Protein Tyrosine Phosphatase PTP1B Is Required For P120 Catenin Association With N-Cadherin Precursor And Progress Through The Secretory Pathway.

HERNANDEZ , MV; ARREGUI, CO

San Diego, California

Congreso; 49th Annual meeting of the ASCB; 2009

American Association for Cell Biology

Previous work demonstrates that PTP1B regulates positively N-cadherin-mediated adhesion, a function that implies direct binding of PTP1B to N-cadherin at the cell surface, and dephosphorylation of beta catenin bound to the complex. This event contributes to stabilize N-cadherin-cytoskeletal connections essential for adhesion. Here we report a novel role of PTP1B in N-cadherin precursor trafficking, which does not require previous PTP1B binding, and it is independent of its role in beta catenin dephosphorylation. Indeed, co-localization and co-immunoprecipitation analysis did not show evidence of PTP1B/N-cadherin precursor complexes. N-cadherin precursor mutants which cannot bind PTP1B traffic normally from ER to Golgi. In contrast, PTP1B knockout (KO) cells, or wild type (WT) cells functionally impaired by dominant-negative constructs, show arrest of N-cadherin precursors in a pre-Golgi stage. This defect cannot be attributed to beta catenin dissociation from N-cadherin precursor complexes since similar levels of beta catenin are found in complexes isolated from WT and KO cells. Interestingly, KO cells showed reduced levels of p120 associated to N-cadherin precursor. Moreover, consistent with a direct role of PTP1B in p120 dephosphorylation, phosphotyrosine content of total p120 was significantly enhanced in KO cells. Expression of N-cadherin precursor mutant that cannot bind p120 in WT cells is significantly arrested in a pre-Golgi stage. Also, a significant accumulation of N-cadherin-GFP occurs in CHO-K1 cells co-transfected with small constructs that sequester endogenous p120. Our results suggest that ER-bound PTP1B promotes trafficking of the N-cadherin precursor through a mechanism that requires its association with p120. Work supported by ANPCyT and CONICET.