Journal
PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY
Volume 464, Issue 1, Pages 51-62Publisher
SPRINGER HEIDELBERG
DOI: 10.1007/s00424-012-1108-9
Keywords
Mitochondria; Cytosolic Ca2+ signals; Smooth muscle
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Funding
- Wellcome Trust [092292/Z/10/Z]
- British Heart Foundation [PG/11/70/29086]
- British Heart Foundation [PG/11/70/29086] Funding Source: researchfish
- Wellcome Trust [092292/Z/10/Z] Funding Source: Wellcome Trust
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The cytosolic Ca2+ concentration ([Ca2+](c)) controls virtually every activity of smooth muscle, including contraction, migration, transcription, division and apoptosis. These processes may be activated by large (> 10 mu M) amplitude [Ca2+](c) increases, which occur in small restricted regions of the cell or by smaller (< 1 mu M) amplitude changes throughout the bulk cytoplasm. Mitochondria contribute to the regulation of these signals by taking up Ca2+. However, mitochondria's reported low affinity for Ca2+ is thought to require the organelle to be positioned close to ion channels and within a microdomain of high [Ca2+]. In cultured smooth muscle, mitochondria are highly dynamic structures but in native smooth muscle mitochondria are immobile, apparently strategically positioned organelles that regulate the upstroke and amplitude of IP3-evoked Ca2+ signals and IP3 receptor (IP3R) cluster activity. These observations suggest mitochondria are positioned within the high [Ca2+] microdomain arising from an IP3R cluster to exert significant local control of channel activity. On the other hand, neither the upstroke nor amplitude of voltage-dependent Ca2+ entry is modulated by mitochondria; rather, it is the declining phase of the transient that is regulated by the organelle. Control of the declining phase of the transient requires a high mitochondrial affinity for Ca2+ to enable uptake to occur over the normal physiological Ca2+ range (< 1 mu M). Thus, in smooth muscle, mitochondria regulate Ca2+ signals exerting effects over a large range of [Ca2+] (similar to 200 nM to at least tens of micromolar) to provide a wide dynamic range in the control of Ca2+ signals.
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