Antisense experiments reveal molecular details on mechanisms of ICER suppressing cAMP-inducible genes in rat pinealocytes

In the rat pineal gland neuronal signals determine the rhythmic synthesis o f the hormone melatonin, Norepinephrine (NE) is the principal neurotransmit ter that drives hormone synthesis by activating the cAMP signaling pathway. This activation depends on transcriptional and posttranscriptional regulat ory mechanisms. The cAMP-dependent transcriptional regulation of the rate-l imiting enzyme of melatonin synthesis, arylalkylamine-N-acetyltransferase ( AA-NAT) involves the activating transcription factor (TF) CREB and the inhi bitory TF ICER. By silencing elements of this cAMP-dependent neuroendocrine transduction cascade we wished to gain further insight into the role of IC ER in the regulation of gene expression in rat pineal gland. Inhibition of specific kinases in primary pinealocyte cultures showed that ICER induction depends pivotally on the activation of cAMP-dependent protein kinase II. E liminating ICER's impact by transfecting antisense constructs into pinealoc ytes revealed a predominant beta-adrenergic mechanism in regulating a cotra nsfected CRE-inducible reporter gene and notably, also the endogenous AA-NA T gene. Deciphering molecular details of the cAMP-dependent gene expression in mammalian pinealocytes provides a basis for understanding the general a rchitecture of this signaling pathway that serves adaptive processes ubiqui tously in the organism.