Sustained formation of focal adhesions with paxillin in morphological differentiation of PC12 cells

Differentiation of PC12 cells triggered by nerve growth factor (NGF) is cha racterized by several well-defined events including induction of a set of n euron-specific genes, gain of membrane excitability, and morphological chan ges such as neurite outgrowth, Here we report that K252a, a protein kinase inhibitor, converts the proliferation signal of epidermal growth factor (EG F) into the morphological differentiation signal without inducing the susta ined activation of ERK and the expression of neurofilament. Major effects o f EGF/K252a, found also in the NGF-treated cells, are the sustained mobilit y shift of paxillin in SDS-PAGE and the promoted association of Crk-II with paxillin, These effects explain the prominent and robust development of pe ripheral focal adhesion assembly and stress fiber-like structures observed in the early stages of PC12 cell differentiation. These results suggest a m odel that cytoskeletal reorganization via focal adhesion assembly triggered by NGF provides a signal required for the morphological differentiation of PC12 cells.