Rapid activation of p38 mitogen-activated protein kinase by corticosterone in PC12 cells.

The present study using immunoblot showed that corticosterone (B) could induce a rapid activation of p38 in PC12 cells. The dose and time response curves w ere bell shaped with a maximal activation at 10-9 mol/L and 15 min respectively. The activation was not affected by steroid nuclear receptor antagonist RU38486. Bovine serum albumin coupled B (B-BSA) could induce phosphorylation of p38. Tyrosine kinase inhibitor genistein failed to block the phosphorylation, a fact suggesting that the tyrosine kinase activity is not involved in the pathway. On the other hand, phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, could mimic the actions of B, while G 6976, a PKC inhibitor, could completely abolish the phosphorylation induced by B. These results clearly demonstrate that B activates p38 MAPK readily via a putative membrane receptor through a PKC-dependent pathway.