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Sci Rep. 2016 May 25;6:26700. doi: 10.1038/srep26700.

Alterations in voltage-sensing of the mitochondrial permeability transition pore in ANT1-deficient cells.

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Department of Medical Biochemistry, Semmelweis University MTA-SE Laboratory for Neurobiochemistry, Budapest, 1094, Hungary.
MTA-SE Lendület Neurobiochemistry Research Group, Budapest, Hungary.
Département de Neurologie, Hôpitaux Universitaires, Hôpital de Hautepierre, 67098 Strasbourg cedex, France.
Service des Maladies Héréditaires du Métabolisme, Centre de Biologie et de Pathologie Est, CHU Lyon, 69677 Bron cedex, France.
Feil Family Brain and Mind Research Institute, Weill Cornell Medical College, New York, NY 10065, USA.
Icahn School of Medicine at Mount Sinai, Department of Hematology and Medical Oncology, New York, NY 10029, USA.
Institute of Genomic Medicine and Rare Disorders, Semmelweis University, Budapest, 1083, Hungary.


The probability of mitochondrial permeability transition (mPT) pore opening is inversely related to the magnitude of the proton electrochemical gradient. The module conferring sensitivity of the pore to this gradient has not been identified. We investigated mPT's voltage-sensing properties elicited by calcimycin or H2O2 in human fibroblasts exhibiting partial or complete lack of ANT1 and in C2C12 myotubes with knocked-down ANT1 expression. mPT onset was assessed by measuring in situ mitochondrial volume using the 'thinness ratio' and the 'cobalt-calcein' technique. De-energization hastened calcimycin-induced swelling in control and partially-expressing ANT1 fibroblasts, but not in cells lacking ANT1, despite greater losses of mitochondrial membrane potential. Matrix Ca(2+) levels measured by X-rhod-1 or mitochondrially-targeted ratiometric biosensor 4mtD3cpv, or ADP-ATP exchange rates did not differ among cell types. ANT1-null fibroblasts were also resistant to H2O2-induced mitochondrial swelling. Permeabilized C2C12 myotubes with knocked-down ANT1 exhibited higher calcium uptake capacity and voltage-thresholds of mPT opening inferred from cytochrome c release, but intact cells showed no differences in calcimycin-induced onset of mPT, irrespective of energization and ANT1 expression, albeit the number of cells undergoing mPT increased less significantly upon chemically-induced hypoxia than control cells. We conclude that ANT1 confers sensitivity of the pore to the electrochemical gradient.

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