Abstract
BackgroundThe mitochondrial voltage-dependent anion channel (VDAC) is increasingly implicated in the control of apoptosis. We have studied the effects the mitochondrial DNA (mtDNA) tRNAIle mutation on VDAC expression, localization, and apoptosis.MethodsLymphoblastoid cell lines were derived from 3 symptomatic and 1 asymptomatic members of a family with hypertension associated with the A4263G tRNAIle mutation as well as from control subjects. Mitochondrial potential (ΔΨm) and apoptosis were measured by flow cytometry; co-localization of VDAC and Bax was evaluated by confocal microscopy.ResultsExpression of VDAC and Bax in mtDNA cell lines was found to be increased compared to controls, while expression of the small conductance calcium-dependant potassium channel (sKCa) was unchanged. Confocal imaging revealed co-localization of VDAC/Bax on the outer mitochondrial membrane of A4263G cell lines but not from controls. Flow cytometry indicated that the mitochondrial potential was decreased by 32% in mutated cells versus controls while rates of apoptosis were increased (P < 0.05). The difference was attenuated by Cyclosporin A (CsA, 2 μM), a blocker of VDAC.ConclusionWe conclude that increased expression of mitochondrial VDAC and subcellular co-localization of VDAC/Bax increases mitochondrial permeability and apoptosis in cell lines carrying the mtDNA tRNAIle A4263G mutation.
Highlights
The mitochondrial voltage-dependent anion channel (VDAC) is increasingly implicated in the control of apoptosis
Expression of VDAC, Bax and sKCa To study the effects of the mitochondrial tRNAIle A4263G mutation on mitochondrial function, lymphoblastoid cell lines were isolated from familial carriers of the mutation (Figure 1) and from controls
We investigated the effects of Cyclosporin A (CsA), a selective inhibitor of VDAC, on VDAC and Bax mRNA levels
Summary
The mitochondrial voltage-dependent anion channel (VDAC) is increasingly implicated in the control of apoptosis. We have studied the effects the mitochondrial DNA (mtDNA) tRNAIle mutation on VDAC expression, localization, and apoptosis. Hypertension is an established risk factor for coronary heart disease, stroke, congestive heart failure and renal dysfunction, and is the major modifiable risk factor of poor prognosis in a variety of cardiovascular diseases. We previously reported on families with an inherited disposition to essential hypertension; some (page number not for citation purposes). BMC Medical Genetics 2009, 10:114 http://www.biomedcentral.com/1471-2350/10/114 families showed an obvious pattern of maternal inheritance indicative of a mitochondrial disorder [2,3,4,5]. In a previous study on a large Chinese Han family with maternally-inherited hypertension we uncovered a mutation in the mitochondrial A4263G tRNAIle gene. The change was inferred to influence amino acid charging of tRNA [6] and was likely to lead to translational amino-acid substitutions in some mitochondrial proteins, with major consequences for mitochondrial function
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