Evidence for a functional association between phosphatidylinositol 3-kinase and c-src in the spreading response of osteoclasts to colony-stimulating factor-1

Osteoclasts are bone-resorbing cells whose normal function depends in part upon their ability to migrate over the bone surface to initiate new sites o f bone resorption. The growth factor/cytokine, colony-stimulating factor-1 (CSF-1), potently stimulates osteoclast motility, in a c-src-dependent fash ion. The intracellular signaling molecules that participate with c-src in C SF-l-induced remodeling of the osteoclast cytoskeleton have not been identi fied. Here we demonstrate, using. the inhibitors wortmannin acid LY294002, that activation of phosphatidylinositol 3-kinase (PI3-K) is required for CS F-1-induced spreading in osteoclasts. After CSF-1 treatment of osteoclast-l ike cells, PI3-K activity associated with the CSF-1 receptor c-fms, is incr eased, and the 85-kDa regulatory subunit of PI3-K and c-src coimmunoprecipi tate. CSF-1 induces redistribution of PIS-K to the periphery of the cell. T he association between p85 and c-src is due in part to a direct interaction between the proline-rich sequences of p85 and the SH3 domain of c-src. lie vitro, the c-src SH3 domain stimulates PIS-K activity. Taken together, the current data suggest that c-src, via its SH3 domain, may participate in CS F-l-induced activation of PI3-K and that PI3-K and c-src are in the signali ng pathway that subserves CSF-l-induced cytoskeletal changes in osteoclasts .