title: Cdc42 antagonizes inductive action of cAMP on cell shape, via effects of the myotonic dystrophy kinase-related Cdc42-binding kinase (MRCK) on myosin light chain phosphorylation.
abstract: Rho GTPases play pivotal roles in regulating cell morphology. We previously showed that RhoA acts via ROKalpha to counteract the effects of the classical second messenger cyclic AMP on cell shape changes. Here we show that active Cdc42V12 also competes against the cAMP-induced stellate morphology in SH-EP cells. This Cdc42 effect is not mediated by the RhoA/ ROK pathway but rather the related MRCKalpha, a myotonic dystrophy kinase-related Cdc42-binding kinase. Co-expression of a dominant inhibitory MRCKalpha mutant with Cdc42V12 blocks the ability of the GTPase to counteract cAMP, suggesting that MRCK acts downstream of Cdc42 in this process. Cdc42V12 enhances the phosphorylation of myosin light chain (MLC) at the cell periphery and sustains focal adhesion complexes, while MLC kinase inhibitors destroy focal adhesion complexes and impair the Cdc42V12 protective effect. The data suggest that the maintenance of focal adhesion complexes via the regulation of myosin II activity underlies the ability of Cdc42 to protect against the effect of elevated cAMP.
authors.affiliation: Glaxo-IMCB Group, Institute of Molecular and Cell Biology, Singapore. mcbdjm@imcb.nus.edu.sg
authors.forename: Jing-Ming
authors.initials: JM
authors.lastname: Dong
authors.forename: Thomas
authors.initials: T
authors.lastname: Leung
authors.forename: Edward
authors.initials: E
authors.lastname: Manser
authors.forename: Louis
authors.initials: L
authors.lastname: Lim
mesh_terms: D036002:ADP Ribose Transferases / Q000378:metabolism; D000818:Animals; D001905:Botulinum Toxins / Q000378:metabolism; D002460:Cell Line; D048429:Cell Size; D005576:Colforsin / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D022001:Focal Adhesions / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008845:Microinjections; D009154:Mutation; D018994:Myosin Light Chains / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
chemical_list: D018994:Myosin Light Chains; D011993:Recombinant Fusion Proteins; D005576:Colforsin; D000242:Cyclic AMP; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D017346:Protein Serine-Threonine Kinases; D009219:Myosin-Light-Chain Kinase; D001905:Botulinum Toxins; D020764:cdc42 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein