Mitochondrial permeability transition involves dissociation of F1FO ATP synthase dimers and C-ring conformation
- PMID: 28566520
- PMCID: PMC5494524
- DOI: 10.15252/embr.201643602
Mitochondrial permeability transition involves dissociation of F1FO ATP synthase dimers and C-ring conformation
Abstract
The impact of the mitochondrial permeability transition (MPT) on cellular physiology is well characterized. In contrast, the composition and mode of action of the permeability transition pore complex (PTPC), the supramolecular entity that initiates MPT, remain to be elucidated. Specifically, the precise contribution of the mitochondrial F1FO ATP synthase (or subunits thereof) to MPT is a matter of debate. We demonstrate that F1FO ATP synthase dimers dissociate as the PTPC opens upon MPT induction. Stabilizing F1FO ATP synthase dimers by genetic approaches inhibits PTPC opening and MPT Specific mutations in the F1FO ATP synthase c subunit that alter C-ring conformation sensitize cells to MPT induction, which can be reverted by stabilizing F1FO ATP synthase dimers. Destabilizing F1FO ATP synthase dimers fails to trigger PTPC opening in the presence of mutants of the c subunit that inhibit MPT The current study does not provide direct evidence that the C-ring is the long-sought pore-forming subunit of the PTPC, but reveals that PTPC opening requires the dissociation of F1FO ATP synthase dimers and involves the C-ring.
Keywords: CYPD; ATP synthasome; ATP5G1; cyclosporine A; regulated necrosis.
© 2017 The Authors.
Figures
![Figure 1](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/5494524/bin/EMBR-18-1077-g002.gif)
- A–C
Representative traces of mouse liver mitochondria undergoing MPT in response to 100 μM CaCl2 alone or in the presence of 1 μM cyclosporine A (CsA) (A). Representative in‐gel activity assay after blue‐native PAGE (B) and quantification (C) of F1FO ATP synthase dimers (D) and monomers (M) in mouse liver mitochondria in basal conditions or after MPT induction as in panel (F). *P = 0.0001, **P = 0.0011 (ANOVA plus unpaired Student's t‐test). Results are representative of five independent experiments.
- D–F
Representative calcein/Co2+ quenching traces in HEK293T cells treated with 1 μM ionomycin (Iono), alone or in the presence of 1.6 μM CsA (D). Representative images (E) and quantification (F; n = 3) of PLA assays for F1FO ATP synthase dimers in HEK293T cells maintained in basal conditions or driven in MPT as in panel (D). *P = 0.0106, **P = 0.0137 (ANOVA plus unpaired Student's t‐test). Results are representative of three independent experiments.
![Figure EV1](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/5494524/bin/EMBR-18-1077-g003.gif)
- A
High‐resolution image of F1FO ATP synthase dimers and monomers isolated from rat heart mitochondria (HM) by the use of n‐dodecyl β‐D‐maltoside (DM) or digitonin (DIG), upon separation by blue‐native PAGE and immunostaining for ATP5A.
- B
Schematic representation of PLA assay setting in physiological conditions (left) or in the course of MPT (right).
- C
Immunoreactivity of the ATP5H‐specific antibody used in the PLA assay as compared to an antibody specific for the mitochondrial marker TOMM20.
- D
Maximum intensity projection of z‐stack from a representative HEK293T cell stained for the (immuno)fluorescence microscopy‐based detection of DNA (DAPI, blue), mitochondria (TOMM20, red), and F1FO ATP synthase dimers (PLA, green). Quantification of the PLA signal colocalizing with TOMM20 is reported (whiskers: max and min; box: 10th and 90th percentile; line: median).
- E
Assessment of transfection efficiency in HEK293T cells transfected with a control siRNA (siCTR) or a siRNA targeting ATP5H (siATP5H) for 96 h. GAPDH levels were monitored to ensure equal lane loading.
- F, G
Representative images (F) and quantification (G) of PLA assays for F1FO ATP synthase dimers in HEK293T cells transfected with siCTR or siATP5H for 96 h. The results are representative of three independent experiments. *P = 0.0001 (unpaired Student's t‐test).
- H, I
Representative images (H) and quantification (I) of PLA assays for F1FO ATP synthase dimers in ρ0 cells and their wt counterpart HPA11. The results are representative of three independent experiments. ****P = 0.0001 (unpaired Student's t‐test).
![Figure 2](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/5494524/bin/EMBR-18-1077-g004.gif)
- A
Assessment of transfection efficiency in HEK293T cells transfected with a control siRNA (siCTR) or a siRNA targeting ATPIF1 (siATPIF1) for 96 h. GAPDH levels were monitored to ensure equal lane loading.
- B, C
Representative calcein/Co2+ quenching traces (B) and quenching rate quantification (C) in HEK293T cells transfected with siCTR or siATPIF1 for 96 h, and then treated with 1 μM ionomycin (Iono). Results are representative of three independent experiments. *P = 0.0135 (unpaired Student's t‐test).
- D
Representative colocalization of ATPIF1 with TOMM20 in HEK293T cells transfected with a plasmid for ATPIF1 overexpression.
- E, F
Representative images (E) and quantification (F) of PLA assays for F1FO ATP synthase dimers in HEK293T cells co‐transfected with a plasmid coding for mtGFP and with pcDNA3 or a plasmid for the overexpression of ATPIF1. Results are representative of five independent experiments. *P = 0.0001 (unpaired Student's t‐test).
- G, H
Representative calcein/Co2+ quenching traces (G) and quenching rate quantification (H) in HEK293T cells transfected as in (E, F) and treated with 1 μM Iono. Results are representative of five independent experiments. *P = 0.0001 (unpaired Student's t‐test).
- I, J
Representative mitochondrial transmembrane potential (Δψm) recordings (I) and depolarization rate quantification (J; n = 3) in HEK293T cells transiently as in (E, F) and exposed to 500 μM H2O2. 1 μM carbonyl cyanide p‐trifluoromethoxyphenylhydrazone (FCCP) was employed as control for depolarization. Results are representative of five independent experiments. *P = 0.0001 (unpaired Student's t‐test).
![Figure EV2](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/5494524/bin/EMBR-18-1077-g005.gif)
- A–D
Representative rendering (A) and quantification of morphological parameters (count, B; average volume, C; total volume, D) in HEK293T cells transiently transfected with pcDNA3 or with a plasmid for the overexpression of ATPIF1. The results are representative of three independent experiments. Scale bar = 10 μm.
- E, F
Representative images (E) and quantification (F) of TMRM staining in HEK293T cells transiently transfected with pcDNA3 or with a plasmid for the overexpression of ATPIF1. The results are representative of five independent experiments. *P = 0.0001 (unpaired Student's t‐test). Scale bar = 10 μm.
- G, H
Representative traces (G) and quantification (H) of mitochondrial ATP‐dependent light emission in HEK293T cells transiently transfected with pcDNA3 or with a plasmid for the overexpression of ATPIF1. 75 μM N,N‐dicyclohexylcarbodiimide (DCCD) was employed to completely inhibit mitochondrial ATP synthesis. The results are representative of five independent experiments.
- I, J
Representative traces (I) and quantification (J) of mtAlphi/ECFP ratio in HEK293T cells transiently co‐transfected with pcDNA3 or with a plasmid for the overexpression of ATPIF1. 30 mM Na acetate or 30 mM NH4Cl was employed to detect the minimum and maximum ratio, respectively. The results are representative of four independent experiments.
- K, L
Representative immunoblotting for the detection of the ATP5A1 subunit after blue‐native PAGE (K) and quantification (L) of F1FO ATP synthase dimers (D) and monomers (M) in HEK293T cells transiently transfected with pcDNA3 or with a plasmid for the overexpression of ATPIF1. The results are representative of three independent experiments. *P = 0.0095 (unpaired Student's t‐test).
![Figure 3](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/5494524/bin/EMBR-18-1077-g006.gif)
- A
Assessment of transfection efficiency in HEK293T cells transfected with a control siRNA (siCTR) or a siRNA targeting ATP5I (siATP5I) for 96 h. GAPDH levels were monitored to ensure equal lane loading.
- B, C
Representative calcein/Co2+ quenching traces (B) and quenching rate quantification (C) in HEK293T cells transfected with siCTR or siATP5I for 96 h, and then treated with 1 μM ionomycin (Iono). Results are representative of five independent experiments. *P = 0.0001 (unpaired Student's t‐test).
- D
Representative colocalization of ATP5I or ATP5IG26L with TOMM20 in HEK293T cells transfected with constructs for ATP5I or ATP5IG26L overexpression, respectively.
- E, F
Representative images (E) and quantification (F) of PLA assays for F1FO ATP synthase dimers in HEK293T cells co‐transfected with a plasmid coding for mtGFP and with constructs for the overexpression of ATP5I or ATP5IG26L. Results are representative of three independent experiments. *P = 0.0001 (unpaired Student's t‐test).
- G, H
Representative calcein/Co2+ quenching traces (G) and quenching rate quantification (H) in HEK293T cells co‐transfected with an ATP5G1‐encoding construct and pcDNA or with plasmids for the overexpression of ATP5I or ATP5IG26L and treated with 1 μM Iono. Results are representative of five independent experiments. *P = 0.0007, **P = 0.0007 (ANOVA plus unpaired Student's t‐test).
- I, J
Representative mitochondrial transmembrane potential (Δψm) recordings (I) and depolarization rate quantification (J) in HEK293T cells transfected as in (G, H) and exposed to 500 μM H2O2. 1 μM carbonyl cyanide p‐trifluoromethoxyphenylhydrazone (FCCP) was added as control for depolarization. Results are representative of 3–5 independent experiments. *P = 0.0001, **P = 0.0191 (ANOVA plus unpaired Student's t‐test).
![Figure EV3](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/5494524/bin/EMBR-18-1077-g007.gif)
- A, B
Representative immunoblotting for the detection of the ATP5A1 subunit after blue‐native PAGE (A) and quantification (B) of F1FO ATP synthase dimers (D) and monomers (M) in HEK293T cells transiently transfected with pcDNA3 or with a plasmid for the overexpression of ATP5G1. The results are representative of three independent experiments and expressed as mean ± SEM.
![Figure EV4](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/5494524/bin/EMBR-18-1077-g009.gif)
- A–D
Representative rendering (A) and quantification of morphological parameters (count, B; average volume, C; total volume, D) in HEK293T cells transiently transfected with a construct for the overexpression of ATP5G1 plus pcDNA3 or a plasmid for the overexpression of ATP5I or ATP5IG26L. The results are representative of three independent experiments. Scale bar = 10 μm.
- E, F
Representative images (E) and quantification (F) of TMRM staining in HEK293T cells transiently transfected with a construct for the overexpression of ATP5G1 plus pcDNA3 or a plasmid for the overexpression of ATP5I or ATP5IG26L. The results are representative of three independent experiments. *P = 0.0060, **P = 0.0345 (Kruskal–Wallis test with Dunn's correction for multiple comparison). Scale bar = 10 μm.
- G, H
Representative traces (G) and quantification (H) of mitochondrial ATP‐dependent light emission in HEK293T cells transiently transfected with a construct for the overexpression of ATP5G1 plus pcDNA3 or a plasmid for the overexpression of ATP5I or ATP5IG26L. 75 μM DCCD was employed to completely inhibit mitochondrial ATP synthesis at the end of the assay. The results are representative of three independent experiments.
![Figure 4](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/5494524/bin/EMBR-18-1077-g008.gif)
- A
Bioinformatic prediction of the alterations imposed by the G83S and the 4GL mutations on ATP5G1 structure.
- B
Representative colocalization of ATP5G1, ATP5G1G83S or ATP5G14GL with TOMM20 in HEK293T cells transfected with constructs for ATP5G1, ATP5G1G83S or ATP5G14GL overexpression, respectively. Scale bar = 10 μm.
- C, D
Representative images (C) and quantification (D) of PLA assays for F1FO ATP synthase dimers in HEK293T cells co‐transfected with a plasmid coding for mtGFP and constructs for the overexpression of ATP5G1, ATP5G1G83S or ATP5G14GL. Results are representative of three independent experiments. Scale bar = 10 μm.
- E, F
Representative calcein/Co2+ quenching recordings (E) and quenching rate quantification (F) in HEK293T cells transfected as in (C, D) and then treated with 1 μM ionomycin (Iono). Results are representative of three independent experiments. *P = 0.0352, **P = 0.0453 (ANOVA plus unpaired Student's t‐test).
- G, H
Representative mitochondrial transmembrane potential (Δψm) readings (G) and depolarization rate quantification (H) in HEK293T cells transfected as in (C, D) and then exposed to 500 μM H2O2. 1 μM carbonyl cyanide p‐trifluoromethoxyphenylhydrazone (FCCP) was employed at the end of the assay as a positive control for depolarization. Results are representative of five independent experiments. *P = 0.0006, **P = 0.0270 (ANOVA plus unpaired Student's t‐test).
- I, J
Representative calcein/Co2+ quenching traces (I) and quenching rate quantification (J) in HEK293T cells pre‐treated with 1.6 μM cyclosporine A (CsA), 10 μM oligomycin, 15 μM N,N‐dicyclohexylcarbodiimide (DCCD) or 10 μM venturicidin, and then exposed to 1 μM Iono. The results are representative of three independent experiments. *P = 0.0001, **P = 0.0033 (ANOVA plus unpaired Student's t‐test).
![Figure 5](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/5494524/bin/EMBR-18-1077-g010.gif)
- A, B
Representative calcein/Co2+ quenching recordings (A) and quenching rate quantification (B) in HEK293T cells transfected with an empty plasmid or with a construct for the overexpression of ATPIF1, combined with an ATP5G1‐ or an ATP5G14GL‐encoding plasmid, and exposed to 1 μM ionomycin (Iono). Results are representative of three independent experiments. *P = 0.0030, **P = 0.0035, ***P = 0.0078 (ANOVA plus unpaired Student's t‐test).
- C, D
Representative calcein/Co2+ quenching recordings (C) and quenching rate quantification (D) in HEK293T cells transfected with a control siRNA (siCTR) or with a siRNA specific for ATP5I (siATP5I), combined with an ATP5G1‐ or an ATP5G1G83S‐encoding plasmid, and then treated with 1 μM Iono. Results are representative of three independent experiments. *P = 0.0001, **P = 0.00001, ***P = 0.0235 (ANOVA plus unpaired Student's t‐test).
- E
Design of the experimental approach to study cardiac ischemia/reperfusion damage ex vixo. P, pressure readings. T, TUNEL assay.
- F
Quantification of LVEDP in rat hearts subjected to ischemia ex vivo and then reperfused with vehicle only (black), or with vehicle supplemented with 0.2 μM cyclosporine A (CsA; green) or 0.2 μM N,N‐dicyclohexylcarbodiimide (DCCD; blue), as detailed in panel (E). Results are representative of four independent experiments and expressed as individual readings. *P = 0.0001, **P = 0.0032 (ANOVA plus unpaired Student's t‐test).
- G, H
Representative images (G) and quantification (H) of TUNEL assays in rat hearts subjected to ischemia ex vivo and then reperfused with vehicle only, or with vehicle supplemented with 0.2 μM CsA or 0.2 μM DCCD, as detailed in panel (E). TO‐PRO®‐3 was employed as a nuclear counterstain. Results are representative of three independent experiments. *P = 0.0054, **P = 0.0006 (ANOVA plus unpaired Student's t‐test).
Comment in
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ATP synthase complex and the mitochondrial permeability transition pore: poles of attraction.EMBO Rep. 2017 Jul;18(7):1041-1042. doi: 10.15252/embr.201744412. Epub 2017 Jun 19. EMBO Rep. 2017. PMID: 28630136 Free PMC article.
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