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. 1996 Oct 1;496(Pt 1):255–264. doi: 10.1113/jphysiol.1996.sp021682

Ca(2+)- and GTP-dependent exocytosis in mouse pancreatic beta-cells involves both common and distinct steps.

P Proks 1, L Eliasson 1, C Ammälä 1, P Rorsman 1, F M Ashcroft 1
PMCID: PMC1160841  PMID: 8910213

Abstract

1. The effects of GTP and Ca2+ on secretion from single pancreatic beta-cells were studied using capacitance measurements as an indicator of exocytosis. 2. GTP or GTP gamma S produced a concentration-dependent increase in cell capacitance in the absence of intracellular calcium. There was no effect of cyclic AMP or BAPTA an GTP-induced secretion. 3. In the absence of GTP, the relationship between intracellular calcium concentration and the maximum rate of secretion was fitted by the Hill equation with a slope factor of 2.5 and half-maximal activation at 1.6 microM intracellular Ca2+. Similar values were obtained in the presence of GTP gamma S, suggesting GTP does not alter the sensitivity of the secretory machinery to Ca2+. 4. GDP beta S alone had no effect on cell capacitance but caused a dose-dependent inhibition of exocytosis induced by infusion of either GTP gamma S or Ca2+, suggesting both stimuli involve G-protein activation. GDP beta S was without effect on exocytosis evoked by depolarization-mediated Ca2+ entry. 5. The time course of exocytosis following rapid elevation of GTP gamma S by photolysis of a caged precursor was dependent on the intracellular Ca2+ and cyclic AMP concentrations. 6. Our results are interpreted in terms of a model in which the secretory pathways stimulated by Ca2+ and GTP contain both common and separate parts.

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Selected References

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  1. Ammälä C., Ashcroft F. M., Rorsman P. Calcium-independent potentiation of insulin release by cyclic AMP in single beta-cells. Nature. 1993 May 27;363(6427):356–358. doi: 10.1038/363356a0. [DOI] [PubMed] [Google Scholar]
  2. Ammälä C., Eliasson L., Bokvist K., Larsson O., Ashcroft F. M., Rorsman P. Exocytosis elicited by action potentials and voltage-clamp calcium currents in individual mouse pancreatic B-cells. J Physiol. 1993 Dec;472:665–688. doi: 10.1113/jphysiol.1993.sp019966. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Ammälä C., Larsson O., Berggren P. O., Bokvist K., Juntti-Berggren L., Kindmark H., Rorsman P. Inositol trisphosphate-dependent periodic activation of a Ca(2+)-activated K+ conductance in glucose-stimulated pancreatic beta-cells. Nature. 1991 Oct 31;353(6347):849–852. doi: 10.1038/353849a0. [DOI] [PubMed] [Google Scholar]
  4. Bokvist K., Eliasson L., Ammälä C., Renström E., Rorsman P. Co-localization of L-type Ca2+ channels and insulin-containing secretory granules and its significance for the initiation of exocytosis in mouse pancreatic B-cells. EMBO J. 1995 Jan 3;14(1):50–57. doi: 10.1002/j.1460-2075.1995.tb06974.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Burgoyne R. D., Handel S. E. Activation of exocytosis by GTP analogues in adrenal chromaffin cells revealed by patch-clamp capacitance measurement. FEBS Lett. 1994 May 16;344(2-3):139–142. doi: 10.1016/0014-5793(94)00361-0. [DOI] [PubMed] [Google Scholar]
  6. Burgoyne R. D., Morgan A. Regulated exocytosis. Biochem J. 1993 Jul 15;293(Pt 2):305–316. doi: 10.1042/bj2930305. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Coorssen J. R., Haslam R. J. GTP gamma S and phorbol ester act synergistically to stimulate both Ca(2+)-independent secretion and phospholipase D activity in permeabilized human platelets. Inhibition by BAPTA and analogues. FEBS Lett. 1993 Jan 25;316(2):170–174. doi: 10.1016/0014-5793(93)81209-i. [DOI] [PubMed] [Google Scholar]
  8. Dean P. M. Ultrastructural morphometry of the pancreatic -cell. Diabetologia. 1973 Apr;9(2):115–119. doi: 10.1007/BF01230690. [DOI] [PubMed] [Google Scholar]
  9. Dunlop M., Metz S. A. A phospholipase D-like mechanism in pancreatic islet cells: stimulation by calcium ionophore, phorbol ester and sodium fluoride. Biochem Biophys Res Commun. 1989 Sep 15;163(2):922–928. doi: 10.1016/0006-291x(89)92310-3. [DOI] [PubMed] [Google Scholar]
  10. Fischer von Mollard G., Stahl B., Li C., Südhof T. C., Jahn R. Rab proteins in regulated exocytosis. Trends Biochem Sci. 1994 Apr;19(4):164–168. doi: 10.1016/0968-0004(94)90278-x. [DOI] [PubMed] [Google Scholar]
  11. Gillis K. D., Misler S. Enhancers of cytosolic cAMP augment depolarization-induced exocytosis from pancreatic B-cells: evidence for effects distal to Ca2+ entry. Pflugers Arch. 1993 Jul;424(2):195–197. doi: 10.1007/BF00374612. [DOI] [PubMed] [Google Scholar]
  12. Gomperts B. D. GE: a GTP-binding protein mediating exocytosis. Annu Rev Physiol. 1990;52:591–606. doi: 10.1146/annurev.ph.52.030190.003111. [DOI] [PubMed] [Google Scholar]
  13. Lindau M., Gomperts B. D. Techniques and concepts in exocytosis: focus on mast cells. Biochim Biophys Acta. 1991 Dec 12;1071(4):429–471. doi: 10.1016/0304-4157(91)90006-i. [DOI] [PubMed] [Google Scholar]
  14. Meglasson M. D., Nelson J., Nelson D., Erecinska M. Bioenergetic response of pancreatic islets to stimulation by fuel molecules. Metabolism. 1989 Dec;38(12):1188–1195. doi: 10.1016/0026-0495(89)90158-3. [DOI] [PubMed] [Google Scholar]
  15. Metz S. A., Dunlop M. Stimulation of insulin release by phospholipase D. A potential role for endogenous phosphatidic acid in pancreatic islet function. Biochem J. 1990 Sep 1;270(2):427–435. doi: 10.1042/bj2700427. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Neher E., Marty A. Discrete changes of cell membrane capacitance observed under conditions of enhanced secretion in bovine adrenal chromaffin cells. Proc Natl Acad Sci U S A. 1982 Nov;79(21):6712–6716. doi: 10.1073/pnas.79.21.6712. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Neher E., Zucker R. S. Multiple calcium-dependent processes related to secretion in bovine chromaffin cells. Neuron. 1993 Jan;10(1):21–30. doi: 10.1016/0896-6273(93)90238-m. [DOI] [PubMed] [Google Scholar]
  18. Okano K., Monck J. R., Fernandez J. M. GTP gamma S stimulates exocytosis in patch-clamped rat melanotrophs. Neuron. 1993 Jul;11(1):165–172. doi: 10.1016/0896-6273(93)90280-5. [DOI] [PubMed] [Google Scholar]
  19. Regazzi R., Wollheim C. B., Lang J., Theler J. M., Rossetto O., Montecucco C., Sadoul K., Weller U., Palmer M., Thorens B. VAMP-2 and cellubrevin are expressed in pancreatic beta-cells and are essential for Ca(2+)-but not for GTP gamma S-induced insulin secretion. EMBO J. 1995 Jun 15;14(12):2723–2730. doi: 10.1002/j.1460-2075.1995.tb07273.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Renström E., Eliasson L., Bokvist K., Rorsman P. Cooling inhibits exocytosis in single mouse pancreatic B-cells by suppression of granule mobilization. J Physiol. 1996 Jul 1;494(Pt 1):41–52. doi: 10.1113/jphysiol.1996.sp021474. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Vallar L., Biden T. J., Wollheim C. B. Guanine nucleotides induce Ca2+-independent insulin secretion from permeabilized RINm5F cells. J Biol Chem. 1987 Apr 15;262(11):5049–5056. [PubMed] [Google Scholar]
  22. Wollheim C. B., Ullrich S., Meda P., Vallar L. Regulation of exocytosis in electrically permeabilized insulin-secreting cells. Evidence for Ca2+ dependent and independent secretion. Biosci Rep. 1987 May;7(5):443–454. doi: 10.1007/BF01362507. [DOI] [PubMed] [Google Scholar]

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