REGULATION OF CREB PHOSPHORYLATION BY CAMP AND CA2-CELLS( IN PAROTID ACINAR)

Since various secretory stimuli regulate not only secretion but also p rotein, RNA, and DNA syntheses in salivary glands, we evaluated the ef fect of secretory stimuli on the phosphorylation state of CREB (cAMP r esponse element-binding protein). Isoproterenol, forskolin, and CPS-cA MP markedly stimulated the phosphorylation of CREB in parotid acinar c ells, and PKA inhibitors H-8 and H-89 dose-dependently inhibited it. I n contrast, carbachol (CCH) and A23187 decreased CREB phosphorylation, but CCH did not decrease it in the absence of extracellular Ca2+. Alt hough protein phosphatase inhibitor calyculin A alone markedly increas ed the phosphorylation, it could not prevent CCH-induced dephosphoryla tion of CREB. CaM kinase IV, a putative protein kinase for CREB in res ponse to Ca2+ elevation, was undetectable in parotid acinar cells.