Calcium mobilization via intracellular ion channels, store organization and mitochondria in smooth muscle

McCarron, John G. and Chalmers, Susan and Wilson, Calum and Sandison, Mairi E. (2016) Calcium mobilization via intracellular ion channels, store organization and mitochondria in smooth muscle. In: Vascular Ion Channels in Physiology and Disease. Springer, Berlin, pp. 233-254. ISBN 978-3-319-29635-7

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    Abstract

    In smooth muscle, Ca2+ release from the internal store into the cytoplasm occurs via inositol trisphosphate (IP3R) and ryanodine receptors (RyR). The internal Ca2+ stores containing IP3R and RyR may be arranged as multiple separate compartments with various IP3R and RyR arrangements, or there may be a single structure containing both receptors. The existence of multiple stores is proposed to explain several physiological responses which include the progression of Ca2+ waves, graded Ca2+ release from the store and various local responses and sensitivities. We suggest that, rather than multiple stores, a single luminally-continuous store exists in which Ca2+ is in free diffusional equilibrium throughout. Regulation of Ca2+ release via IP3R and RyR by the local Ca2+ concentration within the stores explains the apparent existence of multiple stores and physiological processes such as graded Ca2+ release and Ca2+ waves. Close positioning of IP3R on the store with mitochondria or with receptors on the plasma membrane creates ‘IP3 junctions’ to generate local responses on the luminally-continuous store.