CHARACTERIZATION OF PCP-2, A NOVEL RECEPTOR PROTEIN-TYROSINE-PHOSPHATASE OF THE MAM DOMAIN FAMILY

DNA sequences encoding a novel member of the receptor protein tyrosine phosphatase (R-PTP) family, termed PCP-2, were identified in a human pancreatic adenocarcinoma cDNA library, Human PCP-2 cDNA predicts a pr otein of 1430 amino acids with a calculated M(r) of 160 kDa, The predi cted PCP-2 enzyme consists of a 740 amino acid extracellular region, a single transmembrane domain, and a 666 amino acid intracellular porti on, The extracellular sequence contains a MAM (meprin/A5/PTP mu) domai n, an immunoglobulin-like domain and four fibronectin type m-like repe ats, suggesting that it is a member of the PTP kappa and PTP mu subfam ily, The intracellular region contains two tandemly-repeated protein t yrosine phosphatase domains, Northern blot analyses revealed a single transcript of 5.5 kilobases, which is expressed at different levels in many human tissues except spleen and placenta, Upon transfection of P CP-2 cDNA into human embryonic kidney fibroblast 293 cells, a protein with an apparent M(r) of 180 000 was detected by immunoblot analysis, This size was reduced to the predicted M(r) upon treatment with endogl ycosidase F, indicating that PCP-2 is glycosylated and, hence, express ed at the cell surface, A potential role of PCP-2 in cell-cell recogni tion and adhesion is supported by its co-localization with cell adhesi on molecules, such as beta-catenin and E-cadherin, at sites of cell-ce ll contact.