MEK mediates v-Src-induced disruption of the actin cytoskeleton via inactivation of the Rho-ROCK-LIM kinase pathway.
Cellular transformation by v-Src is believed to be caused by aberrant activation of signaling pathways that are normally regulated by cellular Src. Using normal rat kidney cells expressing a temperature-sensitive mutant of v-Src, we examined the role of the Raf/MEK/ERK, phosphatidylinositol 3-kinase/Akt, and Rho pathways in morphological transformation and cytoskeletal changes induced by v-Src. Activation of v-Src elicited a loss of actin stress fibers and focal contacts. A decrease in the phosphorylation level of cofilin was detected upon v-Src activation, which is indicative of attenuated Rho function. Inhibition of MEK using U0126 prevented v-Src-induced disruption of the cytoskeleton as well as dephosphorylation of cofilin, whereas treatment with a phosphatidylinositol 3-kinase inhibitor had no protective effect. In normal rat kidney cells stably transformed by v-Src, we found that the chronic activation of MEK induces down-regulation of ROCK expression, thereby uncoupling Rho from stress fiber formation. Taken together, these results establish MEK as an effector of v-Src-induced cytoskeleton disruption, participating in v-Src-induced antagonism of the cellular function of Rho.
Pawlak
Geraldine
G
Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
Helfman
David M
DM
D000199:Actins / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D002070:Butadienes / Q000494:pharmacology; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D007668:Kidney / Q000166:cytology; D054461:Lim Kinases; D008856:Microscopy, Fluorescence; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D009570:Nitriles / Q000494:pharmacology; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism*; D010641:Phenotype; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction; D013696:Temperature; D013997:Time Factors; D014162:Transfection; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D054460:rho-Associated Kinases
D000199:Actins; D002070:Butadienes; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D009570:Nitriles; C113580:U 0126; D006160:Guanosine Triphosphate; D011494:Protein Kinases; D015688:Oncogene Protein pp60(v-src); D054461:Lim Kinases; C515894:Limk1 protein, rat; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D020741:rho GTP-Binding Proteins