Modulation of secretion by dopamine involves decreases in calcium and nicotinic currents in bovine chromaffin cells.

Chromostatin is a 20-residue peptide derived from chromogranin A (CGA), the major soluble component of secretory granules in adrenal meduliary chromaffin cells. One known biological function of chromostatin is to inhibit the secretagogue-evoked catecholamine secretion from chromaffin cells. Putative receptors are present on the chromaffin-cell plasma membrane, and the activation of such receptors leads to the inhibition of L-type voltage-sensitive calcium channels.We report here that exposure of chromaffin cells to chromostatin modifies neither cAMP and cGMP levels nor protein CGA remains the topic of many unanswered questions concerning its possible functions, although recent data suggest a possible prohormonal role in the autocrine and/or paracrine modulation ofregulated secretion. The sequence of pancreastatin, a 49-residue peptide from porcine pancreas inhibiting insulin secretion from endocrine pancreatic islets (2, 3), amylase release from exocrine pancreas (4), and acid secretion from parietal cells (5), is fully contained within the sequence of porcine CGA. CGA is also the precursor of chromostatin, a peptide that exerts a negative-feedback control on the secretory activity of chromaffin cells (6, 7). In addition, an inhibitory autocrine role of CGA on proopiomelanocortin secretion (8) and a regulatory role of aminoterminal CGA-derived peptides on the secretion of calcitonin gene-regulating products (9) and on vascular contractile responses (10) have been reported. Together these observations strongly support the view that CGA is a prohormone.In a previous report, we described the purification of two -CGA-derived peptides active on catecholamine secretion from cultured chromaffin cells (7). A corresponding 20-amino acid peptide named chromostatin was synthesized and found to completely inhibit catecholamine secretion in the nanomolar to micromolar range. Bovine chromaffin cells possess specific receptors for chromostatin the activation of which markedly decreases Ca2+ entry through voltage-gated L-type calcium channels (11). The main purpose ofthe present study was to investigate how the inhibitory effect of chromostatin is achieved. We suggest that a protein phosphatase (PPase) may be responsible, at least partially, for the chromostatininduced inhibition of catecholamine release. 45Ca2-Uptake Experiments. 45Ca2+ (13.5 mCi/mg of Ca; CaCl2 salt; New England Nuclear/DuPont; 1 Ci = 37 GBq) influx into cells was measured as described (14, 15). MATERIALS AND METHODSDetermination of PPase Activity. Histone was phosphorylated with cAMP-dependent protein kinase as described by Zwiller et al. (16), and the 32P-phosphorylated histone was recovered according to the procedure reported by Meisler and Langan (17). Chromaffin cells were grown for 3-6 days at a density of 5 x 106 cells on 35-mm-diameter plastic dishes. After extensive washing, cells were incubated for 10 min in Locke's solution in the presence or absence of 100 nM of the indicated peptide. Cells were subsequently scraped off in 5 mM Tris-HCl, ...

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“…45Ca2+ (13.5 mCi/mg of Ca; CaCl2 salt; New England Nuclear/DuPont; 1 Ci = 37 GBq) influx into cells was measured as described (14,15).…”

Section: Methodsmentioning

confidence: 99%

Chromostatin inhibits catecholamine secretion in adrenal chromaffin cells by activating a protein phosphatase.

Galindo¹,

Zwiller²,

Bader³

et al. 1992

Proc. Natl. Acad. Sci. U.S.A.

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“…Two peptides were synthesized: peptide [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], composed of the 20 residues from position 124 to position 143 in the CGA sequence (Ser-5 to Pro-24 in Fig. 2), and peptide II-24, composed of the 24 residues from position 120 to 143 in the CGA sequence.…”

Section: Resultsmentioning

confidence: 99%

“…45Ca2+ (10-40 mCi/mg of Ca; CaC12 salt; Amersham; 1 Ci = 37 GBq) or 22Na+ (32 mCi/mg ofNa; NaCl salt; Amersham) influx into cells was measured as previously described (15,16).…”

Section: Methodsmentioning

confidence: 99%

Chromostatin, a 20-amino acid peptide derived from chromogranin A, inhibits chromaffin cell secretion.

Galindo

Rill

Bader

et al. 1991

Proc. Natl. Acad. Sci. U.S.A.

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103

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Chromogranin A (CGA) is a ubiquitous 48-kDa secretory protein present in adrenal medulla, anterior pituitary, central and peripheral nervous system, endocrine gut, thyroid, parathyroid, and endocrine pancreas. Recently, we have demonstrated that the protein could be a precursor of bioactive peptides capable of modulating catecholamine secretion from cultured adrenal medullary chromaffin cells. Here we cleaved CGA purified from bovine chromaffmn granules with endoproteinase Lys-C, and we isolated and partially sequenced the peptide inhibiting catecholamine secretion from cultured chromaffim cells. A corresponding synthetic peptide composed of the first 20 N-terminal amino acids produced a dose-dependent inhibition in the 10-9 to 10-6 M range (with an ID.5 of 5 nM) of the catecholamine secretion evoked by carbamoylcholine or by potassium at a depolarizing concentration. This peptide affected secretagogue-induced calcium fluxes but did not alter sodium fluxes. It was found to increase desensitization of cell responses and to modify the kinetics of catecholamine release. Our results indicate that the peptide is extracellularly generated from CGA by a calcium-dependent proteolytic mechanism. We suggest that this peptide, named chromostatin, may be an endocrine modulator of catecholamine-associated responses.

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“…Chromaffin cells are drastically different, however, because they do not require the opening of Na ϩ for catecholamine release. Rather, direct depolarization of the chromaffin cell can cause release due to opening of VGCCs (16,43). This is an important distinction because it illustrates the different mechanisms in play during high-intensity electrical stimulation and the resulting biphasic release.…”

Section: Discussionmentioning

confidence: 97%

Distinguishing splanchnic nerve and chromaffin cell stimulation in mouse adrenal slices with fast-scan cyclic voltammetry

Walsh¹,

Petrović²,

Wightman

2011

American Journal of Physiology-Cell Physiology

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Electrical stimulation is an indispensible tool in studying electrically excitable tissues in neurobiology and neuroendocrinology. In this work, the consequences of high-intensity electrical stimulation on the release of catecholamines from adrenal gland slices were examined with fast-scan cyclic voltammetry at carbon fiber microelectrodes. A biphasic signal, consisting of a fast and slow phase, was observed when electrical stimulations typically used in tissue slices (10 Hz, 350 μA biphasic, 2.0 ms/phase pulse width) were applied to bipolar tungsten-stimulating electrodes. This signal was found to be stimulation dependent, and the slow phase of the signal was abolished when smaller (≤250 μA) and shorter (1 ms/phase) stimulations were used. The slow phase of the biphasic signal was found to be tetrodotoxin and hexamethonium independent, while the fast phase was greatly reduced using these pharmacological agents. Two different types of calcium responses were observed, where the fast phase was abolished by perfusion with a low-calcium buffer while both the fast and slow phases could be modulated when Ca²(+) was completely excluded from the solution using EGTA. Perfusion with nifedipine resulted in the reduction of the slow catecholamine release to 29% of the original signal, while the fast phase was only decreased to 74% of predrug values. From these results, it was determined that high-intensity stimulations of the adrenal medulla result in depolarizing not only the splanchnic nerves, but also the chromaffin cells themselves resulting in a biphasic catecholamine release.

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Modulation of secretion by dopamine involves decreases in calcium and nicotinic currents in bovine chromaffin cells.

Cited by 29 publications

References 56 publications

Chromostatin inhibits catecholamine secretion in adrenal chromaffin cells by activating a protein phosphatase.

Chromostatin inhibits catecholamine secretion in adrenal chromaffin cells by activating a protein phosphatase.

Chromostatin, a 20-amino acid peptide derived from chromogranin A, inhibits chromaffin cell secretion.

Distinguishing splanchnic nerve and chromaffin cell stimulation in mouse adrenal slices with fast-scan cyclic voltammetry

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