VASOACTIVE-INTESTINAL-PEPTIDE INDUCES DIFFERENTIATION AND MAP KINASE ACTIVATION IN PC12H CELLS

Vasoactive intestinal peptide (VIP), a neuropeptide coupled with adeny late cyclase, was found to induce neurite extension of PC12h cells. Ne urites appeared within 1 h after addition of VIP and extended for at l east 24 h. The half-maximal concentration for the effect of VIP was 50 nM. In addition to the morphological change, VIP induced expression o f VGF protein, a neuron-specific protein associated with neuronal diff erentiation. Western blotting with anti-phosphotyrosine antibody showe d that VIP stimulated tyrosine phosphorylation of two proteins of 42 a nd 44 kDa, which may be two isoforms of MAP kinase, erk1 and erk2. Act ivation of MAP kinases was confirmed by ion-exchange chromatography on a Mono Q column, from which VIP-induced kinase activity was co-eluted with MAP kinase-immunoreactivity. Tyrosine-phosphorylation of MAP kin ases was also stimulated by forskolin or dibutyryl cAMP, indicating th at activation of MAP kinases by VIP might be mediated by cAMP. These r esults suggest that VIP-induced differentiation of PC12 cells is assoc iated with cAMP-dependent activation of MAP kinases.