Direct Association of Protein-tyrosine Phosphatase PTP-PEST with Paxillin

Yu Shen,Galen Schneider,Jean-François Cloutier,André Veillette,Michael D Schaller

doi:10.1074/jbc.273.11.6474

Abstract

Tyrosine phosphorylation of focal adhesion-associated proteins may be involved in the regulation of the cytoskeleton and in the control of signals for growth and survival. The focal adhesion kinase (FAK) functions in regulating tyrosine phosphorylation of several of these proteins, including paxillin, tensin, and p130(cas). Protein- tyrosine phosphatases, the counterparts of protein-tyrosine kinases, also presumably regulate phosphorylation of these proteins. We have tested the hypothesis that FAK intimately associates with a protein-tyrosine phosphatase. Protein-tyrosine phosphatase activity associated with the recombinant C-terminal domain of FAK in vitro and could be coimmunoprecipitated with both FAK and paxillin from lysates of chicken embryo cells. However, the interaction with FAK appeared to be indirect and mediated via paxillin. The protein-tyrosine phosphatase was subsequently identified as protein-tyrosine phosphatase-PEST, a nonreceptor protein-tyrosine phosphatase. The C-terminal noncatalytic domain of protein-tyrosine phosphatase-PEST directly bound to paxillin in vitro. The association of both a protein-tyrosine kinase and a protein-tyrosine phosphatase with paxillin suggests that paxillin may play a critical role in the regulation of the phosphotyrosine content of proteins in focal adhesions.

Highlights

The integrins were originally identified as cell surface receptors for extracellular matrix proteins
Association of PTPase Activity with focal adhesion kinase (FAK) in Vitro—Overexpression of FAK in Chicken embryo (CE) cells does not induce tyrosine phosphorylation of cellular proteins unless the cells are treated with vanadate, a PTPase inhibitor [22]
These results suggest that tyrosine phosphorylation of focal adhesion proteins may be controlled by both FAK and an antagonistic, perhaps intimately associated PTPase

Summary

Introduction

The integrins were originally identified as cell surface receptors for extracellular matrix proteins They participate in a variety of cellular events, including adhesion, migration, invasion, cytoskeleton organization, and the generation of cytoplasmic signals [1,2,3]. P130cas and paxillin are, potentially, downstream components of FAK signaling They are colocalized with FAK in focal adhesions, associate with FAK, and become tyrosine-phosphorylated in coordination with FAK [9, 15,16,17,18,19,20]. Tyrosine phosphorylation of p130cas and paxillin by FAK and/or Src-like PTKs likely regulates the assembly of signaling complexes in focal adhesions [13, 21,22,23]. Several candidate PTPases that may be involved in regulating tyrosine phosphorylation in focal adhesions have been identified; they include LAR, PTP1B, and PTP-PEST. Three cellular PTPases and one bacterial PTPase have been implicated as potential regulators of tyrosine phosphorylation of focal adhesion proteins

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Conclusion