title: Rho GTPases and the downstream effectors actin-related protein 2/3 (Arp2/3) complex and myosin II induce membrane fusion at self-contacts.
abstract: Actin regulation is required for membrane activities that drive cell adhesion and migration. The Rho GTPase family plays critical roles in actin and membrane dynamics; however, the roles of the Rho GTPase family are not limited to cell adhesion and migration. Using micron-sized obstacles to induce the formation of self-contacts in epithelial cells, we previously showed that self-adhesion is distinct from cell-to-cell adhesion in that self-contacts are eliminated by membrane fusion. In the current study, we identified Rho GTPases, RhoA, Rac1, and Cdc42, as potential upstream regulators of membrane fusion. The RhoA downstream effector myosin II is required for fusion as the expression of mutant myosin light chain reduced membrane fusion. Furthermore, an inhibitor of the Arp2/3 complex, a downstream effector of Rac1 and Cdc42, also reduced self-contact-induced membrane fusion. At self-contacts, while the concentration of E-cadherin diminished, the intensity of GFP-tagged Arp3 rapidly fluctuated then decreased and stabilized after membrane fusion. Taken together, these data suggest that the Arp2/3 complex-mediated actin polymerization brings two opposing membranes into close apposition by possibly excluding E-cadherin from contact sites, thus promoting membrane fusion at self-contacts.
authors.affiliation: From the Department of Biomedical Engineering, University of California, Davis, California 95616.
authors.forename: Grant M
authors.initials: GM
authors.lastname: Sumida
authors.affiliation: From the Department of Biomedical Engineering, University of California, Davis, California 95616 syamada@ucdavis.edu.
authors.forename: Soichiro
authors.initials: S
authors.lastname: Yamada
mesh_terms: D051377:Actin-Related Protein 2 / Q000378:metabolism*; D051378:Actin-Related Protein 3 / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism; D007365:Intercellular Junctions / Q000378:metabolism; D061985:Madin Darby Canine Kidney Cells; D008561:Membrane Fusion; D024462:Myosin Type II / Q000378:metabolism*; D055503:Protein Multimerization; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; D015820:Cadherins; D024462:Myosin Type II; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein
keywords: Actin; Arp2/3 Complex; Cadherin-1 (CDH1) (Epithelial Cadherin) (E-cadherin); Membrane Fusion; Small GTPase