Inositol 1,4,5-trisphosphate and guanine nucleotides activate calcium release from endoplasmic reticulum via distinct mechanisms

S. H. Chueh, Donald Gill

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Abstract

A sensitive and specific guanine nucleotide regulatory process has recently been shown to rapidly mediate a substantial release of Ca2+ from endoplasmic reticulum within the N1E-115 neuronal cell line (Gill, D.L., Ueda, T., Chueh, S.H., and Noel, M.W. (1986) Nature 320, 461-464). The relationship between this mechanism and Ca2+ efflux mediated by the intracellular regulator inositol 1,4,5-trisphosphate (IP3) has been investigated. Using saponin-permeabilized N1E-115 cells, studies reveal a number of distinctions between the activation of Ca2+ release mediated by GTP and IP3. Thus, the GTP-mediated Ca2+ release process is specifically activated by polyethylene glycol which increases both GTP sensitivity and the extent of GTP-activated Ca2+ release; in contrast, IP3-dependent Ca2+ release is unaffected by polyethylene glycol. The nonhydrolyzable GTP analogue guanosine 5'-O-(3-thio)triphosphate, which completely inhibits GTP-mediated Ca2+ release, does not alter release mediated by IP3. Decreasing the release temperature from 37 to 4°C decreases IP3-activated Ca2+ release by only 20%, whereas the action of GTP on Ca2+ release is abolished at 4° C. Activation of Ca2+ release by IP3 is completely inhibited by increasing free Ca2+ from 0.1 to 10 μM, whereas the fraction of GTP-dependent Ca2+ release (approximately 50% of ionophore-releasable Ca2+) remains unaltered with increasing free Ca2+. These distinctions between IP3- and GTP-mediated Ca2+ release indicate that the two effectors function via distinct mechanisms to activate Ca2+ release; however, they do not preclude the possibility that coupling between the two mechanisms can occur or that a common Ca2+-translocating pathway activated by both effectors exists.

Original languageEnglish (US)
Pages (from-to)13883-13886
Number of pages4
JournalJournal of Biological Chemistry
Volume261
Issue number30
Publication statusPublished - Dec 1 1986

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All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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