Hic-5, a paxillin homologue, binds to the protein-tyrosine phosphatase PEST (PTP-PEST) through its LIM3 domain

The Hic-5 protein is encoded by a transforming growth factor-beta 1- and hy drogen peroxide-inducible gene, hic-5, and has striking similarity to paxil lin, especially in their C-terminal LIM domains. Like paxillin, Hic-5 is lo calized in focal adhesion plaques in association with focal adhesion kinase in cultured fibroblasts. We carried out yeast two-hybrid screening to iden tify cellular factors that form a complex with Hic-5 using its LIM domains as a bait, and we identified a cytoplasmic tyrosine phosphatase (PTP-PEST) as one of the partners of Hic-5. These two proteins are associated in mamma lian cells. From in vitro binding experiments using deletion and point muta tions, it was demonstrated that the essential domain in Hic-5 for the bindi ng was LIM 3, As for PTP-PEST, one of the five proline-rich sequences found on PTP-PEST, Pro-2, was identified as the binding site for Hic-5 in in vit ro binding assays. Paxillin also binds to the Pro-a domain of PTP-PEST. In conclusion, Hic-5 may participate in the regulation of signaling cascade th rough its interaction with distinct tyrosine kinases and phosphatases.