CHROMOGRANIN A RELATED PEPTIDES IN THE GUT AND PANCREAS

嗜铬粒蛋白A(CgA)是一种分泌型糖蛋白，几乎在所有 内分泌-神经内分泌细胞。CGA通常与共存存储在一起 分泌颗粒中的多肽，其内容物被释放以响应 对外界的刺激。尽管确切的生理意义 关于CGA的问题仍然是一个谜，已经提出了几个想法。其中一个建议 CgA是一种较小的、具有生物活性的前体(即前激素) 多肽。例如，胰抑素是CGA加工的产物， 发现于胰腺和胃肠道的肠内分泌细胞。 胰腺抑素是一种有效的胰岛素分泌抑制剂。在内分泌方面- 神经内分泌细胞，CGA转化为胰腺抑素的可能性 涉及CGA在单个或成对的碱性氨基酸上的切割 内切蛋白水解酶。直到最近才发现了一些内切酶 (也称为前激素转换酶[PC])已被鉴定。我们打算 检查PC-1和PC-2这两台特定PC在 CGA转化为胰岛抑素的工艺研究。关于CGA的另一种假设 函数表明它与存储和处理 多肽被指定为受调节的分泌途径；因此，我们将 检测CGA及其共驻留肽的动态平衡调节。 胃肽、胃泌素伴随基因的基因表达 CgA在人卵巢腺癌细胞系中的表达 钙调节肽，甲状旁腺激素相关肽(PTHrP)， 由人肝细胞系合成并释放。我们打算 检查CgA及其共存的多肽是否表现出 调节分泌，如果CGA在这些细胞中被加工成胰抑素 细胞系。这项研究提案的工作假设包括： 嗜铬粒蛋白A(CGA)是生物活性多肽的前体 在胃肠道(GI)的肠内分泌细胞和 胰腺；前激素转换酶(PC)参与这一过程 CG对其产物胰岛抑素的作用；CgA及其受体的细胞内稳态 共存的多肽是相连的；而胃泌素的产生和分泌- 胰腺癌、结肠癌和卵巢癌细胞株中的相关多肽，以及 甲状旁腺激素相关肽(PTHrP)在肝细胞系中的表达 由CGA陪同。这项建议的具体目的是：1) 胰腺和胰腺中胰岛抑素样多肽的特征 胃肠道，2)检查前激素的参与 转化酶PC-1和PC-2在胰腺抑素变异体形成中的作用 从CGA，3)研究CGA及其共居的监管 多肽(即胰岛素)的动态平衡和CGA加工的控制 胰腺内分泌中的胰抑素，4)检验这一假说 CgA与胃泌素多肽共存于胰腺、结肠和 卵巢癌细胞和肝细胞中的甲状旁腺素相关蛋白(Hep-G2)； CgA及其共存的多肽具有调节分泌的特性。

Chromogranin A (CGA) is a secretory glycoprotein identified in nearly all endocrine-neuroendocrine cells. CGA is stored typically with co-resident peptides in secretory granules whose contents are released in response to external stimulation. Although the exact physiological significance of CGA remains an enigma, several ideas have been put forth. One suggests that CGA is a precursor (ie, prohormone) of smaller, biologically active peptides. For instance, pancreastatin, a product of CGA processing, is found in enteroendocrine cells of the pancreas and GI tract. Pancreastatin is a potent inhibitor of insulin secretion. In endocrine- neuroendocrine cells, the conversion of CGA to pancreastatin most likely involves cleavage of CGA at single or paired basic amino acids by endoproteolytic enzymes. Only recently have some of the endoproteases (also called prohormone convertases [PCs]) been identified. We intend to examine the relevance of two specific PCs, PC-1 and PC-2, in the processing of CGA to pancreastatin. Another hypothesis regarding CGA function suggests that it is linked to the storage and processing of peptides destined for the regulated secretory pathway; therefore, we will examine the regulation of homeostasis of CGA and its co-resident peptide. Gene expression of a stomach peptide, gastrin, accompanies gene expression for CGA in a human ovarian adenocarcinoma cell line; and, a calcium regulatory peptide, parathyroid hormone-related peptide PTHrp), is synthesized and released by a human hepatic cell line. We intend to examine whether CGA and its co-resident peptide show characteristics of regulated secretion, and if CGA is processed to pancreastatin in these cell lines. The working hypotheses for this research proposal include: chromogranin A (CGA) serves as precursor for biologically active peptides in enteroendocrine cells of the gastrointestinal (GI) tract and pancreases; prohormone convertases (PCs) participate in the processing of CG to its product, pancreastatin; cellular homeostasis of CGA and its co-resident peptide are linked; and, production and secretion of gastrin- related peptides in pancreatic, colon and ovarian cancer cell lines, and of parathyroid hormone-related peptide (PTHrp in a hepatic cell line are accompanied by CGA. The Specific Aims of this proposal are: 1) to characterize pancreastatin-like peptides in the pancreas and gastrointestinal tract, 2) to examine the involvement of the prohormone convertases, PC-1 and PC-2, in the formation of pancreastatin variants from CGA, 3) to investigate the regulation of CGA and its co-resident peptide (ie, insulin) homeostasis, and the control of CGA processing to pancreastatin in the endocrine pancreas, 4) to examine the hypothesis that CGA co-resides with gastrin peptides in pancreatic, colon and ovarian cancer cells and with PTHrp in liver cells (HEP-G2); and, that CGA and its co-resident peptide show properties of regulated secretion.