The goal of this project is to develop an understanding of the basic regulatory mechanisms in neurons and endocrine cells which secrete peptides, and through this understanding develop novel pharmacotherapeutic approaches and agents to manipulate peptidergic neuronal and endocrine systems. The primary project of the Unit examines the regulation of the biosynthesis of pro-opiomelanocortin (POMC), a prohormone which is post-translationally processed into the secreted peptides ACTH, alpha-MSH and beta-endorphin. These peptide products are active at neuronal receptors which regulate such processes as mood and pain sensation. Our investigations indicate that regulation of POMC gene expression occurs primarily at the transcriptional level. We have found that POMC expression in the anterior pituitary is stimulated primarily via the CRF receptor using adenylate cyclase as an intermediate while the intermediate lobe is under inhibitory control by D-2 receptors which inhibit adenylate cyclase. In addition to the regulation by cAMP, the expression of POMC mRNA is also increased by the stimulation of protein kinase C with phorbol ester. In order to link regulation of the POMC gene to cell surface receptors, we have utilized the second messenger pathways, cAMP-protein kinase A and diacylglycerol-protein kinase C, to identify phosphoproteins which correlate with increases in transcription. We are currently isolating several of these proteins for further analysis. In addition, the Unit is identifying the 5' upstream regulatory regions of the POMC gene and determining the sequences involved in the intracellular regulation of the POMC gene. These studies will identify potential sites for interfering with peptidergic synthesis as a basis for future therapeutic modalities.
