Vimentin intermediate filament reorganization by Cdc42: involvement of PAK and p70 S6 kinase.
Rho family GTPases play a major role in actin cytoskeleton reorganization. Recent studies have shown that the activation of Rho family GTPases also induces collapse of the vimentin intermediate filament (IF) network in fibroblasts. Here, we report that Cdc42V12 induces the reorganization of vimentin IFs in Hela cells, and such reorganization is independent of actin and microtubule status. We analyzed the involvement of three serine/threonine kinase effectors, MRCK, PAK and p70 S6K in the Cdc42-induced vimentin reorganization. Surprisingly, the ROK-related MRCK is not involved in this IF reorganization. We detected phosphorylation of vimentin Ser72, a site phosphorylated by PAK, after Cdc42 activation. PAK inhibition partially blocked Cdc42-induced vimentin IF collapse suggesting the involvement of other effectors. We report that p70 S6 kinase (S6K)1 participates in this IF rearrangement since the inhibitor rapamycin or a dominant inhibitory S6K could reduce the Cdc42V12 or bradykinin-induced vimentin collapse. Further, inhibition of PAK and S6K in combination very effectively prevents Cdc42-induced vimentin IF collapse. Conversely, only in combination active PAK and S6K could induce a vimentin IF rearrangement that mimics the Cdc42 effect. Thus, Cdc42-induced vimentin reorganization involves PAK and, in a novel cytoskeletal role, p70 S6K.
Chan
Wing
W
Glaxo-IMCB Group, Institute of Molecular and Cell Biology, Singapore, Singapore. mcbchanw@imcb.nus.edu.sg
Kozma
Robert
R
Yasui
Yoshihiro
Y
Inagaki
Masaki
M
Leung
Thomas
T
Manser
Ed
E
Lim
Louis
L
D016475:3T3 Cells; D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D005057:Eukaryotic Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D055551:HSP27 Heat-Shock Proteins; D006367:HeLa Cells; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007382:Intermediate Filaments / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D051379:Mice; D009154:Mutation / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism*; D014746:Vimentin / Q000187:drug effects / Q000378:metabolism*; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D054462:p21-Activated Kinases
D002352:Carrier Proteins; D055551:HSP27 Heat-Shock Proteins; C442250:HSPB2 protein, human; D006360:Heat-Shock Proteins; C486699:Hspb2 protein, mouse; D011993:Recombinant Fusion Proteins; D014746:Vimentin; C515903:PAK1 protein, human; C515905:Pak1 protein, mouse; D017346:Protein Serine-Threonine Kinases; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D054462:p21-Activated Kinases; D020764:cdc42 GTP-Binding Protein