CD44 interaction with c-Src kinase promotes cortactin-mediated cytoskeleton function and hyaluronic acid-dependent ovarian tumor cell migration

In this study we have demonstrated that both CD44 (the hyaluronan (HA) rece ptor) and c-Src kinase are expressed in human ovarian tumor cells (SK-OV-3. ipl cell line), and that these two proteins are physically associated as a complex in vivo. Using a recombinant cytoplasmic domain of CD44 and an in v itro binding assay, we have detected a specific interaction between CD44 an d c-Src kinase, Furthermore, the binding of HA to SK-OV-3.ipl cells promote s c-Src kinase recruitment to CD44 and stimulates c-Src kinase activity, wh ich, in turn, increases tyrosine phosphorylation of the cytoskeletal protei n, cortactin, Subsequently, tyrosine phosphorylation of cortactin attenuate s its ability to cross-link filamentous actin in vitro. In addition, transf ection of SK-OV-3.ipl cells with a dominant active form of c-Src (Y527F)cDN A promotes CD44 and c-Src association with cortactin in membrane projection s, and stimulates HA-dependent/CD44-specific ovarian tumor cell migration. Finally, overexpression of a dominant-negative mutant of c-Src kinase (K295 R) in SK-OV-3.ipl cells impairs the tumor cell-specific phenotype, Taken to gether, these findings strongly suggest that CD44 interaction with c-Src ki nase plays a pivotal role in initiating cortactin-regulated cytoskeleton fu nction and HA-dependent tumor cell migration, which may be required for hum an ovarian cancer progression.