The Human Mitochondrial DNA Depletion Syndrome Gene MPV17 Encodes a Non-selective Channel That Modulates Membrane Potential*

The human MPV17-related mitochondrial DNA depletion syndrome is an inherited autosomal recessive disease caused by mutations in the inner mitochondrial membrane protein MPV17. Although more than 30 MPV17 gene mutations were shown to be associated with mitochondrial DNA depletion syndrome, the function of MPV17 is still unknown. Mice deficient in Mpv17 show signs of premature aging. In the present study, we used electrophysiological measurements with recombinant MPV17 to reveal that this protein forms a non-selective channel with a pore diameter of 1.8 nm and located the channel's selectivity filter. The channel was weakly cation-selective and showed several subconductance states. Voltage-dependent gating of the channel was regulated by redox conditions and pH and was affected also in mutants mimicking a phosphorylated state. Likewise, the mitochondrial membrane potential (Δψm) and the cellular production of reactive oxygen species were higher in embryonic fibroblasts from Mpv17−/− mice. However, despite the elevated Δψm, the Mpv17-deficient mitochondria showed signs of accelerated fission. Together, these observations uncover the role of MPV17 as a Δψm-modulating channel that apparently contributes to mitochondrial homeostasis under different conditions. Background: MPV17 is a mitochondrial inner membrane protein with unknown function. Results: Recombinant human MPV17 shows highly regulated channel-forming activity; the mitochondrial membrane potential and the reactive oxygen species formation were elevated in embryonic fibroblasts from Mpv17−/− mice. Conclusion: MPV17 functions as a non-selective channel modulating the membrane potential to preserve mitochondrial homeostasis. Significance: Our data are important for understanding the role of MPV17 protein under physiological and pathological conditions.