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Spatiotemporal patterning of IP 3 ‐mediated Ca 2+ signals in Xenopus oocytes by Ca 2+ ‐binding proteins
Author(s) -
Dargan Sheila L.,
Schwaller Beat,
Parker Ian
Publication year - 2004
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2003.059204
Subject(s) - bapta , biophysics , xenopus , chemistry , microbiology and biotechnology , kinetics , cytosol , parvalbumin , intracellular , biology , biochemistry , neuroscience , physics , quantum mechanics , gene , enzyme
Ca 2+ ‐binding proteins (CaBPs) are expressed in a highly specific manner across many different cell types, yet the physiological basis underlying their selective distribution patterns remains unclear. We used confocal line‐scan microscopy together with photo‐release of IP 3 in Xenopus oocytes to investigate the actions of mobile cytosolic CaBPs on the spatiotemporal properties of IP 3 ‐evoked Ca 2+ signals. Parvalbumin (PV), a CaBP with slow Ca 2+ ‐binding kinetics, shortened the duration of IP 3 ‐evoked Ca 2+ signals and ‘balkanized’ global responses into discrete localized events (puffs). In contrast, calretinin (CR), a presumed fast buffer, prolonged Ca 2+ responses and promoted ‘globalization’ of spatially uniform Ca 2+ signals at high [IP 3 ]. Oocytes loaded with CR or PV showed Ca 2+ puffs following photolysis flashes that were subthreshold in controls, and the spatiotemporal properties of these localized events were differentially modulated by PV and CR. In comparison to results we previously obtained with exogenous Ca 2+ buffers, PV closely mimicked the actions of the slow buffer EGTA, whereas CR showed important differences from the fast buffer BAPTA. Most notably, puffs were never observed after loading BAPTA, and this exogenous buffer did not show the marked sensitization of IP 3 action evident with CR. The ability of Ca 2+ buffers and CaBPs with differing kinetics to fine‐tune both global and local intracellular Ca 2+ signals is likely to have significant physiological implications.