title: MSE55, a Cdc42 effector protein, induces long cellular extensions in fibroblasts.
abstract: Cdc42 is a member of the Rho GTPase family that regulates multiple cellular activities, including actin polymerization, kinase-signaling activation, and cell polarization. MSE55 is a nonkinase CRIB (Cdc42/Rac interactive-binding) domain-containing molecule of unknown function. Using glutathione S-transferase-capture experiments, we show that MSE55 binds to Cdc42 in a GTP-dependent manner. MSE55 binding to Cdc42 required an intact CRIB domain, because a MSE55 CRIB domain mutant no longer interacted with Cdc42. To study the function of MSE55 we transfected either wild-type MSE55 or a MSE55 CRIB mutant into mammalian cells. In Cos-7 cells, wild-type MSE55 localized at membrane ruffles and increased membrane actin polymerization, whereas expression of the MSE55 CRIB mutant showed fewer membrane ruffles. In contrast to these results, MSE55 induced the formation of long, actin-based protrusions in NIH 3T3 cells as detected by immunofluorescence and live-cell video microscopy. MSE55-induced protrusion formation was blocked by expression of dominant-negative N17Cdc42, but not by expression of dominant-negative N17Rac. These findings indicate that MSE55 is a Cdc42 effector protein that mediates actin cytoskeleton reorganization at the plasma membrane.
authors.affiliation: Department of Biochemistry and Molecular Biology and Lombardi Cancer Center, Georgetown University Medical Center, Washington, DC 20007, USA. burbelop@medlib.georgetown.edu
authors.forename: P D
authors.initials: PD
authors.lastname: Burbelo
authors.forename: D M
authors.initials: DM
authors.lastname: Snow
authors.forename: W
authors.initials: W
authors.lastname: Bahou
authors.forename: S
authors.initials: S
authors.lastname: Spiegel
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001798:Blood Proteins / Q000235:genetics / Q000378:metabolism*; D019556:COS Cells; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000502:physiology / Q000648:ultrastructure; D003598:Cytoskeletal Proteins; D005347:Fibroblasts / Q000648:ultrastructure; D020549:GTP Phosphohydrolase Activators; D020558:GTP Phosphohydrolases; D020555:GTP-Binding Protein Regulators; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D018715:Microscopy, Video; D016297:Mutagenesis, Site-Directed; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D014162:Transfection; D020764:cdc42 GTP-Binding Protein; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae; D020741:rho GTP-Binding Proteins
chemical_list: D001798:Blood Proteins; C422984:CDC42EP2 protein, human; C422985:CDC42EP4 protein, human; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D020549:GTP Phosphohydrolase Activators; D020555:GTP-Binding Protein Regulators; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D006160:Guanosine Triphosphate; D005982:Glutathione Transferase; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae; D020741:rho GTP-Binding Proteins