ASSOCIATION OF HUMAN PROTEIN-TYROSINE-PHOSPHATASE-KAPPA WITH MEMBERS OF THE ARMADILLO FAMILY

We have identified a human receptor-like protein-tyrosine phosphatase (PTP) in the mammary carcinoma cell line SK-BR-3, which represents the human homolog of murine PTP kappa (Jiang, Y.-P., Wang, H., D'Eustachi o, P., Musacchio, J. M., Schlessinger, J., and Sap, J. (1993) Mot. Cel l, Biol, 13, 2942-2951) and was therefore termed hPTP kappa. We show h ere that hPTP kappa expression is dependent on cell density and find i t colocalized with two members of the arm family of proteins, beta-cat enin and gamma-catenin/plakoglobin, at adherens junctions, Using both in vitro and in vivo binding assays, we demonstrate specific complex f ormation between endogenous hPTP kappa and beta- and gamma-catenin/pla koglobin. In addition, we present evidence that suggests that beta-cat enin may represent a substrate for the catalytic activity of hPTP kapp a, The identification of specific binding partners for this receptor-l ike PTP provides insight into the mechanisms of its biological action and suggests a role for hPTP kappa in the regulation of processes invo lving cell contact and adhesion such as growth control, tumor invasion , and metastasis.