ASSOCIATION OF PTP-PEST WITH THE SH3 DOMAIN OF P130(CAS) - A NOVEL MECHANISM OF PROTEIN-TYROSINE-PHOSPHATASE SUBSTRATE RECOGNITION

The protein tyrosine phosphatase PTP-PEST displays remarkable substrat e specificity, in vitro and in vivo for p130(cas) a signalling interme diate implicated in mitogenic signalling, cell-adhesion induced signal ling, and in transformation by a variety of oncogenes. We have identif ied a high affinity interaction between the SH3 domain of p130(cas) an d a proline-rich sequence ((PPPKPPR)-P-335) within the C-terminal segm ent of PTP-PEST. Mutation of proline 337 within this sequence to alani ne significantly impairs the ability of PTP-PEST to recognise tyrosine phosphorylated p130(cas) as a substrate, without qualitatively affect ing the selectivity of the interaction. Thus the highly specific natur e of the interaction between PTP-PEST and p130(cas) appears to result from a combination of two distinct substrate recognition mechanisms; t he catalytic domain of PTP-PEST contributes specificity to the interac tion with p130(cas), whereas the SH3 domain-mediated association of p1 30(cas) and PTP-PEST dramatically increases the efficiency of the inte raction. Furthermore, our results indicate that one important function of the p130(cas) SH3 domain is to associate with PTP-PEST and thereby facilitate the dephosphorylation of p130(cas), resulting in the termi nation of tyrosine phosphorylation-dependent signalling events downstr eam of p130(cas).