Secretogranin II: Regulation of Synthesis and Post‐Translational Proteolysis in Bovine Adrenal Chromaffin Cells

Abstract

Secretogranin II (SgII), also called chromogranin C, is an acidic tyrosine-sulfated secretory protein found in secretory granules in a wide variety of endocrine cells and neurones. Although less abundant than chromogranin A (CGA) and chromogranin B (CGB), SgII is found in adrenal medullary chromaffin granules. In the present study we investigated the regulation of SgII biosynthesis in bovine chromaffin cells maintained in primary culture. Cellular proteins were labelled with [35S]methionine and the heat stable chromogranin enriched fraction was isolated. Following electrophoretic separation, the 86 kDa SgII band was identified by sequence analysis using the Edman degradation procedure. The radioactivity incorporated in the 86 kDa SgII band was used as an index of the SgII synthesis rate. We found that stimulation of chromaffin cells with nicotine and histamine and to a smaller extent with angiotensin II and bradykinin significantly enhanced the rate of SgII synthesis. In contrast direct depolarization with K+ may not be sufficient to induce modifications in SgII synthesis suggesting that the raise of cytosolic calcium evoked by high K+ may not be sufficient to induce modifications in SgII synthesis . The possible second messenger pathways involved in the control of SgII biosynthesis were investigated by using protein kinase C and adenylate cyclase activators. We observed that 12-O-tetradecanoylphorbol 13-acetate (TPA) and forskolin increased the basal rate of SgII synthesis. Incubation with both TPA and forskolin was required to obtain an effect comparable to that produced by nicotine or histamine suggesting that these secretagogues recruit both protein kinase C- and cyclic AMP-dependent mechanisms to stimulate SgII synthesis.

Processing of secretogranin II by prohormone convertases: Importance ofPC1 in generation of secretoneurin

“…In the present experiments a putative cleavage of the secretogranin II precursor at sites 7 to 9 was not investigated. In two recent studies, however, peptide fragments resulting from cleavage at sites 8 and 9 were isolated [26,27]. Thus, one can assume that these sites might also be used in vivo by prohormone convertases.…”

Antibacterial and Antifungal Activities of Vasostatin-1, the N-terminal Fragment of Chromogranin A

“…2), we decided to examine the role of the tripeptide Arg 43 -Gly 44 -Asp 45 and the length of the peptidic chain, testing the activities of the synthetic peptides CGA [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60] , CGA , and CGA , respectively (Table III). The comparison of their activity with the activity of CGA [47][48][49][50][51][52][53][54][55][56][57][58][59][60] highlights several important points as follows: (i) CGA 41 ments CGA [47][48][49][50][51][52][53][54][55][56]…”

“…Then, the antifungal properties of the peptides included in the different peaks were tested. An active peptide corresponding to CGA [47][48][49][50][51][52][53][54][55][56][57][58][59][60] with an experimental molecular mass of 1732.9 Da ( Fig. 3B; expected molecular mass, 1733.1 Da) is active against N. crassa showing a minimal inhibitory concentration giving 100% inhibition of 7 M. Incubation of fungi with synthetic peptide corresponding to CGA [47][48][49][50][51][52][53][54][55][56][57][58][59][60] at increasing concentrations from 3 to 10 M (Table III) induces a decrease of fungal proliferation and the inhibition in the growth of filaments.…”

Molecular cloning of frog secretogranin II reveals the occurrence of several highly conserved potential regulatory peptides

“…3 also exhibited a high degree of sequence conservation (68, 70% and 80% identity between the frog and human SglI sequences, respectively). The rat counterpart of peptide number V, named LA-42, has been previously isolated from pituitary gonadotroph-conditioned medium [7] while the bovine counterpart of peptide number VI has been characterized from purified secretory granules of adrenal chromaffin cells [8]. It has also been found that this latter peptide was released from cultured bovine chromaffin cells, together with catecholamines, upon nicotinic stimulation [8].…”

“…The rat counterpart of peptide number V, named LA-42, has been previously isolated from pituitary gonadotroph-conditioned medium [7] while the bovine counterpart of peptide number VI has been characterized from purified secretory granules of adrenal chromaffin cells [8]. It has also been found that this latter peptide was released from cultured bovine chromaffin cells, together with catecholamines, upon nicotinic stimulation [8]. The strong conservation of these four peptides from amphibia to mammals and the fact that three of them have already been characterized in tissue extracts and/or culture media support the concept that SglI may serve as a precursor for several regulatory peptides.…”