This project includes several studies on the genetic regulation of biosynthesis 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 neurotransmitter in the central and peripheral nervous systems. We previously found that increases in NPY gene transcription rates in PC12 rat pheochromocytoma cell are elicited by synergistic activations of cyclic AMP-dependent protein kinase (PKA) and protein kinase (PKC) and by nerve growth factor (NGF). Using the technique of transient expression of chimeric plasmids, in which a reporter gene is controlled by the rat NPY gene's promoter and 5""""""""- flanking sequence, we obtained evidence suggesting that the PKA/PKC stimulation requires 5'-flanking sequences between bases -2300 and -670. Robust stimulation of the reporter gene by PKA/PKC activation was seen only in cell lines in which the endogenous NPY gene is normally expressed, suggesting involvement of neural crest cell-type-specific element(s) and factor(s), which we are currently attempting to define. Other studies concern the regulation of transcription of the gene coding for proenkephalin, the precursor of the enkephalin opioid peptides. The mechanisms of positive regulation of this gene by (1) glucocorticoids in synergy with cyclic AMP and (2) cell type are under investigation. Evidence has been obtained for the """"""""silencing"""""""" of the proenkephalin gene in non-proenkephalin-producing cell types. In another study, the transactivator protein tax1 of the human T-cell leukemia virus I (HTLV- I) was found to activate the proenkephalin gene promoter in cultured cell systems, a finding that suggests that proenkephalin biosynthesis may be activated in some cells of patients with diseases caused by HTLV-I infection, such as tropical spastic paraparesis. These studies will hopefully shed light on the control of biosynthesis of peptides that are important in autonomic regulation, pain perception, and cognitive function.
