title: Life cell quantification of mitochondrial membrane potential at the single organelle level.
abstract: Mitochondrial membrane potential (Deltapsi) is key to mitochondrial function and cellular survival. Here, we aimed to develop an automated protocol allowing sensitive quantification of Deltapsi in living cells at the level of individual mitochondria. Human skin fibroblasts were stained with the fluorescent cation tetramethyl rhodamine methyl ester (TMRM), which is sequestered by mitochondria according to their Deltapsi. Cells were visualized by videomicroscopy and the acquired images were processed to generate a mitochondria-specific mask. The latter was superimposed on the original image to allow quantification of TMRM fluorescence. Following validation, our approach revealed that mitochondria with different Deltapsi coexisted within the same cell. Furthermore, our method allowed reproducible detection of small (<10%) reductions in TMRM intensity induced by the complex III inhibitor antimycin A. Mitochondrial uncoupling by p-trifluoromethoxy carbonyl cyanide phenyl hydrazone (FCCP) greatly reduced mitochondrial TMRM fluorescence. Under these conditions faithful mask calculation and TMRM intensity analysis were still possible using a mitochondria-targeted green fluorescence protein (mitoAcGFP1), expressed in the cells using baculoviral transfection.
authors.affiliation: Department of Membrane Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Felix
authors.initials: F
authors.lastname: Distelmaier
authors.forename: Werner J H
authors.initials: WJ
authors.lastname: Koopman
authors.forename: Epifania R
authors.initials: ER
authors.lastname: Testa
authors.forename: Arjan S
authors.initials: AS
authors.lastname: de Jong
authors.forename: Herman G
authors.initials: HG
authors.lastname: Swarts
authors.forename: Ertan
authors.initials: E
authors.lastname: Mayatepek
authors.forename: Jan A M
authors.initials: JA
authors.lastname: Smeitink
authors.forename: Peter H G M
authors.initials: PH
authors.lastname: Willems
mesh_terms: D002478:Cells, Cultured; D005347:Fibroblasts / Q000648:ultrastructure; D005456:Fluorescent Dyes / Q000737:chemistry; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000502:physiology*; D008928:Mitochondria / Q000502:physiology* / Q000648:ultrastructure; D012235:Rhodamines / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; D012235:Rhodamines; C401833:tetramethylrhodamine methyl ester; D049452:Green Fluorescent Proteins