Post-translational processing of chromogranin A: differential distribution of phosphorylated variants of pancreastatin and fragments 248–313 and 297–313 in bovine pancreas and ileum

Abstract

Chromogranin A is a secretory protein expressed widely in neuroendocrine cells. It is known to be phosphorylated but the precise sites of phosphorylation are not known. We have isolated, from bovine pancreas and ileum, chromogranin A fragments corresponding to a region giving rise to a biologically active product, pancreastatin. Phosphorylation patterns were determined by fast atom bombardment mass spectrometry and alkaline phosphatase digestion followed by ion-exchange chromatography and radioimmunoassay. In the pancreas, there were unmodified, mono- and di-phosphorylated forms of the fragment chromogranin A(248-313) with Arg and Glu at positions 293 and 301 respectively; in addition, there were small amounts of monophosphorylated peptide with an alternative primary sequence of His and Lys at 293 and 301 respectively. Two products of cleavage, pancreastatin and the fragment 297-313, were also found in unmodified and monophosphorylated forms. In the ileum, peptides with both alternative primary sequences were found, pancreastatin was absent, and phosphorylation was generally less than in the pancreas. Chromogranin A-derived peptides therefore exhibit tissue-specific patterns of phosphorylation and cleavage, and at least two phosphorylation sites occur in the region giving rise to a biologically active product.

Ferric ions inhibit proteolytic processing of progastrin

“…Serine phosphorylation sites are conserved amongst a number of prohormones including the related peptide procholecystokinin (proCCK), chromogranin A, proenkephalin A and proneuropeptide Y [5,16,17,18,19]. In the case of progastrin serine phosphorylation may be biologically important as the phosphorylated Ser 75 lies immediately adjacent to the dibasic cleavage site Arg 73 Arg 74 .…”

Chromogranin A processing and secretion: specific role of endogenous and exogenous prohormone convertases in the regulated secretory pathway.

“…Processing of chromogranin A is tissue-and cell type-specific, varying at different neuroendocrine sites (2,4,5,40). Metz-Boutigue et al (41) determined at least 12 cleavage sites for chromogranin A in bovine adrenal medulla, wherein the protein is cleaved both intra-and extracellularly; 8 of these 12 cleavage sites are at paired basic residues.…”

A Novel Form of Neurotensin Post-translationally Modified by Arginylation

“…Section 1734 solely to indicate this fact. 1 cholecystokinin (16), serine phosphorylation of peptide YY (25), phosphorylation of adrenocorticotrophic hormone (26), and pancreastatin (27). We now describe, in isolation from porcine intestine, the structural and pharmacological characterizations of neurotensin post-translationally decorated with arginine (R-NT; N-(neurotensin-C5-4-yl)arginine)).…”