Cell biology: A sensor for calcium uptake

Abstract

Mitochondria — the cell’s power plants — increase their energy production in response to calcium signals in the cytoplasm. A regulator of the elusive mitochondrial calcium channel has now been identified.

Figure 1. Ca²⁺ hotspots

Calcium ions are transferred directly between the endoplasmic reticulum (ER) and mitochondria at junctions between the two organelles. This transfer is mediated by the IP₃ receptor in the ER membrane and the Ca²⁺ uniporter in the inner mitochondrial membrane. Although IP₃ receptors and uniporters are probably distributed all over their respective organelles, uniporters at junctions can be preferentially activated owing to the high local Ca²⁺ concentrations present. Perocchi et al. identify MICU1 as a Ca²⁺-sensitive regulator of the mitochondrial uniporter.