title: Myosin II directly binds and inhibits Dbl family guanine nucleotide exchange factors: a possible link to Rho family GTPases.
abstract: Cell migration requires the coordinated spatiotemporal regulation of actomyosin contraction and cell protrusion/adhesion. Nonmuscle myosin II (MII) controls Rac1 and Cdc42 activation, and cell protrusion and focal complex formation in migrating cells. However, these mechanisms are poorly understood. Here, we show that MII interacts specifically with multiple Dbl family guanine nucleotide exchange factors (GEFs). Binding is mediated by the conserved tandem Dbl homology-pleckstrin homology module, the catalytic site of these GEFs, with dissociation constants of approximately 0.3 microM. Binding to the GEFs required assembly of the MII into filaments and actin-stimulated ATPase activity. Binding of MII suppressed GEF activity. Accordingly, inhibition of MII ATPase activity caused release of GEFs and activation of Rho GTPases. Depletion of betaPIX GEF in migrating NIH3T3 fibroblasts suppressed lamellipodial protrusions and focal complex formation induced by MII inhibition. The results elucidate a functional link between MII and Rac1/Cdc42 GTPases, which may regulate protrusion/adhesion dynamics in migrating cells.
authors: Department of Biochemistry and Medical Research Center, Chungbuk National University College of Medicine, Cheongju, South Korea.
authors: Chan-Soo
authors: CS
authors: Lee
authors: Chang-Ki
authors: CK
authors: Choi
authors: Eun-Young
authors: EY
authors: Shin
authors: Martin Alexander
authors: MA
authors: Schwartz
authors: Eung-Gook
authors: EG
authors: Kim
mesh_terms: D000205:Actomyosin / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002448:Cell Adhesion; D002465:Cell Movement / Q000502:physiology*; D004789:Enzyme Activation; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D051379:Mice; D024462:Myosin Type II / Q000235:genetics / Q000378:metabolism*; D041681:NIH 3T3 Cells; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C576607:Arhgef7 protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D010982:Platelet-Derived Growth Factor; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D000205:Actomyosin; D024462:Myosin Type II; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins