Mitochondrial Ca2+ channels: Great unknowns with important functions

Mitochondria process local and global Ca2+ signals. Thereby the spatiotemporal patterns of mitochondrial Ca2+ signals determine whether the metabolism of these organelles is adjusted or cell death is executed. Mitochondrial Ca2+ channels of the inner mitochondrial membrane (IMM) actually implement mitochondrial uptake from cytosolic Ca2+ rises. Despite great efforts in the past, the identity of mitochondrial Ca2+ channels is still elusive. Numerous studies aimed to characterize mitochondrial Ca2+ uniport channels and provided a detailed profile of these great unknowns with important functions. This mini-review revisits previous research on the mechanisms of mitochondrial Ca2+ uptake and aligns them with most recent findings.