Parastatin (porcine chromogranin A347-419), a novel chromogranin A-derived peptide, inhibits parathyroid cell secretion.

Abstract

Chromogranin A (CgA), previously referred to as secretory protein-I, is a 50-kilodalton protein present in secretory granules of many endocrine and neuroendocrine cells. In the parathyroid it is present and cosecreted with PTH in response to hypocalcemia. CgA appears to be a precursor of bioactive peptides including pancreastatin, beta-granin, vasostatin, and chromostatin. The presence of several highly conserved pairs of basic amino acids, putative cleavage sites, in the CgA molecule suggests that other yet unidentified bioactive peptides might exist within the molecule. We tested this speculation by subjecting porcine parathyroid CgA to digestion by endoproteinase Lys-C. Resulting CgA-derived peptides were isolated by reverse-phase C18 HPLC and tested for their ability to affect low-Ca2+ stimulated secretion by porcine parathyroid cells. We characterized one peptide, which we named parastatin, that inhibited secretion of both PTH and CgA in a dose-dependent fashion over the range of 0.2-0.6 microM. Parastatin migrated as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an apparent mol wt of 11,000. Edman degradation yielded the sequence L-S-F-R-A-P-A-Y-G-F-R-G-P-G-L corresponding to residues 347-361 of porcine CgA. Amino acid analysis of endoproteinase Lys-C and endoproteinase Asp-N-generated fragments indicated that parastatin corresponds to residues 347-419 of CgA. A synthetic NH2-terminal fragment of rat parastatin corresponding to residues 1-19 was an inhibitory as intact porcine parastatin on parathyroid gland secretion. These results extend the concept that CgA is a precursor of biologically active peptides.

Mechanisms Underlying Neuronal Death Induced by Chromogranin A-activated Microglia

“…In all tissues examined so far, CGA is proteolytically processed into peptides, of which some have defined biological activity (14,20,21). For instance, CGA-derived peptides have been shown to regulate secretion in various endocrine cell types (22)(23)(24) and to modulate adhesion and spreading of fibroblasts (25). CGA and its proteolytic fragments have been found together with ␤-amyloid protein in senile and pre-amyloid plaques (11,(15)(16)(17).…”

Chromogranin A: current status as a precursor for bioactive peptides and a granulogenic/sorting factor in the regulated secretory pathway

“…3). These are (i) the vasostatin/fl-granin peptides, comprising the N-terminal 113 amino acids (flgranin/vasostatin II) of CGA and in some tissues (except in rat) a shorter N-terminal 76-amino acid polypeptide (vasostatin I) [91,103,104], (ii) pancreastatin [21,105], (iii) WE-14 [86,106,107] and (iv) the parastatin/GE-25 peptides [88,108,109]. Each of the peptides above have been demonstrated to exist in endocrine tissues by extraction, isolation, purification and peptide sequencing.…”

“…Each of the peptides above have been demonstrated to exist in endocrine tissues by extraction, isolation, purification and peptide sequencing. The single exception is parastatin, the existence of which is inferred from the presence of a 14 kDa C-terminal CGA fragment generated in rat insulinoma cells, and the biological activity of the parastatin fragment generated by endoproteinase Lys-C digestion of purified CGA [88,108] The processing of CGA seems to occur preferentially at some but not all pairs of basic amino acids, and at some single basic amino acids, at the C-and N-termini of the molecule [27,103,110,111]. The extent of chromogranin A processing is highly tissuedependent: processing appears to be least complete in the adrenal medulla and progressively greater in intestine, stomach, peripheral nerves, and pancreas [27,103,[110][111][112].…”

Targeting Exocytosis: Ins and Outs of the Modulation of Quantal Dopamine Release

“…The effects of the proteolytic cleavage products of granins on catecholamine release are summarized in Table 1, with the CgA and CgB proteolytic cleavage products inhibiting secretion in neuroendocrine cells and noradrenergic neurites [77][78][79][80][81][82]. On the other hand, secretogranin-derived secretoneurin stimulates the release of DA from nigrostriatal neurons [83].…”

“…cytochalasin D, inhibit CgA parastatin phospholipase activation [77] vasostatin phospholipase activation [78] chromostatin inhibition of L-type Ca 2+ channels [80] CgB catestatin nicotinic cholinergic antagonist [81,82] secretogranin secretoneurin G protein-coupled receptor cascade [83] Granins serve as prohormones (first column) for a number of proteolytic cleavage products (second column). These cleavage products exert modulatory effects on exocytosis (third column) through the mechanisms indicated (fourth column).…”