Chromogranin A / Pancreastatin
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Introduction of Chromogranin A
Chromaffin A (CGA) is an acidic and hydrophilic secretory protein of 48 kD, which is located in the chromaffin granules of neuroendocrine cells. CGA is a family of pheochromoproteins, which exists in all neuroendocrine cells secreting catechol vesicles and was originally found in the secretory granules of adrenal chromaffin granulocytes. In adrenal medulla chromaffin granules, it is co-secreted with catecholamine and calcium. The protein was found in sympathetic nerve endings, myocardium, pancreas, central and peripheral nervous system, intestinal endocrine tissue, thyroid and parathyroid. The proteolysis is tissue specific, and the difference of the breaking site is related to the tissue in which it is located.
Introduction of Pancreastatin
Pancreastatin is a 49 amino acid polypeptide found for the first time in pig pancreas. It is found in many cells of the neuroendocrine system and is produced by the hydrolysis of its precursor ChromoGranin A. It is found in many cells of the neuroendocrine system. Pancreastatin has been localizeded in insulin-containing β cells, glucagon-containing α cells, and ChromoGranin A in most cycles originated from chromaffin tissue, which may be D cells containing somatostatin in islets. Most of the ChromoGranin A in the cycle comes from chromaffin tissue, which is thought to be the main source of circulating trypsin. The level of trypsin in pigs increased by 50% after meal, and the trypsin and insulin were released at the same time. Electrical stimulation of vagus nerve can also stimulate trypsin release, so its regulation also has vagus nerve components. In humans, blood trypsin levels increased after intravenous injection of mixed meals or glucose intake.
Functions
Pancreastatin (PST) is a regulatory peptide with extensive inhibitory effect on secretion, which is derived from chromogranin A (CgA), a glycoprotein existing in the neuroendocrine system. Human CGA contains PST sequence, which has protein hydrolysis sites on both sides. This suggests that human CGA may be the precursor of human trypsin inhibitor molecules, or it may be the precursor of other bioactive peptides that have not yet been identified. PST is a peptide derived from CGA, which can regulate the metabolism of sugar, lipid and protein in rat adipocytes. PST has an overall antiregulatory effect on insulin by activating a specific receptor-effect system (Gaq/11-protein-PLC- IX-PKC classic).
References
- Broedbaek, K., & Hilsted, L. (2016). Chromogranin A as biomarker in diabetes. Biomarkers in medicine, 10(11), 1181-1189.
- Williams, J. A. (2019). Pancreastatin. Pancreapedia: The Exocrine Pancreas Knowledge Base.
- Di Giacinto, P., Rota, F., Rizza, L., Campana, D., Isidori, A., Lania, A., ... & Baldelli, R. (2018). Chromogranin A: from laboratory to clinical aspects of patients with neuroendocrine tumors. International journal of endocrinology, 2018.
