Activated c-Fms recruits Vav and Rac during CSF-1-induced cytoskeletal remodeling and spreading in osteoclasts.
Colony-stimulating factor-1 (CSF-1) induces osteoclast spreading that requires activation of c-Src and phosphatidyl inositol 3-kinase (PI3-K), both of which are recruited to activated c-Fms, the CSF-1 receptor. The present report provides evidence that the hemopoietic guanine nucleotide exchange factor (GEF), Vav, and its target GTPase, Rac, lie downstream from this initial signaling complex. CSF-1 treatment of osteoclast-like cells induced translocation of Vav to the plasma membrane, an increase in its phosphotyrosine content, and a concomitant decline in the amount of phosphoinositol 4,5-bisphosphate bound to Vav, changes known to induce Vav's GEF activity. CSF-1 induced the association of Vav and Rac and increased Rac's GTPase activity. CSF-1 also induced rapid translocation of Rac to the periphery of spreading neonatal rat osteoclasts where it co-localized primarily with Vav3 and to a lesser extent with Vav1. Wortmannin, an inhibitor of PI3-K, blocked CSF-1-induced Rac translocation and prevented CSF-1-induced spreading and actin reorganization in osteoclasts. CSF-1-induced osteoclast spreading was not significantly reduced in osteoclasts isolated from Vav1 knock-out mice and Vav1 knock-out mice had normal bone density. Microinjection of constitutively active Rac, but not constitutively active Cdc42 or RhoA, induced lamellipodia formation and osteoclast spreading, mimicking the effects of CSF-1. Dominant-negative Rac blocked CSF-1-induced osteoclast spreading, whereas neither dominant-negative Cdc42 nor C3, an inhibitor of RhoA, affected the response to CSF-1. These data demonstrate that Vav and Rac lie downstream from activated PI3-K in CSF-1-treated osteoclasts and that Rac is required for CSF-1-induced cytoskeletal remodeling in these cells.
Sakai
Hiroaki
H
Yale School of Medicine, TAC S-133, PO Box 208020, New Haven, CT 06520-8020, USA. hiro_yale.@yahoo.co.jp
Chen
Yan
Y
Itokawa
Takashi
T
Yu
Kuan-Ping
KP
Zhu
Mei-Ling
ML
Insogna
Karl
K
D000199:Actins / Q000378:metabolism; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D051379:Mice; D008954:Models, Biological; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011485:Protein Binding; D051567:Proto-Oncogene Proteins c-vav / Q000378:metabolism*; D011554:Pseudopodia / Q000187:drug effects; D051381:Rats; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D000077191:Wortmannin; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
D000199:Actins; D000730:Androstadienes; D004791:Enzyme Inhibitors; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051567:Proto-Oncogene Proteins c-vav; D011994:Recombinant Proteins; D016173:Macrophage Colony-Stimulating Factor; D006160:Guanosine Triphosphate; D016186:Receptor, Macrophage Colony-Stimulating Factor; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D000077191:Wortmannin