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Initiation of IP(3)-mediated Ca(2+) waves in Xenopus oocytes. EMBO J 1999 Oct 01;18(19):5285-99

Date

10/03/1999

Pubmed ID

10508162

Pubmed Central ID

PMC1171599

DOI

10.1093/emboj/18.19.5285

Scopus ID

2-s2.0-0033215479   114 Citations

Abstract

Inositol (1,4,5)-trisphosphate (IP(3)) evokes Ca(2+) liberation in Xenopus oocytes as elementary events (Ca(2+) puffs) that become coupled to propagate Ca(2+) waves with increasing [IP(3)]. To investigate this transition between local and global Ca(2+) signaling, we developed an optical method for evoking rapid subcellular Ca(2+) elevations, while independently photoreleasing IP(3) and simultaneously recording confocal Ca(2+) images. Focal Ca(2+) elevations triggered waves within 100 ms of photoreleasing IP(3), compared with latencies of seconds following photorelease of IP(3) alone. Wave velocity varied with [IP(3)] but was independent of time after photorelease of IP(3), indicating that delayed wave initiation did not involve slow binding of IP(3) to its receptors. The amount of Ca(2+) required to trigger a wave was approximately 10-fold greater than the average size of puffs, and puffs showed no progressive increase in magnitude before waves initiated. Instead, Ca(2+) puffs contributed to a slow rise in basal free [Ca(2+)], which further increased puff frequency and sensitized IP(3) receptors so that individual events then triggered waves. Because the wave threshold is much greater than the size of the elementary puff, cells can employ both local and global signaling mechanisms, and the summation of stochastic behavior of elementary events allows generation of reproducible periodic waves.

Author List

Marchant J, Callamaras N, Parker I

Author

Jonathan S. Marchant PhD Chair, Professor in the Cell Biology, Neurobiology and Anatomy department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Animals
Calcium
Calcium Channels
Calcium Signaling
Cytoplasm
Cytosol
Inositol 1,4,5-Trisphosphate
Inositol 1,4,5-Trisphosphate Receptors
Oocytes
Receptors, Cytoplasmic and Nuclear
Xenopus
jenkins-FCD Prod-482 91ad8a360b6da540234915ea01ff80e38bfdb40a