Epinephrine increases phosphorylation of MAP-2c in rat pheochromocytoma cells (PC12 cells) via a protein kinase C- And mitogen activated protein kinase-dependent mechanism

Adrenoce/ptors mediate effects of endogenous catecholamines and have been shown to affect the neuronal development. Microtubule-associated protein-2 (MAP-2) is an important cytoskeleton protein whose phosphorylation in response to extracellular signal is involved in the regulation of neurite outgrowth and neuronal plasticity. The present study was designed to determine the effect of activation of adrenoceptor by epinephrine on MAP-2 phosphorylation in differentiation PC12 cells and, if so, to explore the mediating mechanism. We found that epinephrine could significantly increase the phosphorylation of MAP-2c at ser136 in a dose- and time-dependent manner in differentiated PC12 cells as well as microtubule arrays. Differentiated PC12 cells express α_2A-adrenoceptor, whose antagonists could block these mentioned effects of epinephrine, and clonidine which is the agonist of α₂-adrenoceptor could mimic the effect of epinephrine. Moreover phosphorylation of ERK and PKC was induced by epinephrine, and ERK and PKC specific inhibitors concentration-dependently prevented epinephrine-induced phosphorylation of MAP-2c at ser136. In addition, pretreatment of PC12 cells with epinephrine partly inhibited 30 μM nocodazole induced neurites retraction. These findings suggest that epinephrine induces phosphorylation of MAP-2c at ser136 through a α₂-adrenoceptor mediated, ERK/PKC-dependent signaling pathway, which may contribute to the stabilization of neurites.