NERVE GROWTH-FACTOR STIMULATES TYROSINE PHOSPHORYLATION AND ACTIVATION OF SRC HOMOLOGY-CONTAINING PROTEIN-TYROSINE-PHOSPHATASE-1 IN PC12 CELLS

Rat PC12 cells respond to extracellular peptide growth factors in at least two distinct ways, When treated with nerve growth factor (NGF) PC12 cells exit the cell cycle and differentiate to a neuronal phenotype, whereas when treated with epidermal growth factor, they proliferate, We examined the potential role of Src homology 2 (SH2)-containing protein tyrosine phosphatases (PTPs) in the differentiation process, PC12 cells express substantial amounts of both SH-PTP1 and 2. SH-PTP1, but not SH-PTP2, becomes tyrosine phosphorylated following NGF, but not epidermal growth factor treatment, The enzymatic activity of SH-PTP1 toward an exogenous substrate following NGF treatment is increased 2-fold. We found that SH-PTP1 binds to the NGF receptor TrkA in vitro and that anti-TrkA immunoprecipitates have PTP activity. These results show that SH-PTP1 is differentially phosphorylated and activated by NGF in PC12 cells and suggest that this activation may play a role in NGF-induced differentiation.