This project consists of several studies on the molecular genetics of protein precursors of neuropeptides in the mammalian nervous system. One study concerns the regulation of the gene coding for neuropeptide Y (NPY), an important regulator in the central and peripheral nervous systems. The primary structure of the rat NPY precursor contains the NPY sequence and a COOH-terminal peptide sequence separated by a proteolytic processing site. In comparison with the human precursor, the strong evolutionary conservation of both peptide sequences (93-100%) suggests that both peptides are physiologically important. In the rat central nervous system, NPY mRNA (800 bases) is most abundant in the striatum and cortex, followed by hippocampus, hypothalamus, and spinal cord. The rat adrenal, spleen, heart, and lung have significant levels of NPY mRNA. In PC12 rat pheochromocytoma cells, the abundance of PNY mRNA was increased by treatment with glucocorticoids, cAMP elevation, or nerve growth factor. Phorbol esters that activate protein kinase C also elevate NPY mRNA but only when the cAMP level is concomitantly elevated. Thus, the NPY gene is regulated by multiple effectors, some acting cooperatively. A second project concerns regulation of transcription of the gene coding for proenkephalin, the precursor of the opioid peptides methionine- and leucine-enkephalin. Glucocorticoids and cAMP synergistically increase the transcription of the proenkephalin gene and the abundance of proenkephalin mRNA in C6 rat glioma cells. Detailed nuclear run-on transcription experiments demonstrated that glucocorticoids exert a permissive effect on proenkephalin gene transcription by prolonging the transcriptional stimulation elicited by cAMP elevation. These studies shed light on the control of biosynthesis of peptides that are important in autonomic regulation and possibly higher cognitive function.
