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

Hic-5 is a CAK beta-binding protein localized at focal adhesions. Here we show that overexpression of CAK beta 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 CAK beta required the kinase activation of CAK beta and binding of Hic-5 by CAB beta. Specific phosphorylation of Hic-5 by CAK beta and Fyn mag activate a signaling pathway mediated by Hic-5. (C) 2000 Federation of European Biochemical Societies.