Phosphorylation of Hic-5 at tyrosine 60 by CAKbeta and Fyn.

Hic-5 is a CAKbeta-binding protein localized at focal adhesions. Here we show that overexpression of CAKbeta or Fyn, but not FAK, enhanced the tyrosine phosphorylation of coexpressed Hic-5 in COS-7 cells. These phosphorylations were further augmented by stimulating cells with osmotic stress. The Y60F mutant of Hic-5 was not phosphorylated, and Hic-5 phosphorylated on tyrosine 60 was bound specifically to the SH2 domain of Csk. Coexpression experiments revealed that the phosphorylation of Hic-5 by CAKbeta required the kinase activation of CAKbeta and binding of Hic-5 by CAKbeta. Specific phosphorylation of Hic-5 by CAKbeta and Fyn may activate a signaling pathway mediated by Hic-5.