TY - JOUR
T1 - Oligopeptide inhibitors of metalloendoprotease activity inhibit catecholamine secretion from bovine adrenal chromaffin cells by modulating intracellular calcium homeostasis.
AU - Lelkes, P. I.
AU - Pollard, H. B.
PY - 1987/11/15
Y1 - 1987/11/15
N2 - Synthetic oligopeptide inhibitors of metalloendoprotease activity were found to inhibit catecholamine release from intact bovine adrenal chromaffin cells. The efficiency of these compounds in blocking secretion was dependent on the type and dose of the secretagogues employed. By contrast, catecholamine release from digitonin-permeabilized cells stimulated with micromolar calcium was virtually not affected. Using a different model system mimicking protein-mediated membrane fusion during exocytosis (Bental, M., Lelkes, P.I., Scholma, J., Hoekstra, D., and Wilschut, J. (1984) Biochim. Biophys. Acta 774, 296-300) we found that exposure of chromaffin granules to a genuine metalloendoprotease, thermolysin, impaired their fusion competence with liposomes. The same oligopeptide inhibitors of metalloendoprotease activity that interfered with secretion from the intact cells were also found to cause an increase in 45Ca2+ efflux concomitant with a slight elevation of the free intracellular calcium concentration [( Ca2+]i) to levels not sufficient to elicit secretion. Subsequent stimulation of the cells in the presence of the potent inhibitors resulted in a reduced increase in the cytosolic calcium concentration, as compared to nontreated control cells. The reduction in the secretagogue-evoked rise in [Ca2+]i was also dependent on the time of pretreatment of the cells with the metalloendoprotease inhibitors. Consistently, none of these effects were seen with structurally similar oligopeptides that are not metalloendoprotease substrates/inhibitors. We conclude that potent inhibitors of metalloendoprotease activity and hence, presumably, the enzymes per se modulate stimulus-secretion coupling by interfering with calcium homeostasis rather than directly with membrane fusion.
AB - Synthetic oligopeptide inhibitors of metalloendoprotease activity were found to inhibit catecholamine release from intact bovine adrenal chromaffin cells. The efficiency of these compounds in blocking secretion was dependent on the type and dose of the secretagogues employed. By contrast, catecholamine release from digitonin-permeabilized cells stimulated with micromolar calcium was virtually not affected. Using a different model system mimicking protein-mediated membrane fusion during exocytosis (Bental, M., Lelkes, P.I., Scholma, J., Hoekstra, D., and Wilschut, J. (1984) Biochim. Biophys. Acta 774, 296-300) we found that exposure of chromaffin granules to a genuine metalloendoprotease, thermolysin, impaired their fusion competence with liposomes. The same oligopeptide inhibitors of metalloendoprotease activity that interfered with secretion from the intact cells were also found to cause an increase in 45Ca2+ efflux concomitant with a slight elevation of the free intracellular calcium concentration [( Ca2+]i) to levels not sufficient to elicit secretion. Subsequent stimulation of the cells in the presence of the potent inhibitors resulted in a reduced increase in the cytosolic calcium concentration, as compared to nontreated control cells. The reduction in the secretagogue-evoked rise in [Ca2+]i was also dependent on the time of pretreatment of the cells with the metalloendoprotease inhibitors. Consistently, none of these effects were seen with structurally similar oligopeptides that are not metalloendoprotease substrates/inhibitors. We conclude that potent inhibitors of metalloendoprotease activity and hence, presumably, the enzymes per se modulate stimulus-secretion coupling by interfering with calcium homeostasis rather than directly with membrane fusion.
KW - Adrenal Medulla/metabolism
KW - Animals
KW - Calcium/metabolism
KW - Catecholamines/metabolism
KW - Cattle
KW - Cells, Cultured
KW - Chromaffin Granules/metabolism
KW - Chromaffin System/metabolism
KW - Digitonin/pharmacology
KW - Homeostasis
KW - Metalloendopeptidases/antagonists & inhibitors
KW - Protease Inhibitors/pharmacology
KW - Thermolysin/metabolism
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M3 - Article
C2 - 3680209
SN - 0021-9258
VL - 262
SP - 15496
EP - 15505
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 32
ER -