Elementary Calcium-Release Units Induced by Inositol Trisphosphate

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Science  13 Jun 1997:
Vol. 276, Issue 5319, pp. 1690-1693
DOI: 10.1126/science.276.5319.1690

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The extent to which inositol 1,4,5-trisphosphate (InsP3)–induced calcium signals are localized is a critical parameter for understanding the mechanism of effector activation. The spatial characteristics of InsP3-mediated calcium signals were determined by targeting a dextran-based calcium indicator to intracellular membranes through the in situ addition of a geranylgeranyl lipid group. Elementary calcium-release events observed with this indicator typically lasted less than 33 milliseconds, had diameters less than 2 micrometers, and were uncoupled from each other by the calcium buffer EGTA. Cellwide calcium transients are likely to result from synchronized triggering of such local release events, suggesting that calcium-dependent effector proteins could be selectively activated by localization near sites of local calcium release.

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