Cbl associates with Pyk2 and Src to regulate Src kinase activity, alpha(v)beta(3) integrin-mediated signaling, cell adhesion, and osteoclast motility

The signaling events downstream of integrins that regulate cell attachment and motility are only partially understood. Using osteoclasts and transfect ed 293 cells, we find that a molecular complex comprising Src, Pyk2, and Cb l functions to regulate cell adhesion and motility. The activation of integ rin alpha (v)beta (3) induces the [Ca2+](i)-dependent phosphorylation of Py k2 Y402, its association with Src SH2, Src activation, and the Src SH3-depe ndent recruitment and phosphorylation of c-Cbl. Furthermore, the PTB domain of Cbl is shown to bind to phosphorylated Tyr-416 in the activation loop o fSrc, the autophosphorylation site of Src, inhibiting Src kinase activity a nd integrin-mediated adhesion. Finally, we show that deletion of c Src or c -Cbl leads to a decrease in osteoclast migration. Thus, binding of a,Ps int egrin induces the formation of a Pyk2/Src/Cbl complex in which Cbl is a key regulator of Src kinase activity and of cell adhesion and migration. These findings may explain the osteopetrotic phenotype in the Src(-/-) mice.