FUNCTIONAL RELATIONSHIP BETWEEN PTP1B AND SRC ACTIVATION AND LOCALIZATION TO CELL-MATRIX ADHESIONS

ANA E. GONZÁLEZ S. WUSENER, MELISA MONTELEONE AND CARLOS O. ARREGUI.

San Miguel de Tucumán, Tucumán

Congreso; XLV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2009

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

PTP1B is an ER-bound tyrosine phosphatase implicated in the maturation and dynamics of cell-matrix adhesions through Src-dependent pathways. We report a PTP1B-dependent regulation of Src activation and localization to nascent adhesions. PTP1B KO cells (KO) in suspension exhibit basal levels of active Src, which is markedly enhanced by integrin stimulation. In contrast, PTP1B WT (WT) cells show similarly high levels of active Src in either condition. Immunolabeling and FRET analysis reveal that active Src in WT cells shortly plated on fibronectin accumulates in a peripheral ring of nascent adhesions. ER/microtubule dissociation as well as plating on poly-lysine abolishes this distribution, which now remains as a uniform punctate. KO cells plated on fibronectin also show active Src in a uniform punctate. Inactive Src accumulates at the endosome recycling compartment (ERC) in KO cells but distributes uniformly in WT cells. In these cells, expression of a dominant-negative Rab11 (S25N) suppresses active Src localization at nascent adhesions and enhances accumulation of inactive Src at ERC. Complexes of substrate trap PTP1B D181A and Src are visualized in vesicle-like structures using bimolecular fluorescence complementation (BiFC). We conclude that activation and localization of Src at nascent adhesions require the coordinated action of stimulated integrins and PTP1B.Supported by ANPCyT