Department of Physiology, University of California, San Francisco, San Francisco, California 94158, USA.
Nat Commun. 2012;3:1317. doi: 10.1038/ncomms2325.
The mitochondrial calcium uniporter is a highly selective channel responsible for mitochondrial Ca(2+) uptake. The mitochondrial calcium uniporter shapes cytosolic Ca(2+) signals, controls mitochondrial ATP production, and is involved in cell death. Here using direct patch-clamp recording from the inner mitochondrial membrane, we compare mitochondrial calcium uniporter activity in mouse heart, skeletal muscle, liver, kidney and brown fat. Surprisingly, heart mitochondria show a dramatically lower mitochondrial calcium uniporter current density than the other tissues studied. Similarly, in Drosophila flight muscle, mitochondrial calcium uniporter activity is barely detectable compared with that in other fly tissues. As mitochondria occupy up to 40% of the cell volume in highly metabolically active heart and flight muscle, low mitochondrial calcium uniporter activity is likely essential to avoid cytosolic Ca(2+) sink due to excessive mitochondrial Ca(2+) uptake. Simultaneously, low mitochondrial calcium uniporter activity may also prevent mitochondrial Ca(2+) overload in such active tissues exposed to frequent cytosolic Ca(2+) activity.
线粒体钙单向转运体是一种高度选择性的通道，负责线粒体钙的摄取。线粒体钙单向转运体塑造细胞质钙信号，控制线粒体 ATP 产生，并参与细胞死亡。在这里，我们使用直接从线粒体内膜进行的膜片钳记录，比较了来自小鼠心脏、骨骼肌、肝脏、肾脏和棕色脂肪的线粒体钙单向转运体的活性。令人惊讶的是，与其他研究的组织相比，心脏线粒体的线粒体钙单向转运体电流密度明显较低。同样，在果蝇飞行肌中，与其他果蝇组织相比，线粒体钙单向转运体的活性几乎检测不到。由于在高度代谢活跃的心脏和飞行肌中，线粒体占据了细胞体积的 40% 以上，因此低的线粒体钙单向转运体活性可能对于避免由于过多的线粒体钙摄取而导致的细胞质钙吸收非常重要。同时，低的线粒体钙单向转运体活性也可能防止在经常受到细胞质钙活动影响的这种活跃组织中发生线粒体钙过载。
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