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. 1997 Aug 15;326(Pt 1):215–220. doi: 10.1042/bj3260215

Incremental Ca2+ mobilization by inositol trisphosphate receptors is unlikely to be mediated by their desensitization or regulation by luminal or cytosolic Ca2+.

M D Beecroft 1, C W Taylor 1
PMCID: PMC1218657  PMID: 9337871

Abstract

The kinetics of Ins(1,4,5)P3 (InsP3)-stimulated Ca2+ release from intracellular stores are unusual in that submaximal concentrations of InsP3 rapidly release only a fraction of the InsP3-sensitive Ca2+ stores. By measuring unidirectional 45Ca2+ efflux from permeabilized rat hepatocytes, we demonstrate that such quantal responses to InsP3 occur at all temperatures between 2 and 37 degrees C, but at much lower rates at the lower temperatures. Preincubation with submaximal concentrations of InsP3, which themselves evoked quantal Ca2+ release, had no effect on the sensitivity of the stores to further additions of InsP3. The final Ca2+ content of the stores was the same whether they were stimulated with two submaximal doses of InsP3 or a single addition of the sum of these doses. Such incremental responses and the persistence of quantal behaviour at 2 degrees C indicate that InsP3-evoked receptor inactivation is unlikely to be the cause of quantal Ca2+ mobilization. Reducing the Ca2+ content of the intracellular stores by up to 45% did not affect their sensitivity to InsP3, but substantially reduced the time taken for each submaximal InsP3 concentration to exert its full effect. These results suggest that neither luminal nor cytosolic Ca2+ regulation of InsP3 receptors are the determinants of quantal behaviour. Our results are not therefore consistent with incremental responses to InsP3 depending on mechanisms involving attenuation of InsP3 receptor function by cytosolic or luminal Ca2+ or by InsP3 binding itself. We conclude that incremental activation of Ca2+ release results from all-or-nothing emptying of stores with heterogeneous sensitivities to InsP3. These characteristics allow rapid graded recruitment of InsP3-sensitive Ca2+ stores as the cytosolic InsP3 concentration increases.

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Selected References

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  1. Berridge M. J. Inositol trisphosphate and calcium signalling. Nature. 1993 Jan 28;361(6410):315–325. doi: 10.1038/361315a0. [DOI] [PubMed] [Google Scholar]
  2. Cheek T. R., Berridge M. J., Moreton R. B., Stauderman K. A., Murawsky M. M., Bootman M. D. Quantal Ca2+ mobilization by ryanodine receptors is due to all-or-none release from functionally discrete intracellular stores. Biochem J. 1994 Aug 1;301(Pt 3):879–883. doi: 10.1042/bj3010879. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Chen S. R., Vaughan D. M., Airey J. A., Coronado R., MacLennan D. H. Functional expression of cDNA encoding the Ca2+ release channel (ryanodine receptor) of rabbit skeletal muscle sarcoplasmic reticulum in COS-1 cells. Biochemistry. 1993 Apr 13;32(14):3743–3753. doi: 10.1021/bi00065a029. [DOI] [PubMed] [Google Scholar]
  4. Combettes L., Cheek T. R., Taylor C. W. Regulation of inositol trisphosphate receptors by luminal Ca2+ contributes to quantal Ca2+ mobilization. EMBO J. 1996 May 1;15(9):2086–2093. [PMC free article] [PubMed] [Google Scholar]
  5. Eberhard M., Erne P. Inositol 1,4,5-trisphosphate-induced calcium release in permeabilized platelets is coupled to hydrolysis of inositol 1,4,5-trisphosphate to inositol 1,4-bisphosphate. Biochem Biophys Res Commun. 1993 Aug 31;195(1):19–24. doi: 10.1006/bbrc.1993.2003. [DOI] [PubMed] [Google Scholar]
  6. Ferris C. D., Cameron A. M., Huganir R. L., Snyder S. H. Quantal calcium release by purified reconstituted inositol 1,4,5-trisphosphate receptors. Nature. 1992 Mar 26;356(6367):350–352. doi: 10.1038/356350a0. [DOI] [PubMed] [Google Scholar]
  7. Galione A. Cyclic ADP-ribose: a new way to control calcium. Science. 1993 Jan 15;259(5093):325–326. doi: 10.1126/science.8380506. [DOI] [PubMed] [Google Scholar]
  8. Hajnóczky G., Thomas A. P. The inositol trisphosphate calcium channel is inactivated by inositol trisphosphate. Nature. 1994 Aug 11;370(6489):474–477. doi: 10.1038/370474a0. [DOI] [PubMed] [Google Scholar]
  9. Hirota J., Michikawa T., Miyawaki A., Furuichi T., Okura I., Mikoshiba K. Kinetics of calcium release by immunoaffinity-purified inositol 1,4,5-trisphosphate receptor in reconstituted lipid vesicles. J Biol Chem. 1995 Aug 11;270(32):19046–19051. doi: 10.1074/jbc.270.32.19046. [DOI] [PubMed] [Google Scholar]
  10. Kindman L. A., Meyer T. Use of intracellular Ca2+ stores from rat basophilic leukemia cells to study the molecular mechanism leading to quantal Ca2+ release by inositol 1,4,5-trisphosphate. Biochemistry. 1993 Feb 9;32(5):1270–1277. doi: 10.1021/bi00056a011. [DOI] [PubMed] [Google Scholar]
  11. Marchant J. S., Chang Y. T., Chung S. K., Irvine R. F., Taylor C. W. Rapid kinetic measurements of 45Ca2+ mobilization reveal that Ins(2,4,5)P3 is a partial agonist at hepatic InsP3 receptors. Biochem J. 1997 Feb 1;321(Pt 3):573–576. doi: 10.1042/bj3210573. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Marshall I. C., Taylor C. W. Biphasic effects of cytosolic Ca2+ on Ins(1,4,5)P3-stimulated Ca2+ mobilization in hepatocytes. J Biol Chem. 1993 Jun 25;268(18):13214–13220. [PubMed] [Google Scholar]
  13. Meyer T., Stryer L. Transient calcium release induced by successive increments of inositol 1,4,5-trisphosphate. Proc Natl Acad Sci U S A. 1990 May;87(10):3841–3845. doi: 10.1073/pnas.87.10.3841. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Missiaen L., De Smedt H., Droogmans G., Casteels R. Ca2+ release induced by inositol 1,4,5-trisphosphate is a steady-state phenomenon controlled by luminal Ca2+ in permeabilized cells. Nature. 1992 Jun 18;357(6379):599–602. doi: 10.1038/357599a0. [DOI] [PubMed] [Google Scholar]
  15. Muallem S., Pandol S. J., Beeker T. G. Hormone-evoked calcium release from intracellular stores is a quantal process. J Biol Chem. 1989 Jan 5;264(1):205–212. [PubMed] [Google Scholar]
  16. Nunn D. L., Taylor C. W. Liver inositol, 1,4,5-trisphosphate-binding sites are the Ca2(+)-mobilizing receptors. Biochem J. 1990 Aug 15;270(1):227–232. doi: 10.1042/bj2700227. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Nunn D. L., Taylor C. W. Luminal Ca2+ increases the sensitivity of Ca2+ stores to inositol 1,4,5-trisphosphate. Mol Pharmacol. 1992 Jan;41(1):115–119. [PubMed] [Google Scholar]
  18. Oldershaw K. A., Nunn D. L., Taylor C. W. Quantal Ca2+ mobilization stimulated by inositol 1,4,5-trisphosphate in permeabilized hepatocytes. Biochem J. 1991 Sep 15;278(Pt 3):705–708. doi: 10.1042/bj2780705. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Parys J. B., Missiaen L., De Smedt H., Casteels R. Loading dependence of inositol 1,4,5-trisphosphate-induced Ca2+ release in the clonal cell line A7r5. Implications for the mechanism of quantal Ca2+ release. J Biol Chem. 1993 Nov 25;268(33):25206–25212. [PubMed] [Google Scholar]
  20. Parys J. B., Missiaen L., Smedt H. D., Sienaert I., Casteels R. Mechanisms responsible for quantal Ca2+ release from inositol trisphosphate-sensitive calcium stores. Pflugers Arch. 1996 Jul;432(3):359–367. doi: 10.1007/s004240050145. [DOI] [PubMed] [Google Scholar]
  21. Patel S., Taylor C. W. Quantal responses to inositol 1,4,5-trisphosphate are not a consequence of Ca2+ regulation of inositol 1,4,5-trisphosphate receptors. Biochem J. 1995 Dec 15;312(Pt 3):789–794. doi: 10.1042/bj3120789. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Renard-Rooney D. C., Hajnóczky G., Seitz M. B., Schneider T. G., Thomas A. P. Imaging of inositol 1,4,5-trisphosphate-induced Ca2+ fluxes in single permeabilized hepatocytes. Demonstration of both quantal and nonquantal patterns of Ca2+ release. J Biol Chem. 1993 Nov 5;268(31):23601–23610. [PubMed] [Google Scholar]
  23. Ribeiro-do-Valle R. M., Poitras M., Boulay G., Guillemette G. The important discrepancy between the apparent affinity observed in Ca2+ mobilization studies and the Kd measured in binding studies is a consequence of the quantal process by which inositol 1,4,5-trisphosphate releases Ca2+ from bovine adrenal cortex microsomes. Cell Calcium. 1994 Jan;15(1):79–88. doi: 10.1016/0143-4160(94)90106-6. [DOI] [PubMed] [Google Scholar]
  24. Swillens S., Combettes L., Champeil P. Transient inositol 1,4,5-trisphosphate-induced Ca2+ release: a model based on regulatory Ca(2+)-binding sites along the permeation pathway. Proc Natl Acad Sci U S A. 1994 Oct 11;91(21):10074–10078. doi: 10.1073/pnas.91.21.10074. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Taylor C. W. Kinetics of inositol 1,4,5-trisphosphate-stimulated Ca2+ mobilization. Adv Second Messenger Phosphoprotein Res. 1992;26:109–142. [PubMed] [Google Scholar]
  26. Taylor C. W., Traynor D. Calcium and inositol trisphosphate receptors. J Membr Biol. 1995 May;145(2):109–118. doi: 10.1007/BF00237369. [DOI] [PubMed] [Google Scholar]
  27. Taylor C. W. Why do hormones stimulate Ca2+ mobilization? Biochem Soc Trans. 1995 Aug;23(3):637–642. doi: 10.1042/bst0230637. [DOI] [PubMed] [Google Scholar]

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