Mitochondrial calcium transport: mechanisms and functions

Ca2+ transport across the mitochondrial inner membrane is facilitated by transporters having four distinct sets of characteristics as well as through the Ca2+-induced mitochondrial permeability transition pore (PTP). There are two modes of inward transport, referred to as the Ca2+ uniporter and the rapid mode or RaM. There are also two distinct mechanisms mediating outward transport, which are not associated with the PTP referred to as the Na+-dependent and the Na+-independent Ca2+ efflux mechanisms. Several important functions have been proposed for these mechanisms, including control of the metabolic rate for cellular energy (ATP) production, modulation of the amplitude and shape of cytosolic Ca2+ transients, and induction of apoptosis through release of cytochrome c from the mitochondrial inter membrane space into the cytosolic space. The goals of this review are to survey the literature describing the characteristics of the mechanisms of mitochondrial Ca2+ transport and their proposed physiological functions, emphasizing the more recent contributions, and to consider how the observed characteristics of the mitochondrial Ca2+ transport mechanisms affect our understanding of their functions. (C) 2000 Harcourt Publishers Ltd.