Phosphorylation of Hic‐5 at tyrosine 60 by CAKβ and Fyn

Abstract
Hic‐5 is a CAKβ‐binding protein localized at focal adhesions. Here we show that overexpression of CAKβ 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 CAKβ required the kinase activation of CAKβ and binding of Hic‐5 by CAKβ. Specific phosphorylation of Hic‐5 by CAKβ and Fyn may activate a signaling pathway mediated by Hic‐5.