CREB phosphorylation and melatonin biosynthesis in the rat pineal gland: Involvement of cyclic AMP dependent protein kinase type II

Phosphorylation of cyclic AMP response element binding protein (CREB) at am ino acid serine 133 appears as an important link between the norepinephrine (NE)-induced activation of second messenger systems and the stimulation of melatonin biosynthesis. Here we investigated in the rat pineal gland: 1) t he type of protein kinase that mediates CREB phosphorylation; and 2) its im pact on melatonin biosynthesis. Immunochemical or immunocytochemical demons tration of serine(133)-phosphorylated cyclic AMP regulated element binding protein (pCREB) and radioimmunological detection of melatonin revealed that only cyclic AMP-dependent protein kinase (PKA) inhibitors suppressed NE-in duced CREB phosphorylation and stimulation of melatonin biosynthesis, where as inhibitors of cyclic GMP-dependent protein kinase (PKG). mitogen-activat ed protein kinase kinase, protein kinase C, or calcium-calmodulin-dependent protein kinase (CaMK) were ineffective. Investigations with cyclic AMP-ago nist pairs that selectively activate either PKA type I or II link NE-induce d CREB phosphorylation and stimulation of melatonin biosynthesis to the act ivation of PKA type II. Our data suggest that PKA type II plays an importan t role in the transcriptional control of melatonin biosynthesis in the rat pineal organ.