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The Strathprints institutional repository is a digital archive of University of Strathclyde's Open Access research outputs. Strathprints provides access to thousands of Open Access research papers by University of Strathclyde researchers, including by researchers from the Department of Computer & Information Sciences involved in mathematically structured programming, similarity and metric search, computer security, software systems, combinatronics and digital health.

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Origin and mechanisms of Ca2+ waves in smooth muscle as revealed by localized photolysis of caged inositol 1,4,5-trisphosphate

McCarron, J.G. and MacMillan, D. and Bradley, K.N. and Chalmers, S. and Muir, T.C. (2004) Origin and mechanisms of Ca2+ waves in smooth muscle as revealed by localized photolysis of caged inositol 1,4,5-trisphosphate. Journal of Biological Chemistry, 279. pp. 8417-8427. ISSN 1083-351X

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Abstract

The cytosolic Ca2+ concentration ([Ca2+]c) controls diverse cellular events via various Ca2+ signaling patterns; the latter are influenced by the method of cell activation. Here, in single-voltage clamped smooth muscle cells, sarcolemma depolarization generated uniform increases in [Ca2+]c throughout the cell entirely by Ca2+ influx. On the other hand, the Ca2+ signal produced by InsP3-generating agonists was a propagated wave. Using localized uncaged InsP3, the forward movement of the Ca2+ wave arose from Ca2+-induced Ca2+ release at the InsP3 receptor (InsP3R) without ryanodine receptor involvement. The decline in [Ca2+]c (the back of the wave) occurred from a functional compartmentalization of the store, which rendered the site of InsP3-mediated Ca2+ release, and only this site, refractory to the phosphoinositide. The functional compartmentalization arose by a localized feedback deactivation of InsP3 receptors produced by an increased [Ca2+]c rather than a reduced luminal [Ca2+] or an increased cytoplasmic [InsP3]. The deactivation of the InsP3 receptor was delayed in onset, compared with the time of the rise in [Ca2+]c, persisted (>30 s) even when [Ca2+]c had regained resting levels, and was not prevented by kinase or phosphatase inhibitors. Thus different forms of cell activation generate distinct Ca2+ signaling patterns in smooth muscle. Sarcolemma Ca2+ entry increases [Ca2+]c uniformly; agonists activate InsP3R and produce Ca2+ waves. Waves progress by Ca2+-induced Ca2+ release at InsP3R, and persistent Ca2+-dependent inhibition of InsP3R accounts for the decline in [Ca2+]c at the back of the wave.