Chromogranin A: Secretion of Processed Products from the Stimulated Retrogradely Perfused Bovine Adrenal Gland

Abstract

Chromogranin A (CGA) is a member of a family of highly acidic proteins co-stored and co-secreted with adrenaline and noradrenaline in the adrenal medulla. A number of biologically active fragments of CGA (CGAFs) have been characterized including a group of small N-terminal fragments collectively named vasostatins due to their vascular inhibitory activity. In the present study, the release of CGAFs, including CGA N-terminal fragments, from the isolated, retrogradely perfused bovine adrenal gland, has been studied under basal conditions and during nerve stimulation and perfusion with acetylcholine. The CGAFs were characterized by SDS-PAGE followed by immunoblotting with antisera to specific sequences within the CGA molecule. Many different CGAFs were released during stimulation of the glands. Antisera to CGA1-40 and CGA44-76 detected a 7 kD protein whose release was increased during stimulation. This component co-migrated with synthetic CGA1-76, was not immunoreactive to antisera to CGA79-113 or CGA124-143, and was seen whether or not the serine protease inhibitor aprotinin was present in the perfusion medium. The release of an approximately 18 kD component, which stained with antisera to CGA1-40, CGA44-76 and CGA79-113, but not to chromostatin (CGA124-143), was also increased during stimulation. Components of 22 kD and larger were detected with antisera to chromostatin, but not with antisera to CGA1-40, CGA44-76 and CGA79-113. Two of these components of 22 to 24 kD were enhanced during nerve stimulation in the presence of aprotinin. The results indicate that processed chromogranin A fragments are secreted from the bovine adrenal medulla during stimulation of chromaffin cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Novel autocrine feedback control of catecholamine release. A discrete chromogranin a fragment is a noncompetitive nicotinic cholinergic antagonist.

“…Proteolysis of chromogranin A takes place both within secretory granules and extracellularly, giving rise to several smaller biologically active peptides such as pancreastatin (which inhibits insulin and parathyroid hormone release [21]), ␤-granin or vasostatin (which inhibits parathyroid hormone release and relaxes vascular smooth muscle [22][23][24][25][26]), and parastatin (which inhibits parathyroid hormone release [27]). An emerging functional pattern is that such chromogranin A fragments may inhibit further hormone release from the endocrine cell of origin, perhaps in autocrine, homeostatic (negative feedback) fashion.…”

“…These peptides include: ( a ) pancreastatin (porcine chromogranin A 240-288 ; 21), originally isolated from porcine pancreas, which inhibits glucose-stimulated insulin release from islet ␤ cells and parathyroid hormone release from chief cells; ( b ) the NH 2 terminus of chromogranin A, termed ␤ -granin (rat chromogranin A 1-114 ; [22][23][24] or vasostatin (human chromogranin A ; 25,26), which inhibits parathyroid hormone release and relaxes vascular smooth muscle; and parastatin (porcine chromogranin A 347-419 ; 27), which inhibits parathyroid hormone release.…”

Phosphorylation and O-Glycosylation Sites of Bovine Chromogranin A from Adrenal Medullary Chromaffin Granules and Their Relationship with Biological Activities

“…results revealed that two of the post-translational modifications on bovine CGA are detected on derived peptides that inhibit hormone and neurotransmitter release: (i) CGA-(1-113) containing phosphorylated Ser 81 corresponds to the vasostatin II sequence (10) and is homologous to pancreatic rat betagranin (9), and (ii) the natural fragment CGA-(347-419) bearing phosphorylated Ser 372 and Ser 376 is parastatin (18). Previously, both CGA and pancreastatin were shown to inhibit low Ca 2ϩ -stimulated parathyroid cell secretion (53,54).…”

“…For example, in the N-terminal domain, a peptide corresponding to the sequence 1-113 has been shown to inhibit hormone secretion in the bovine parathyroid gland (8); a homologous peptide, betagranin, corresponding to the sequence 1-115 has been isolated from rat pancreas, but its function has not yet been defined (9). Vasostatins are peptides containing the N-terminal sequence 1-76/113 (10) and have been found to exhibit vasoinhibitory activity of isolated human blood vessels (11,12). As early as 1988, it was established that CGA is the precursor of a peptide that inhibits the secretory activity of chromaffin cells (13).…”

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.…”