title: ADP-ribosylation factor 6 regulates actin cytoskeleton remodeling in coordination with Rac1 and RhoA.
abstract: In this study, we have documented an essential role for ADP-ribosylation factor 6 (ARF6) in cell surface remodeling in response to physiological stimulus and in the down regulation of stress fiber formation. We demonstrate that the G-protein-coupled receptor agonist bombesin triggers the redistribution of ARF6- and Rac1-containing endosomal vesicles to the cell surface. This membrane redistribution was accompanied by cortical actin rearrangements and was inhibited by dominant negative ARF6, implying that bombesin is a physiological trigger of ARF6 activation. Furthermore, these studies provide a new model for bombesin-induced Rac1 activation that involves ARF6-regulated endosomal recycling. The bombesin-elicited translocation of vesicular ARF6 was mimicked by activated Galphaq and was partially inhibited by expression of RGS2, which down regulates Gq function. This suggests that Gq functions as an upstream regulator of ARF6 activation. The ARF6-induced peripheral cytoskeletal rearrangements were accompanied by a depletion of stress fibers. Moreover, cells expressing activated ARF6 resisted the formation of stress fibers induced by lysophosphatidic acid. We show that the ARF6-dependent inhibition of stress fiber formation was due to an inhibition of RhoA activation and was overcome by expression of a constitutively active RhoA mutant. The latter observations demonstrate that activation of ARF6 down regulates Rho signaling. Our findings underscore the potential roles of ARF6, Rac1, and RhoA in the coordinated regulation of cytoskeletal remodeling.
authors.affiliation: Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556-0369, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: Boshans
authors.forename: S
authors.initials: S
authors.lastname: Szanto
authors.forename: L
authors.initials: L
authors.lastname: van Aelst
authors.forename: C
authors.initials: C
authors.lastname: D'Souza-Schorey
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001839:Bombesin / Q000494:pharmacology; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D003599:Cytoskeleton / Q000378:metabolism* / Q000648:ultrastructure; D011992:Endosomes / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000089982:ADP-Ribosylation Factor 6; D000199:Actins; D004815:Epidermal Growth Factor; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020727:ADP-Ribosylation Factors; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein; D001839:Bombesin