.org/10.1016/s1097-2765(03)00264-8.

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Boyer, Laurie A., and Craig L. Peterson. "Actin-related proteins (Arps): conformational switches for chromatin-remodeling machines?" BioEssays 22, no. 7 (June 23, 2000): 666–72. http://dx.doi.org/10.1002/1521-1878(200007)22:7<666::aid-bies9>3.0.co;2-y.

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Cao, Lingyan, Wenyi Wang, Weiwei Zhang, and Christopher J. Staiger. "Lipid Signaling Requires ROS Production to Elicit Actin Cytoskeleton Remodeling during Plant Innate Immunity." International Journal of Molecular Sciences 23, no. 5 (February 23, 2022): 2447. http://dx.doi.org/10.3390/ijms23052447.

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In terrestrial plants a basal innate immune system, pattern-triggered immunity (PTI), has evolved to limit infection by diverse microbes. The remodeling of actin cytoskeletal arrays is now recognized as a key hallmark event during the rapid host cellular responses to pathogen attack. Several actin binding proteins have been demonstrated to fine tune the dynamics of actin filaments during this process. However, the upstream signals that stimulate actin remodeling during PTI signaling remain poorly characterized. Two second messengers, reactive oxygen species (ROS) and phosphatidic acid (PA), are elevated following pathogen perception or microbe-associated molecular pattern (MAMP) treatment, and the timing of signaling fluxes roughly correlates with actin cytoskeletal rearrangements. Here, we combined genetic analysis, chemical complementation experiments, and quantitative live-cell imaging experiments to test the role of these second messengers in actin remodeling and to order the signaling events during plant immunity. We demonstrated that PHOSPHOLIPASE Dβ (PLDβ) isoforms are necessary to elicit actin accumulation in response to flg22-associated PTI. Further, bacterial growth experiments and MAMP-induced apoplastic ROS production measurements revealed that PLDβ-generated PA acts upstream of ROS signaling to trigger actin remodeling through inhibition of CAPPING PROTEIN (CP) activity. Collectively, our results provide compelling evidence that PLDβ/PA functions upstream of RBOHD-mediated ROS production to elicit actin rearrangements during the innate immune response in Arabidopsis.

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Nemesh, Y. M., and S. V. Kropyvko. "New interactions of invadopodia scaffold protein TKS5 with proteins that take part in actin cytoskeleton reorganization, endo-/exocytosis and membrane remodeling." Visnik ukrains'kogo tovaristva genetikiv i selekcioneriv 16, no. 2 (March 1, 2019): 183–89. http://dx.doi.org/10.7124/visnyk.utgis.16.2.1056.

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Aim. TKS5 is a key scaffold protein of invadopodia. In its absence, the cells completely lose the ability to form invadopodia. This fact makes TKS5 a potential target for cancer cure and one of the central proteins in the investigation of cancer cell invasion. Additionally, the question remains about the function of TKS5 in normal cells. Therefore, in order to extend knowledge about TKS5 role in healthy and invasive cells, we tested the TKS5 interaction with the proteins involved in signal transduction: PLCγ1, SRC, CRK, CSK; the proteins involved in plasma membrane remodeling: AMPH1, BIN1, CIN85, ITSN1, ITSN2; the protein involved in the actin cytoskeleton rearrangement: CTTN. Methods. We used the GST Pull-down assay to identify the protein-protein interaction. Results. We revealed that TKS5 SH3 domains interact with CIN85. There were identified TKS5 interactions with SH3 domains of CTTN, ITSN1, ITSN2, AMPH1 and BIN1. Conclusions. TKS5 interacts with CIN85, CTTN, ITSN1, ITSN2, AMPH1 and BIN1, which take part in membrane remodeling, endo-/exocytosis and actin cytoskeleton rearrangement. Keywords: TKS5, scaffold proteins, actin cytoskeleton, plasma membrane.

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Yumura, Shigehiko, Md Shahabe Uddin Talukder, Mst Shaela Pervin, Md Istiaq Obaidi Tanvir, Takashi Matsumura, Koushiro Fujimoto, Masahito Tanaka, and Go Itoh. "Dynamics of Actin Cytoskeleton and Their Signaling Pathways during Cellular Wound Repair." Cells 11, no. 19 (October 9, 2022): 3166. http://dx.doi.org/10.3390/cells11193166.

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The repair of wounded cell membranes is essential for cell survival. Upon wounding, actin transiently accumulates at the wound site. The loss of actin accumulation leads to cell death. The mechanism by which actin accumulates at the wound site, the types of actin-related proteins participating in the actin remodeling, and their signaling pathways are unclear. We firstly examined how actin accumulates at a wound site in Dictyostelium cells. Actin assembled de novo at the wound site, independent of cortical flow. Next, we searched for actin- and signal-related proteins targeting the wound site. Fourteen of the examined proteins transiently accumulated at different times. Thirdly, we performed functional analyses using gene knockout mutants or specific inhibitors. Rac, WASP, formin, the Arp2/3 complex, profilin, and coronin contribute to the actin dynamics. Finally, we found that multiple signaling pathways related to TORC2, the Elmo/Doc complex, PIP2-derived products, PLA2, and calmodulin are involved in the actin dynamics for wound repair.

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Ram, Rashmi, Andrew P. Wescott, Katherine Varandas, Robert T. Dirksen, and Burns C. Blaxall. "Mena associates with Rac1 and modulates connexin 43 remodeling in cardiomyocytes." American Journal of Physiology-Heart and Circulatory Physiology 306, no. 1 (January 1, 2014): H154—H159. http://dx.doi.org/10.1152/ajpheart.00749.2013.

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Mena, a member of the Ena/VASP family of actin regulatory proteins, modulates microfilaments and interacts with cytoskeletal proteins associated with heart failure. Mena is localized at the intercalated disc (ICD) of adult cardiac myocytes, colocalizing with numerous cytoskeletal proteins. Mena's role in the maintainence of mechanical myocardial stability at the cardiomyocyte ICD remains unknown. We hypothesized that Mena may modulate signals from the sarcolemma to the actin cytoskeleton at the ICD to regulate the expression and localization of connexin 43 (Cx43). The small GTPase Rac1 plays a pivotal role in the regulation of actin cytoskeletal reorganization and mediating morphological and transcriptional changes in cardiomyocytes. We found that Mena is associated with active Rac1 in cardiomyocytes and that RNAi knockdown of Mena increased Rac1 activity significantly. Furthermore, Mena knockdown increased Cx43 expression and altered Cx43 localization and trafficking at the ICD, concomitant with faster intercellular communication, as assessed by dye transfer between cardiomyocyte pairs. In mice overexpressing constitutively active Rac1, left ventricular Mena expression was increased significantly, concomitant with lateral redistribution of Cx43. These results suggest that Mena is a critical regulator of the ICD and is required for normal localization of Cx43 in part via regulation of Rac1.

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Albertinazzi, C., A. Cattelino, and I. de Curtis. "Rac GTPases localize at sites of actin reorganization during dynamic remodeling of the cytoskeleton of normal embryonic fibroblasts." Journal of Cell Science 112, no. 21 (November 1, 1999): 3821–31. http://dx.doi.org/10.1242/jcs.112.21.3821.

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Rac GTP-binding proteins are implicated in the dynamic organization of the actin cytoskeleton, and the mechanisms utilized for this purpose are not understood yet. In this paper we have analysed the effects of the expression of Rac proteins on the organization of the cytoskeleton, and their subcellular distribution in chicken embryo fibroblasts. In these cells, overexpression of wild-type Rac GTPases induces disassembly of stress fibers, and production of long, highly branched actin-rich protrusions, with consequent dramatic changes in cell morphology. The formation of these protrusions is mediated by adhesion to the substrate, and is prevented by incubation with anti-(beta)1 function-blocking antibodies. Rac-mediated cell shape changes require a wild-type GTPase, since expression of constitutively active V12-Rac proteins affects actin organization differently in these cells, without causing alterations in their morphology. Localization studies performed on ventral plasma membranes from fibroblasts transfected with wild-type or mutant GTPases show codistribution of Rac along stress fibers, before their disassembly and the formation of the actin-rich protrusions. These data show a link between Rac protein distribution, and their effects on the actin cytoskeleton. Altogether, our results are indicative of an active role of Rac proteins in stress fiber disassembly, and show that Rac, which can cycle its bound nucleotide, produces unique dynamic effects on actin organization.

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Krueger, Eugene W., James D. Orth, Hong Cao, and Mark A. McNiven. "A Dynamin–Cortactin–Arp2/3 Complex Mediates Actin Reorganization in Growth Factor-stimulated Cells." Molecular Biology of the Cell 14, no. 3 (March 2003): 1085–96. http://dx.doi.org/10.1091/mbc.e02-08-0466.

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The mechanisms by which mammalian cells remodel the actin cytoskeleton in response to motogenic stimuli are complex and a topic of intense study. Dynamin 2 (Dyn2) is a large GTPase that interacts directly with several actin binding proteins, including cortactin. In this study, we demonstrate that Dyn2 and cortactin function to mediate dynamic remodeling of the actin cytoskeleton in response to stimulation with the motogenic growth factor platelet-derived growth factor. On stimulation, Dyn2 and cortactin coassemble into large, circular structures on the dorsal cell surface. These “waves” promote an active reorganization of actin filaments in the anterior cytoplasm and function to disassemble actin stress fibers. Importantly, inhibition of Dyn2 and cortactin function potently blocked the formation of waves and subsequent actin reorganization. These findings demonstrate that cortactin and Dyn2 function together in a supramolecular complex that assembles in response to growth factor stimulation and mediates the remodeling of actin to facilitate lamellipodial protrusion at the leading edge of migrating cells.

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Carraway, Martha Sue, Andrew J. Ghio, Hagir B. Suliman, Jacqueline D. Carter, A. Richard Whorton, and Claude A. Piantadosi. "Carbon monoxide promotes hypoxic pulmonary vascular remodeling." American Journal of Physiology-Lung Cellular and Molecular Physiology 282, no. 4 (April 1, 2002): L693—L702. http://dx.doi.org/10.1152/ajplung.00211.2001.

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CO is a biologically active gas that produces cellular effects by multiple mechanisms. Because cellular binding of CO by heme proteins is increased in hypoxia, we tested the hypothesis that CO interferes with hypoxic pulmonary vascular remodeling in vivo. Rats were exposed to inspired CO (50 parts/million) at sea level or 18,000 ft of altitude [hypobaric hypoxia (HH)], and changes in vessel morphometry and pulmonary pressure-flow relationships were compared with controls. Vascular cell single strand DNA (ssDNA) and proliferating cell nuclear antigen (PCNA) were assessed, and changes in gene and protein expression of smooth muscle α-actin (sm-α-actin), β-actin, and heme oxygenase-1 (HO-1) were evaluated by Western analysis, RT-PCR, and immunohistochemistry. After 21 days of HH, vascular pressure at constant flow and vessel wall thickness increased and lumen diameter of small arteries decreased significantly. The presence of CO, however, further increased both pulmonary vascular resistance (PVR) and the number of small muscular vessels compared with HH alone. CO + HH also increased vascular PCNA and nuclear ssDNA expression compared with hypoxia, suggesting accelerated cell turnover. CO in hypoxia downregulated sm-α-actin and strongly upregulated β-actin. CO also increased lung HO activity and HO-1 mRNA and protein expression in small pulmonary arteries during hypoxia. These data indicate an overall propensity of CO in HH to promote vascular remodeling and increase PVR in vivo.

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McDonald, Darin, Gustavo Carrero, Christi Andrin, Gerda de Vries, and Michael J. Hendzel. "Nucleoplasmic β-actin exists in a dynamic equilibrium between low-mobility polymeric species and rapidly diffusing populations." Journal of Cell Biology 172, no. 4 (February 13, 2006): 541–52. http://dx.doi.org/10.1083/jcb.200507101.

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β-Actin, once thought to be an exclusively cytoplasmic protein, is now known to have important functions within the nucleus. Nuclear β-actin associates with and functions in chromatin remodeling complexes, ribonucleic acid polymerase complexes, and at least some ribonucleoproteins. Proteins involved in regulating actin polymerization are also found in the interphase nucleus. We define the dynamic properties of nuclear actin molecules using fluorescence recovery after photobleaching. Our results indicate that actin and actin-containing complexes are reduced in their mobility through the nucleoplasm diffusing at ∼0.5 μm2 s−1. We also observed that ∼20% of the total nuclear actin pool has properties of polymeric actin that turns over rapidly. This pool could be detected in endogenous nuclear actin by using fluorescent polymeric actin binding proteins and was sensitive to drugs that alter actin polymerization. Our results validate previous reports of polymeric forms of nuclear actin observed in fixed specimens and reveal that these polymeric forms are very dynamic.

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Hudson, Andrew M., and Lynn Cooley. "Drosophila Kelch functions with Cullin-3 to organize the ring canal actin cytoskeleton." Journal of Cell Biology 188, no. 1 (January 11, 2010): 29–37. http://dx.doi.org/10.1083/jcb.200909017.

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Drosophila melanogaster Kelch (KEL) is the founding member of a diverse protein family defined by a repeated sequence motif known as the KEL repeat (KREP). Several KREP proteins, including Drosophila KEL, bind filamentous actin (F-actin) and contribute to its organization. Recently, a subset of KREP proteins has been shown to function as substrate adaptor proteins for cullin-RING (really interesting new gene) ubiquitin E3 ligases. In this study, we demonstrate that association of Drosophila KEL with Cullin-3, likely in a cullin-RING ligase, is essential for the growth of Drosophila female germline ring canals. These results suggest a role for protein ubiquitylation in the remodeling of a complex F-actin cytoskeletal structure.

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Ma, Zhiming, Yanbiao Sun, Xinlu Zhu, Liang Yang, Xu Chen, and Yansong Miao. "Membrane nanodomains modulate formin condensation for actin remodeling in Arabidopsis innate immune responses." Plant Cell 34, no. 1 (November 2, 2021): 374–94. http://dx.doi.org/10.1093/plcell/koab261.

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Abstract The assembly of macromolecules on the plasma membrane concentrates cell surface biomolecules into nanometer- to micrometer-scale clusters (nano- or microdomains) that help the cell initiate or respond to signals. In plant–microbe interactions, the actin cytoskeleton undergoes rapid remodeling during pathogen-associated molecular pattern-triggered immunity (PTI). The nanoclustering of formin-actin nucleator proteins at the cell surface has been identified as underlying actin nucleation during plant innate immune responses. Here, we show that the condensation of nanodomain constituents and the self-assembly of remorin proteins enables this mechanism of controlling formin condensation and activity during innate immunity in Arabidopsis thaliana. Through intrinsically disordered region-mediated remorin oligomerization and formin interaction, remorin gradually recruits and condenses formins upon PTI activation in lipid bilayers, consequently increasing actin nucleation in a time-dependent manner postinfection. Such nanodomain- and remorin-mediated regulation of plant surface biomolecules is expected to be a general feature of plant innate immune responses that creates spatially separated biochemical compartments and fine tunes membrane physicochemical properties for transduction of immune signals in the host.

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Gerthoffer, William T., and Susan J. Gunst. "Invited Review: Focal adhesion and small heat shock proteins in the regulation of actin remodeling and contractility in smooth muscle." Journal of Applied Physiology 91, no. 2 (August 1, 2001): 963–72. http://dx.doi.org/10.1152/jappl.2001.91.2.963.

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Smooth muscle cells are able to adapt rapidly to chemical and mechanical signals impinging on the cell surface. It has been suggested that dynamic changes in the actin cytoskeleton contribute to the processes of contractile activation and mechanical adaptation in smooth muscle. In this review, evidence for functionally important changes in actin polymerization during smooth muscle contraction is summarized. The functions and regulation of proteins associated with “focal adhesion complexes” (membrane-associated dense plaques) in differentiated smooth muscle, including integrins, focal adhesion kinase (FAK), c-Src, paxillin, and the 27-kDa small heat shock protein (HSP27) are described. Integrins in smooth muscles are key elements of mechanotransduction pathways that communicate with and are regulated by focal adhesion proteins that include FAK, c-Src, and paxillin as well as proteins known to mediate cytoskeletal remodeling. Evidence that functions of FAK and c-Src protein kinases are closely intertwined is discussed as well as evidence that focal adhesion proteins mediate key signal transduction events that regulate actin remodeling and contraction. HSP27 is reviewed as a potentially significant effector protein that may regulate actin dynamics and cross-bridge function in response to activation of p21-activated kinase and the p38 mitogen-activated protein kinase signaling pathway by signaling pathways linked to integrin proteins. These signaling pathways are only part of a large number of yet to be defined pathways that mediate acute adaptive responses of the cytoskeleton in smooth muscle to environmental stimuli.

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Johnson, Jennifer L., Jlenia Monfregola, Gennaro Napolitano, William B. Kiosses, and Sergio D. Catz. "Vesicular trafficking through cortical actin during exocytosis is regulated by the Rab27a effector JFC1/Slp1 and the RhoA-GTPase–activating protein Gem-interacting protein." Molecular Biology of the Cell 23, no. 10 (May 15, 2012): 1902–16. http://dx.doi.org/10.1091/mbc.e11-12-1001.

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Cytoskeleton remodeling is important for the regulation of vesicular transport associated with exocytosis, but a direct association between granular secretory proteins and actin-remodeling molecules has not been shown, and this mechanism remains obscure. Using a proteomic approach, we identified the RhoA-GTPase–activating protein Gem-interacting protein (GMIP) as a factor that associates with the Rab27a effector JFC1 and modulates vesicular transport and exocytosis. GMIP down-regulation induced RhoA activation and actin polymerization. Importantly, GMIP-down-regulated cells showed impaired vesicular transport and exocytosis, while inhibition of the RhoA-signaling pathway induced actin depolymerization and facilitated exocytosis. We show that RhoA activity polarizes around JFC1-containing secretory granules, suggesting that it may control directionality of granule movement. Using quantitative live-cell microscopy, we show that JFC1-containing secretory organelles move in areas near the plasma membrane deprived of polymerized actin and that dynamic vesicles maintain an actin-free environment in their surroundings. Supporting a role for JFC1 in RhoA inactivation and actin remodeling during exocytosis, JFC1 knockout neutrophils showed increased RhoA activity, and azurophilic granules were unable to traverse cortical actin in cells lacking JFC1. We propose that during exocytosis, actin depolymerization commences near the secretory organelle, not the plasma membrane, and that secretory granules use a JFC1- and GMIP-dependent molecular mechanism to traverse cortical actin.

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Latreille, Mathieu, Afnan Abu-Thuraia, Rossella Oliva, Dongmei Zuo, and Louise Larose. "Casein Kinase Iγ2 Impairs Fibroblasts Actin Stress Fibers Formation and Delays Cell Cycle Progression in G1." International Journal of Cell Biology 2012 (2012): 1–15. http://dx.doi.org/10.1155/2012/684684.

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Actin cytoskeleton remodeling is under the regulation of multiple proteins with various activities. Here, we demonstrate that theγ2 isoform of Casein Kinase I (CKIγ2) is part of a novel molecular path regulating the formation of actin stress fibers. We show that overexpression of CKIγ2 in fibroblasts alters cell morphology by impairing actin stress fibers formation. We demonstrate that this is concomitant with increased phosphorylation of the CDK inhibitorp27Kipand lower levels of activated RhoA, and is dependent on CKIγ2 catalytic activity. Moreover, we report that roscovitine, a potent inhibitor of cyclin-dependent kinases, including Cdk5, decreasesp27Kipprotein levels and restores actin stress fibers formation in CKIγ2 overexpressing cells, suggesting the existence of a CKIγ2-Cdk5-p27Kip-RhoA pathway in regulating actin remodeling. On the other hand, we also show that in a manner independent of its catalytic activity, CKIγ2 delays cell cycle progression through G1. Collectively our findings reveal that CKIγ2 is a novel player in the control of actin cytoskeleton dynamics and cell proliferation.

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Maxeiner, Sebastian, Nian Shi, Carmen Schalla, Guelcan Aydin, Mareike Hoss, Simon Vogel, Martin Zenke, and Antonio S. Sechi. "Crucial role for the LSP1–myosin1e bimolecular complex in the regulation of Fcγ receptor–driven phagocytosis." Molecular Biology of the Cell 26, no. 9 (May 2015): 1652–64. http://dx.doi.org/10.1091/mbc.e14-05-1005.

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Actin cytoskeleton remodeling is fundamental for Fcγ receptor–driven phagocytosis. In this study, we find that the leukocyte-specific protein 1 (LSP1) localizes to nascent phagocytic cups during Fcγ receptor–mediated phagocytosis, where it displays the same spatial and temporal distribution as the actin cytoskeleton. Down-regulation of LSP1 severely reduces the phagocytic activity of macrophages, clearly demonstrating a crucial role for this protein in Fcγ receptor–mediated phagocytosis. We also find that LSP1 binds to the class I molecular motor myosin1e. LSP1 interacts with the SH3 domain of myosin1e, and the localization and dynamics of both proteins in nascent phagocytic cups mirror those of actin. Furthermore, inhibition of LSP1–myosin1e and LSP1–actin interactions profoundly impairs pseudopodial formation around opsonized targets and their subsequent internalization. Thus the LSP1–myosin1e bimolecular complex plays a pivotal role in the regulation of actin cytoskeleton remodeling during Fcγ receptor–driven phagocytosis.

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Moseley, James B., and Bruce L. Goode. "The Yeast Actin Cytoskeleton: from Cellular Function to Biochemical Mechanism." Microbiology and Molecular Biology Reviews 70, no. 3 (September 2006): 605–45. http://dx.doi.org/10.1128/mmbr.00013-06.

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SUMMARY All cells undergo rapid remodeling of their actin networks to regulate such critical processes as endocytosis, cytokinesis, cell polarity, and cell morphogenesis. These events are driven by the coordinated activities of a set of 20 to 30 highly conserved actin-associated proteins, in addition to many cell-specific actin-associated proteins and numerous upstream signaling molecules. The combined activities of these factors control with exquisite precision the spatial and temporal assembly of actin structures and ensure dynamic turnover of actin structures such that cells can rapidly alter their cytoskeletons in response to internal and external cues. One of the most exciting principles to emerge from the last decade of research on actin is that the assembly of architecturally diverse actin structures is governed by highly conserved machinery and mechanisms. With this realization, it has become apparent that pioneering efforts in budding yeast have contributed substantially to defining the universal mechanisms regulating actin dynamics in eukaryotes. In this review, we first describe the filamentous actin structures found in Saccharomyces cerevisiae (patches, cables, and rings) and their physiological functions, and then we discuss in detail the specific roles of actin-associated proteins and their biochemical mechanisms of action.

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DiPaolo, Brian C., Nurit Davidovich, Marcelo G. Kazanietz, and Susan S. Margulies. "Rac1 pathway mediates stretch response in pulmonary alveolar epithelial cells." American Journal of Physiology-Lung Cellular and Molecular Physiology 305, no. 2 (July 15, 2013): L141—L153. http://dx.doi.org/10.1152/ajplung.00298.2012.

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Alveolar epithelial cells (AECs) maintain the pulmonary blood-gas barrier integrity with gasketlike intercellular tight junctions (TJ) that are anchored internally to the actin cytoskeleton. We have previously shown that AEC monolayers stretched cyclically and equibiaxially undergo rapid magnitude- and frequency-dependent actin cytoskeletal remodeling to form perijunctional actin rings (PJARs). In this work, we show that even 10 min of stretch induced increases in the phosphorylation of Akt and LIM kinase (LIMK) and decreases in cofilin phosphorylation, suggesting that the Rac1/Akt pathway is involved in these stretch-mediated changes. We confirmed that Rac1 inhibitors wortmannin or EHT-1864 decrease stretch-stimulated Akt and LIMK phosphorylation and that Rac1 agonists PIP3 or PDGF increase phosphorylation of these proteins in unstretched cells. We also confirmed that Rac1 pathway inhibition during stretch modulated stretch-induced changes in occludin content and monolayer permeability, actin remodeling and PJAR formation, and cell death. As further validation, overexpression of Rac GTPase-activating protein β2-chimerin also preserved monolayer barrier properties in stretched monolayers. In summary, our data suggest that constitutive activity of Rac1, which is necessary for stretch-induced activation of the Rac1 downstream proteins, mediates stretch-induced increases in permeability and PJAR formation.

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Zakrzewski, Przemysław, Marta Lenartowska, and Folma Buss. "Diverse functions of myosin VI in spermiogenesis." Histochemistry and Cell Biology 155, no. 3 (January 2, 2021): 323–40. http://dx.doi.org/10.1007/s00418-020-01954-x.

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AbstractSpermiogenesis is the final stage of spermatogenesis, a differentiation process during which unpolarized spermatids undergo excessive remodeling that results in the formation of sperm. The actin cytoskeleton and associated actin-binding proteins play crucial roles during this process regulating organelle or vesicle delivery/segregation and forming unique testicular structures involved in spermatid remodeling. In addition, several myosin motor proteins including MYO6 generate force and movement during sperm differentiation. MYO6 is highly unusual as it moves towards the minus end of actin filaments in the opposite direction to other myosin motors. This specialized feature of MYO6 may explain the many proposed functions of this myosin in a wide array of cellular processes in animal cells, including endocytosis, secretion, stabilization of the Golgi complex, and regulation of actin dynamics. These diverse roles of MYO6 are mediated by a range of specialized cargo-adaptor proteins that link this myosin to distinct cellular compartments and processes. During sperm development in a number of different organisms, MYO6 carries out pivotal functions. In Drosophila, the MYO6 ortholog regulates actin reorganization during spermatid individualization and male KO flies are sterile. In C. elegans, the MYO6 ortholog mediates asymmetric segregation of cytosolic material and spermatid budding through cytokinesis, whereas in mice, this myosin regulates assembly of highly specialized actin-rich structures and formation of membrane compartments to allow the formation of fully differentiated sperm. In this review, we will present an overview and compare the diverse function of MYO6 in the specialized adaptations of spermiogenesis in flies, worms, and mammals.

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Nakamura, Mitsutoshi, Jeffrey M. Verboon, and Susan M. Parkhurst. "Prepatterning by RhoGEFs governs Rho GTPase spatiotemporal dynamics during wound repair." Journal of Cell Biology 216, no. 12 (September 18, 2017): 3959–69. http://dx.doi.org/10.1083/jcb.201704145.

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Like tissues, single cells are subjected to continual stresses and damage. As such, cells have a robust wound repair mechanism comprised of dynamic membrane resealing and cortical cytoskeletal remodeling. One group of proteins, the Rho family of small guanosine triphosphatases (GTPases), is critical for this actin and myosin cytoskeletal response in which they form distinct dynamic spatial and temporal patterns/arrays surrounding the wound. A key mechanistic question, then, is how these GTPase arrays are formed. Here, we show that in the Drosophila melanogaster cell wound repair model Rho GTPase arrays form in response to prepatterning by Rho guanine nucleotide exchange factors (RhoGEFs), a family of proteins involved in the activation of small GTPases. Furthermore, we show that Annexin B9, a member of a class of proteins associated with the membrane resealing, is involved in an early, Rho family–independent, actin stabilization that is integral to the formation of one RhoGEF array. Thus, Annexin proteins may link membrane resealing to cytoskeletal remodeling processes in single cell wound repair.

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Tessarz, Peter, Michael Schwarz, Axel Mogk, and Bernd Bukau. "The Yeast AAA+ Chaperone Hsp104 Is Part of a Network That Links the Actin Cytoskeleton with the Inheritance of Damaged Proteins." Molecular and Cellular Biology 29, no. 13 (April 27, 2009): 3738–45. http://dx.doi.org/10.1128/mcb.00201-09.

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ABSTRACT The yeast AAA+ chaperone Hsp104 is essential for the development of thermotolerance and for the inheritance of prions. Recently, Hsp104, together with the actin cytoskeleton, has been implicated in the asymmetric distribution of carbonylated proteins. Here, we investigated the interplay between Hsp104 and actin by using a dominant-negative variant of Hsp104 (HAP/ClpP) that degrades substrate proteins instead of remodeling them. Coexpression of HAP/ClpP causes defects in morphology and the actin cytoskeleton. Taking a candidate approach, we identified Spa2, a member of the polarisome complex, as an Hsp104 substrate. Furthermore, we provided genetic evidence that links Spa2 and Hsp104 to Hof1, a member of the cytokinesis machinery. Spa2 and Hof1 knockout cells are affected in the asymmetric distribution of damaged proteins, suggesting that Hsp104, Spa2, and Hof1 are members of a network controlling the inheritance of carbonylated proteins.

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Hui, Justin, Viktor Stjepić, Mitsutoshi Nakamura, and Susan M. Parkhurst. "Wrangling Actin Assemblies: Actin Ring Dynamics during Cell Wound Repair." Cells 11, no. 18 (September 6, 2022): 2777. http://dx.doi.org/10.3390/cells11182777.

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To cope with continuous physiological and environmental stresses, cells of all sizes require an effective wound repair process to seal breaches to their cortex. Once a wound is recognized, the cell must rapidly plug the injury site, reorganize the cytoskeleton and the membrane to pull the wound closed, and finally remodel the cortex to return to homeostasis. Complementary studies using various model organisms have demonstrated the importance and complexity behind the formation and translocation of an actin ring at the wound periphery during the repair process. Proteins such as actin nucleators, actin bundling factors, actin-plasma membrane anchors, and disassembly factors are needed to regulate actin ring dynamics spatially and temporally. Notably, Rho family GTPases have been implicated throughout the repair process, whereas other proteins are required during specific phases. Interestingly, although different models share a similar set of recruited proteins, the way in which they use them to pull the wound closed can differ. Here, we describe what is currently known about the formation, translocation, and remodeling of the actin ring during the cell wound repair process in model organisms, as well as the overall impact of cell wound repair on daily events and its importance to our understanding of certain diseases and the development of therapeutic delivery modalities.

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Bongiovanni, Antonella, Daniele P. Romancino, Yvan Campos, Gaetano Paterniti, Xiaohui Qiu, Simon Moshiach, Valentina Di Felice, Naja Vergani, Duran Ustek, and Alessandra d'Azzo. "Alix Protein Is Substrate of Ozz-E3 Ligase and Modulates Actin Remodeling in Skeletal Muscle." Journal of Biological Chemistry 287, no. 15 (February 13, 2012): 12159–71. http://dx.doi.org/10.1074/jbc.m111.297036.

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Alix/AIP1 is a multifunctional adaptor protein that participates in basic cellular processes, including membrane trafficking and actin cytoskeleton assembly, by binding selectively to a variety of partner proteins. However, the mechanisms regulating Alix turnover, subcellular distribution, and function in muscle cells are unknown. We now report that Alix is expressed in skeletal muscle throughout myogenic differentiation. In myotubes, a specific pool of Alix colocalizes with Ozz, the substrate-binding component of the muscle-specific ubiquitin ligase complex Ozz-E3. We found that interaction of the two endogenous proteins in the differentiated muscle fibers changes Alix conformation and promotes its ubiquitination. This in turn regulates the levels of the protein in specific subcompartments, in particular the one containing the actin polymerization factor cortactin. In Ozz−/− myotubes, the levels of filamentous (F)-actin is perturbed, and Alix accumulates in large puncta positive for cortactin. In line with this observation, we show that the knockdown of Alix expression in C2C12 muscle cells affects the amount and distribution of F-actin, which consequently leads to changes in cell morphology, impaired formation of sarcolemmal protrusions, and defective cell motility. These findings suggest that the Ozz-E3 ligase regulates Alix at sites where the actin cytoskeleton undergoes remodeling.

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Tanna, Christine, Louisa Goss, Calvin Ludwig, and Pei-Wen Chen. "Arf•GAPs as Regulators of the Actin Cytoskeleton—An Update." International Journal of Molecular Sciences 20, no. 2 (January 21, 2019): 442. http://dx.doi.org/10.3390/ijms20020442.

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Arf•GTPase-activating proteins (Arf•GAPs) control the activity of ADP-ribosylation factors (Arfs) by inducing GTP hydrolysis and participate in a diverse array of cellular functions both through mechanisms that are dependent on and independent of their Arf•GAP activity. A number of these functions hinge on the remodeling of actin filaments. Accordingly, some of the effects exerted by Arf•GAPs involve proteins known to engage in regulation of the actin dynamics and architecture, such as Rho family proteins and nonmuscle myosin 2. Circular dorsal ruffles (CDRs), podosomes, invadopodia, lamellipodia, stress fibers and focal adhesions are among the actin-based structures regulated by Arf•GAPs. Arf•GAPs are thus important actors in broad functions like adhesion and motility, as well as the specialized functions of bone resorption, neurite outgrowth, and pathogen internalization by immune cells. Arf•GAPs, with their multiple protein-protein interactions, membrane-binding domains and sites for post-translational modification, are good candidates for linking the changes in actin to the membrane. The findings discussed depict a family of proteins with a critical role in regulating actin dynamics to enable proper cell function.

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Sherlekar, Aparna, and Richa Rikhy. "Syndapin promotes pseudocleavage furrow formation by actin organization in the syncytial Drosophila embryo." Molecular Biology of the Cell 27, no. 13 (July 2016): 2064–79. http://dx.doi.org/10.1091/mbc.e15-09-0656.

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Coordinated membrane and cytoskeletal remodeling activities are required for membrane extension in processes such as cytokinesis and syncytial nuclear division cycles in Drosophila. Pseudocleavage furrow membranes in the syncytial Drosophila blastoderm embryo show rapid extension and retraction regulated by actin-remodeling proteins. The F-BAR domain protein Syndapin (Synd) is involved in membrane tubulation, endocytosis, and, uniquely, in F-actin stability. Here we report a role for Synd in actin-regulated pseudocleavage furrow formation. Synd localized to these furrows, and its loss resulted in short, disorganized furrows. Synd presence was important for the recruitment of the septin Peanut and distribution of Diaphanous and F-actin at furrows. Synd and Peanut were both absent in furrow-initiation mutants of RhoGEF2 and Diaphanous and in furrow-progression mutants of Anillin. Synd overexpression in rhogef2 mutants reversed its furrow-extension phenotypes, Peanut and Diaphanous recruitment, and F-actin organization. We conclude that Synd plays an important role in pseudocleavage furrow extension, and this role is also likely to be crucial in cleavage furrow formation during cell division.

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von Arx, P., S. Bantle, T. Soldati, and J. C. Perriard. "Dominant negative effect of cytoplasmic actin isoproteins on cardiomyocyte cytoarchitecture and function." Journal of Cell Biology 131, no. 6 (December 15, 1995): 1759–73. http://dx.doi.org/10.1083/jcb.131.6.1759.

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The intracompartmental sorting and functional consequences of ectopic expression of the six vertebrate actin isoforms was investigated in different types of cultured cells. In transfected fibroblasts all isoactin species associated with the endogenous microfilament cytoskeleton, even though cytoplasmic actins also showed partial localization to peripheral submembranous sites. Functional and structural studies were performed in neonatal and adult rat cardiomyocytes. All the muscle isoactin constructs sorted preferentially to sarcomeric sites and, to a lesser extent, also to stress-fiber-like structures. The expression of muscle actins did not interfere with cell contractility, and did not disturb the localization of endogenous sarcomeric proteins. In sharp contrast, ectopic expression of the two cytoplasmic actin isoforms resulted in rapid cessation of cellular contractions and induced severe morphological alterations characterized by an exceptional outgrowth of filopodia and cell flattening. Quantitative analysis in neonatal cardiomyocytes indicated that the levels of accumulation of the different isoactins are very similar and cannot be responsible for the observed isoproteins-specific effects. Structural analysis revealed a remodeling of the cytoarchitecture including a specific alteration of sarcomeric organization; proteins constituting the sarcomeric thin filaments relocated to nonmyofibrillar sites while thick filaments and titin remained unaffected. Experiments with chimeric proteins strongly suggest that isoform specific residues in the carboxy-terminal portion of the cytoplasmic actins are responsible for the dominant negative effects on function and morphology.

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Muranova, Lydia K., Vladislav M. Shatov, and Nikolai B. Gusev. "Role of Small Heat Shock Proteins in the Remodeling of Actin Microfilaments." Biochemistry (Moscow) 87, no. 8 (August 2022): 800–811. http://dx.doi.org/10.1134/s0006297922080119.

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Turegun, Bengi, David J. Kast, and Roberto Dominguez. "Interactions of Nuclear Actin-Related Proteins with SWI/SNF Chromatin-Remodeling Complexes." Biophysical Journal 104, no. 2 (January 2013): 582a. http://dx.doi.org/10.1016/j.bpj.2012.11.3231.

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Sidhu, Navneet, and John F. Dawson. "A crosslinked and ribosylated actin trimer does not interact productively with myosin." Biochemistry and Cell Biology 97, no. 2 (April 2019): 140–47. http://dx.doi.org/10.1139/bcb-2018-0082.

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A purified F-actin-derived actin trimer that interacts with end-binding proteins did not activate or bind the side-binding protein myosin under rigor conditions. Remodeling of the actin trimer by the binding of gelsolin did not rescue myosin binding, nor did the use of different means of inhibiting the polymerization of the trimer. Our results demonstrate that ADP-ribosylation on all actin subunits of an F-actin-derived trimer inhibits myosin binding and that the binding of DNase-I to the pointed end subunits of a crosslinked trimer also remodels the myosin binding site. Taken together, this work highlights the need for a careful balance between modification of actin subunits and maintaining protein–protein interactions to produce a physiologically relevant short F-actin complex.

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Aizawa, H., Y. Fukui, and I. Yahara. "Live dynamics of Dictyostelium cofilin suggests a role in remodeling actin latticework into bundles." Journal of Cell Science 110, no. 19 (October 1, 1997): 2333–44. http://dx.doi.org/10.1242/jcs.110.19.2333.

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Cofilin, an indispensable, actin-regulating protein represents the ‘cofilin family’ of actin-binding proteins existing in a wide variety of organisms. Our previous and other in vitro studies have implied that cofilin can accelerate transformation of filamentous (F)-actin and (alpha)-actinin latticework into bundles, and overexpression of cofilin induces formation of F-actin bundles in Dictyostelium. Here we expressed an Aequorea green fluorescent protein (GFP)-Dictyostelium cofilin fusion protein in Dictyostelium, and observed the live dynamics to examine the physiological function of cofilin. We show that purified GFP-cofilin binds to actin filaments and decreases the apparent viscosity of actin solution in a similar manner to authentic Dictyostelium cofilin. Expressed GFP-cofilin exhibits normal actin-binding activities in the cytoplasm as represented by incorporation into the actin rods induced with dimethyl sulfoxide. Free moving cells form a crown-like cortical structure on the dorsal surface, and GFP-cofilin exhibits dynamic assembly into actin bundles being formed beneath the cortex. During phagocytosis, GFP-cofilin accumulates into actin bundles formed in the region underlying the phagocytic cups. In cells chemotactically activated with cyclic AMP, GFP-cofilin exhibits a high level of accumulation in projecting leading edges. When the chemo-attraction is experimentally changed, the redistribution of GFP-cofilin towards the new pseudopod occurs in a matter of 30–60 seconds. These results demonstrate that cofilin plays a crucial role in vivo in rapid remodeling of the cortical actin meshwork into bundles.

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Aseervatham, Jaya. "Cytoskeletal Remodeling in Cancer." Biology 9, no. 11 (November 7, 2020): 385. http://dx.doi.org/10.3390/biology9110385.

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Successful metastasis depends on cell invasion, migration, host immune escape, extravasation, and angiogenesis. The process of cell invasion and migration relies on the dynamic changes taking place in the cytoskeletal components; actin, tubulin and intermediate filaments. This is possible due to the plasticity of the cytoskeleton and coordinated action of all the three, is crucial for the process of metastasis from the primary site. Changes in cellular architecture by internal clues will affect the cell functions leading to the formation of different protrusions like lamellipodia, filopodia, and invadopodia that help in cell migration eventually leading to metastasis, which is life threatening than the formation of neoplasms. Understanding the signaling mechanisms involved, will give a better insight of the changes during metastasis, which will eventually help targeting proteins for treatment resulting in reduced mortality and longer survival.

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Cotton, Mathieu, Pierre-Luc Boulay, Tanguy Houndolo, Nicolas Vitale, Julie A. Pitcher, and Audrey Claing. "Endogenous ARF6 Interacts with Rac1 upon Angiotensin II Stimulation to Regulate Membrane Ruffling and Cell Migration." Molecular Biology of the Cell 18, no. 2 (February 2007): 501–11. http://dx.doi.org/10.1091/mbc.e06-06-0567.

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ARF6 and Rac1 are small GTPases known to regulate remodelling of the actin cytoskeleton. Here, we demonstrate that these monomeric G proteins are sequentially activated when HEK 293 cells expressing the angiotensin type 1 receptor (AT1R) are stimulated with angiotensin II (Ang II). After receptor activation, ARF6 and Rac1 transiently form a complex. Their association is, at least in part, direct and dependent on the nature of the nucleotide bound to both small G proteins. ARF6-GTP preferentially interacts with Rac1-GDP. AT1R expressing HEK293 cells ruffle, form membrane protrusions, and migrate in response to agonist treatment. ARF6, but not ARF1, depletion using small interfering RNAs recapitulates the ruffling and migratory phenotype observed after Ang II treatment. These results suggest that ARF6 depletion or Ang II treatment are functionally equivalent and point to a role for endogenous ARF6 as an inhibitor of Rac1 activity. Taken together, our findings reveal a novel function of endogenously expressed ARF6 and demonstrate that by interacting with Rac1, this small GTPase is a central regulator of the signaling pathways leading to actin remodeling.

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Journal articles on the topic 'Actin remodeling proteins'

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