Involvement of the Membrane Distal Catalytic Domain in Pervanadate-Induced Tyrosine Phosphorylation of Receptor Protein–Tyrosine Phosphatase α

Abstract

Receptor protein-tyrosine phosphatase α, RPTPα, is a typical transmembrane protein–tyrosine phosphatase (PTP) with two cytoplasmic catalytic domains. RPTPα became strongly phosphorylated on tyrosine upon treatment of cells with the PTP inhibitor pervanadate. Surprisingly, mutation of the catalytic site Cys in the membrane distal PTP domain (D2), but not of the membrane proximal PTP domain (D1) that harbors the majority of the PTP activity, almost completely abolished pervanadate-induced tyrosine phosphorylation. Pervanadate-induced RPTPα tyrosine phosphorylation was not restricted to Tyr789, a known phosphorylation site. Cotransfection of wild-type RPTPα did not potentiate tyrosine phosphorylation of inactive RPTPα-C433SC723S, suggesting that RPTPα-mediated activation of kinase(s) does not underlie the observed effects. Mapping experiments indicated that pervanadate-induced tyrosine phosphorylation sites localized predominantly, but not exclusively, to the C-terminus. Our results demonstrate that RPTPα-D2 played a role in pervanadate-induced tyrosine phosphorylation of RPTPα, which may suggest that RPTPα-D2 is involved in protein–protein interactions.