| Abstract: | SHP-1 and SHP-2 are intracellular protein tyrosine phosphatases containing two adjacent src homology 2 domains that target these phosphatases to cell surface receptor signaling complexes and play a role in receptor signal transduction. In this report the PC12 cell system was used to investigate the potential roles of SHP-1 and SHP-2 in the induction of neuronal differentiation by nerve growth factor (NGF). By using neurite outgrowth as a marker for differentiation, the effects of transfected constructs of SHP-1 and SHP-2 were assessed. Overexpression of a catalytically inactive SHP-2, but not a catalytically inactive SHP-1, blocked NGF-stimulated neurite outgrowth. The mitogen-activated protein kinase (MAPK) signaling cascade is important for the morphological differentiation in PC12 cells, and both SHP-1 and SHP-2 have been implicated to act upstream of MAPK in other receptor signaling systems. A positive role for SHP-2 but not SHP-1 in the activation of MAPK by NGF was demonstrated by introduction of the SHP-2 phosphatase mutants along with hemagglutinin-tagged MAPK. Coexpression studies with the SHP-2 mutant along with mutant forms of MAPK kinase suggested that SHP-2 functions upstream of MAPK kinase and MAPK in NGF-induced neurite outgrowth. |
