The atypical Rho GTPase Wrch1 collaborates with the nonreceptor tyrosine kinases Pyk2 and Src in regulating cytoskeletal dynamics.
The Cdc42-like GTPase Wnt responsive Cdc42 homolog 1 (Wrch1) has several atypical features; it has an N-terminal proline-rich extension that confers binding to SH3 domains, and it harbors an extremely high intrinsic nucleotide exchange activity, which overrides the normal GTPase activity. As a result, Wrch1 resides mainly in the active, GTP-loaded conformation under normal cellular conditions. We have previously shown that ectopic expression of Wrch1 in fibroblasts resulted in an altered cell morphology visible as a formation of filopodia, a loss of stress fibers, and a reduction in focal adhesions. Here, we show that Wrch1 binds to the nonreceptor tyrosine kinase Pyk2. The interaction required Wrch1 to be in a GTP conformation and also required an intact N-terminal proline-rich extension as well as an intact effector loop. Wrch1 requires Pyk2 in imposing the cytoskeletal effects, seen as the formation of filopodia, since treatment of cells with a Pyk2-specific small interfering RNA abrogated this response. Interestingly, we found that the presence and activity of Src were needed for the formation of a Wrch1-Pyk2 complex as well as for the Wrch1-induced formation of filopodia. We propose a model in which Pyk2 and Src function to coordinate the Wrch1-dependent effects on cytoskeletal dynamics.
Ruusala
Aino
A
Ludwig Institute for Cancer Research, Biomedical Center, Uppsala University, SE-751 24 Uppsala, Sweden.
Aspenström
Pontus
P
D000818:Animals; D001011:Aorta / Q000166:cytology; D002460:Cell Line; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000502:physiology*; D042783:Endothelial Cells / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D051418:Focal Adhesion Kinase 2 / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007668:Kidney / Q000166:cytology; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D010957:Plasmids; D011247:Pregnancy; D011487:Protein Conformation; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism*; D011554:Pseudopodia / Q000502:physiology; D034741:RNA, Small Interfering / Q000494:pharmacology; D013552:Swine; D014162:Transfection; D020798:Two-Hybrid System Techniques; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
D034741:RNA, Small Interfering; D051418:Focal Adhesion Kinase 2; D016392:Proto-Oncogene Proteins pp60(c-src); D020764:cdc42 GTP-Binding Protein