Impaired Cellular Bioenergetics Causes Mitochondrial Calcium Handling Defects in MT-ND5 Mutant Cybrids
Fig 4
ND5 mutant mitochondria have a reduced ability to buffer calcium.
Mitochondrial calcium [Ca2+]m (A) and Δψm (B) were measured concurrently by confocal microscopy using fluo-4 and TMRM in digitonin permeabilized cells. Exogenous calcium was added in sequential aliquots at the concentrations and times indicated (*). Control (CON) cybrid mitochondria were able to buffer more calcium than both ND5 mutant cybrid mitochondria and ρ0 cell mitochondria. Increases in [Ca2+] up to 2.48 μM were buffered by CON cybrid mitochondria, with a step-wise decrease (followed by recovery) of Δψm evident. Δψm was lower in both ND5 mutant cybrids and ρ0 cells, and was not affected by increases in [Ca2+]. (C) Confocal images of CON cybrids, ND5 mutant cybrids and ρ0 cells showing the simultaneous staining of [Ca2+]m (fluo-4, green) and Δψm (TMRM, red). The number of the calcium aliquot and the [Ca2+] are indicated. Data is mean ± s.d. n = 3.White scale bars = 10 μm.