PTP1B REGULATES THE TRANSIENT ACTIVATION OF SRC IN NASCENT ADHESIONS

GONZáLEZ S. WUSENER AE, BURDISSO J. AND ARREGUI CO.

Potrero de los Funes, San Luis

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2011

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

PTP1B is an ER-bound tyrosine phosphatase implicated in the modulation of cell-matrix adhesion. Here we examined the mechanisms in which PTP1B is involved in this process. Immunofluorescence analysis of cells expressing PTP1B (WT) and plated on fibronectin revealed a transient accumulation of â3 integrin, talin, phosphoactive FAK, phosphoactive Src, and paxillin in nascent adhesions at the cell periphery, which peaks at 5-10 min after plating. In contrast, PTP1B knockout (KO) cells exhibited uniform punctate distribution of these proteins at all times. Maximal Src activation in WT cells at 10 min after plating correlates with strong phosphorylation of paxillin at tyrosine 118. In contrast, Src activation and paxillin phosphorylation are poorly induced in KO cells. Phosphoactive Src accumulation at adhesions requires paxillin, and expression of non phosphorylatable Y118F paxillin in both paxillin- and PTP1B- KO cells rescued active Src at nascent adhesions. Our results are compatible with a model where PTP1B activates Src at adhesions, and subsequently Src phosphorylates paxillin. The transient nature of these events and the requirement of non phosphorylated paxillin for Src activation suggest a negative feedback loop which inactivates Src after paxillin phosphorylation. Supported by CONICET and ANPCyT.