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00925njm 22002777a 4500 dc García-Sancho Martín, Francisco Javier author 2014 Cross-talk between organelles and plasma membrane Ca2+ channels is essential for modulation of the cytosolic Ca2+ ([Ca2+]C) signals, but such modulation may differ among cells. In chromaffin cells Ca2+ entry through voltage-operated channels induces calcium release from the endoplasmic reticulum (ER) that amplifies the signal. [Ca2+]C microdomains as high as 20–50 μM are sensed by subplasmalemmal mitochondria, which accumulate large amounts of Ca2+ through the mitochondrial Ca2+ uniporter (MCU). Mitochondria confine the high-Ca2+ microdomains (HCMDs) to beneath the plasma membrane,where exocytosis of secretory vesicles happens. Cell core [Ca2+]C is much smaller (1–2 μM). By acting as a Ca2+ sink, mitochondria stabilise theHCMDin space and time. In non-excitableHEK293 cells, activation of store-operated Ca2+ entry, triggered by ERCa2+ emptying, also generated subplasmalemmal HCMDs, but, in this case, most of the Ca2+ was taken up by the ER rather than bymitochondria. The smaller size of the [Ca2+]C peak in this case (about 2 μM)may contribute to this outcome, as the sarco-endoplasmic reticulum Ca2+ ATPase has much higher Ca2+ affinity than MCU. It is also possible that the relative positioning of organelles, channels and effectors, as well as cytoskeleton and accessory proteins plays an important role. Journal of Physiology, 2014, p. 261-268 0022-3751 http://uvadoc.uva.es/handle/10324/6348 10.1113/jphysiol.2013.255661 261 268 Journal of Physiology Calcio - Absorción The coupling of plasma membrane calcium entry to calcium uptake by endoplasmic reticulum and mitochondria