Prohormone processing: NPY/Catestatin Peptide Production

神经肽Y （NPY）和catestatin肽由肾上腺髓质染色质细胞和交感神经分泌，调节血压。NPY作为一种直接的血管收缩剂，而catestatin作为一种自分泌调节剂抑制尼古丁刺激的儿茶酚胺释放。原发性高血压患者NPY升高和睾丸素降低暗示它们作为神经效应器参与调节血压。重要的是，了解将激素原前体转化为活性NPY和catestatin的主要蛋白水解酶对于理解控制血压的调节机制至关重要。NPY和catestatin的激素前前体，NPY前体和嗜铬粒蛋白A （CgA）分别在肾上腺髓质分泌囊泡（称为嗜铬粒）内进行蛋白水解加工。我们已经确定了分泌囊组织蛋白酶L，以前被称为？激素原硫醇蛋白酶？（PTP）是前npy和CgA的关键加工酶。此外，本项目还发现了一种抑制分泌囊泡组织蛋白酶l的新型内源性蛇形蛋白内源性肽2 （endopin 2）

Neuropeptide Y (NPY) and catestatin peptides are secreted from adrenomedullary chromaffin cells and sympathetic nerves for the regulation of blood pressure. NPY acts as a direct vasoconstrictor, and catestatin functions as an autocrine regulator to inhibit nicotine-stimulated catecholamine release. Elevated NPY and reduced catestatin in essential hypertension implicate their participation as neuroeffectors in regulating blood pressure. Importantly, knowledge of the major proteolytic enzymes (s) responsible for converting their respective prohormone precursors into active NPY and catestatin is crucial for understanding regulatory mechanisms that control blood pressure. The prohormone precursors of NPY and catestatin, pro-NPY and chromogranin A (CgA), respectively, undergo proteolytic processing within secretory vesicles of adrenal medulla, known as chromaffin granules. We have identified secretory vesicle cathepsin L, previously known as ?prohormone thiol protease? (PTP), as a key processing enzyme for pro-NPY and CgA. Moreover, this project discovered a novel endogenous serpin, endopin 2 that inhibits secretory vesicle cathepsin L. In addition, the subtilisin-like PC1 and PC2 proteases in secretory vesicles may also participate in pro-NPY and CgA processing. Based on these new findings, the goal of Project 3 will be to assess the roles of secretory vesicle cathepsin L and endopin 2, compared to PC1 and PC2, in the production of NPY and catestatin neuropeptides that regulate blood pressure. This project will test the hypothesis that secretory vesicle cathepsin L may be a major processing enzyme for NPY and catestatin, compared to PC1 and PC2 enzymes. Our new results support the emerging biological role of cathepsin L function in secretory vesicles for proteolysis of pro-NPY and CgA. Moreover, our recent studies of cathepsin L knockout mice suggest participation of this protease in NPY production in adrenals. These results lead to the next phase of this study that will (1) evaluate in vitro and cellular processing of pro-NPY and CgA by secretory vesicle cathepsin L, compared to PC1 and PC2, (2) assess the cellular and tissue distribution of cathepsin L and PC enzymes in secretory vesicles that contain NPY and catestatin, (3) conduct cellular antisense and gene knockout studies to examine the relative roles of cathepsin L and PC enzymes for NPY and catestatin production, and (4) evaluate endopin 2 as an endogenous serpin inhibitor of cathepsin L for neuropeptide production. Results will demonstrate the relative roles for cathepsin L and endopin 2, compared to PC1 and PC2, in the biosynthesis of active NPY and catestatin peptide regulators. Project 3 complements the program project theme of understanding the regulation of sympathetic neuroeffectors that participate in blood pressure regulation.