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‘Quanta’ Ca 2+ release and the control of Ca 2+ entry by inositol phosphates ‐ a possible mechanism
Author(s) -
Irvine R.F.
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)80692-c
Subject(s) - ryanodine receptor , inositol , receptor , biophysics , inositol trisphosphate , intracellular , chemistry , inositol phosphate , mechanism of action , calcium , cytoplasm , binding site , inositol trisphosphate receptor , biochemistry , biology , in vitro , organic chemistry
The release of Ca 2+ from intracellular stores by sub‐optimal doses of inositol trisphosphate has been shown to be dose‐related (‘quantal’), and a simple model is proposed here to account for this phenomenon. It is suggested that there is a regulatory Ca 2+ ‐binding site on, or associated with, the luminal domain of the InsP 3 receptor, which allosterically controls Ca 2+ efflux, and the affinity for Ca 2+ of that site is modulated by InsP 3 binding to the cytoplasmic domain of the receptor; a similar mechanism applied to the ryanodine receptor might also explain some aspects of Ca 2+ ‐induced Ca 2+ release. The stimulated entry of Ca 2+ into a cell which occurs upon activation of inositide‐linked receptors has been variously and confusingly proposed to be regulated by InsP 3 , InsP 4 , and/or a ‘capacitative’ Ca 2+ pool; the mechanism of InsP, receptor action suggested here is shown to lead to a potential reconciliation of all these conflicting proposals.