title: Wrch1 is a GTPase-deficient Cdc42-like protein with unusual binding characteristics and cellular effects.
abstract: The Rho family of small GTPases controls many biological processes, including cytoskeletal regulation, membrane trafficking, cell adhesion, cell polarization, transcriptional activity, apoptosis, and cell proliferation. Wrch1, which belongs to the Cdc42 subfamily, is one of the least characterized family member. Despite its homology to other Cdc42-like proteins, we found that Wrch1 has unique characteristics. Biochemical experiments showed that Wrch1 has no detectable GTPase activity in vitro and that its intrinsic nucleotide exchange rate is very high in comparison to Cdc42. Furthermore, NIH3T3 cells transiently transfected with Wrch1 showed an up-rounded, retracted phenotype. In addition, Wrch1 was shown to be more efficient than Cdc42 in triggering the formation of filopodia. Serum stimulation of cells expressing Wrch1 induces vigorous membrane blebbing, a phenomenon dependent on the activity of ROCK. In a search for proteins interacting with Wrch1, PAK1 and NCKbeta were identified as binding partners. Interestingly, the interaction to NCKbeta was shown to be mediated via PxxP motifs present in an N-terminal extension of Wrch1 to the second and third SH3 domains of NCKbeta.
authors.affiliation: Ludwig Institute for Cancer Research, Biomedical Center, S-75124 Uppsala, Sweden.
authors.forename: Jan
authors.initials: J
authors.lastname: Saras
authors.forename: Patrick
authors.initials: P
authors.lastname: Wollberg
authors.forename: Pontus
authors.initials: P
authors.lastname: Aspenström
mesh_terms: D016475:3T3 Cells; D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000077214:Becaplermin; D019556:COS Cells; D002352:Carrier Proteins / Q000378:metabolism*; D002448:Cell Adhesion; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000172:deficiency*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D015513:Oncogene Proteins / Q000378:metabolism*; D010641:Phenotype; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D020574:Proto-Oncogene Proteins c-sis; D011554:Pseudopodia / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D054462:p21-Activated Kinases; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D054460:rho-Associated Kinases; D018909:src Homology Domains / Q000502:physiology
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D016895:Culture Media, Serum-Free; D047908:Intracellular Signaling Peptides and Proteins; C485544:NCK2 protein, human; C117758:Nck2 protein, mouse; D015513:Oncogene Proteins; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D000077214:Becaplermin; C515903:PAK1 protein, human; C515905:Pak1 protein, mouse; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D054460:rho-Associated Kinases; D020558:GTP Phosphohydrolases; C432668:RHOU protein, human; D020764:cdc42 GTP-Binding Protein; D020741:rho GTP-Binding Proteins