Dataset Information

Dual dynamics of mitochondrial permeability transition pore opening.

ABSTRACT: Mitochondria play an essential role in bioenergetics and cellular Ca[Formula: see text] handling. The mitochondrial permeability transition pore (mPTP) is a non-specific channel located in the inner mitochondrial membrane. Long-lasting openings of the pore allow the rapid passage of ions and large molecules, which can result in cell death. The mPTP also exhibits transient, low conductance openings that contribute to Ca[Formula: see text] homeostasis. Although many regulators of the pore have been identified, none of them uniquely governs the passage between the two operating modes, which thus probably relies on a still unidentified network of interactions. By developing a core computational model for mPTP opening under the control of mitochondrial voltage and Ca[Formula: see text], we uncovered the existence of a positive feedback loop leading to bistability. The characteristics of the two stable steady-states correspond to those of the two opening states. When inserted in a full model of Ca[Formula: see text] handling by mitochondria, our description of the pore reproduces observations in mitochondrial suspensions. Moreover, the model predicted the occurrence of hysteresis in the switching between the two modes, upon addition and removal of free Ca[Formula: see text] in the extra-mitochondrial medium. Stochastic simulations then confirmed that the pore can undergo transient openings resembling those observed in intact cells.

SUBMITTER: Wacquier B

PROVIDER: S-EPMC7054270 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Dual dynamics of mitochondrial permeability transition pore opening.

Wacquier Benjamin B Combettes Laurent L Dupont Geneviève G

Scientific reports 20200303 1

Mitochondria play an essential role in bioenergetics and cellular Ca[Formula: see text] handling. The mitochondrial permeability transition pore (mPTP) is a non-specific channel located in the inner mitochondrial membrane. Long-lasting openings of the pore allow the rapid passage of ions and large molecules, which can result in cell death. The mPTP also exhibits transient, low conductance openings that contribute to Ca[Formula: see text] homeostasis. Although many regulators of the pore have bee ...[more]

PMID: 32127570

Similar Datasets

Project description:A gentle optical examination of the mitochondrial permeability transition pore (mPTP) opening events was carried out in isolated quiescent ventricular myocytes by tracking the inner membrane potential (ΔΨM) using TMRM (tetramethylrhodamine methyl ester). Zeiss Airyscan 880 ″super-resolution" or "high-resolution" imaging was done with very low levels of illumination (0.009% laser power). In cellular areas imaged every 9 s (ROI or regions of interest), transient depolarizations of variable amplitudes occurred at increasing rates for the first 30 min. The time to first depolarization events was 8.4 min (±1.1 SEM n = 21 cells). At longer times, essentially permanent and irreversible depolarizations occurred at an increasing fraction of all events. In other cellular areas surrounding the ROI, mitochondria were rarely illuminated (once per 5 min) and virtually no permanent depolarization events occurred for over 1 h of imaging. These findings suggest that photon stress due to the imaging itself plays an important role in the generation of both the transient mPTP opening events as well as the permanent mPTP opening events. Consistent with the evidence that photon "stress" in mitochondria loaded with virtually any photon absorbing substance, generates reactive oxygen species (ROS) [1-5], we show that cyclosporine-A (CsA, 10 μM) and the antioxidant n-acetyl cysteine (NAC, 10 mM), reduced the number of events by 80% and 93% respectively. Furthermore, CsA and NAC treatment led to the virtual disappearance of permanent depolarization events. Nevertheless, all transient depolarization events in any condition (control, CsA and NAC) appeared to repolarize with a similar half-time of 30 ± 6 s (n = 478) at 37 °C. Further experiments showed quantitatively similar results in cerebral vascular smooth muscle cells, using a different confocal system, and different photon absorbing reagent (TMRE; tetramethylrhodamine ethyl ester). In these experiments, using modest power (1% laser power) transient depolarization events were seen in only 8 out of 23 cells while with higher power (8%), all cells showed transient events, which align with the level of photon stress being the driver of the effect. Together, our findings suggest that photon-induced ROS is sufficient to cause depolarization events of individual mitochondria in quiescent cells; without electrical or mechanical activity to stimulates mitochondrial metabolism, and without raising the mitochondrial matrix Ca2+. In a broad context, these findings neither support nor deny the relevance or occurrence of ΔΨM depolarization events in specific putatively physiologic mitochondrial behaviors such as MitoFlashes [6,7] or MitoWinks [8]. Instead, our findings raise a caution with regards to the physiological and pathophysiological functions attributed to singular ΔΨM depolarization events when those functions are investigated using photon absorbing substances. Nevertheless, using photon stress as a tool ("Optical Stress-Probe"), we can extract information on the activation, reversibility, permanency and kinetics of mitochondrial depolarization. These data may provide new information on mPTP, help identify the mPTP protein complex, and establish the physiological function of the mPTP protein complex and their links to MitoFlashes and MitoWinks.

Project description:Mitochondrial fission is critically involved in cardiomyocyte apoptosis, which has been considered as one of the leading causes of ischaemia/reperfusion (I/R)-induced myocardial injury. In our previous works, we demonstrate that aldehyde dehydrogenase-2 (ALDH2) deficiency aggravates cardiomyocyte apoptosis and cardiac dysfunction. The aim of this study was to elucidate whether ALDH2 deficiency promotes mitochondrial injury and cardiomyocyte death in response to I/R stress and the underlying mechanism. I/R injury was induced by aortic cross-clamping for 45 min. followed by unclamping for 24 hrs in ALDH2 knockout (ALDH2-/- ) and wild-type (WT) mice. Then myocardial infarct size, cell apoptosis and cardiac function were examined. The protein kinase C (PKC) isoform expressions and their mitochondrial translocation, the activity of dynamin-related protein 1 (Drp1), caspase9 and caspase3 were determined by Western blot. The effects of N-acetylcysteine (NAC) or PKC-? shRNA treatment on glycogen synthase kinase-3? (GSK-3?) activity and mitochondrial permeability transition pore (mPTP) opening were also detected. The results showed that ALDH2-/- mice exhibited increased myocardial infarct size and cardiomyocyte apoptosis, enhanced levels of cleaved caspase9, caspase3 and phosphorylated Drp1. Mitochondrial PKC-? translocation was lower in ALDH2-/- mice than in WT mice, and PKC-? was the opposite. Further data showed that mitochondrial PKC isoform ratio was regulated by cellular reactive oxygen species (ROS) level, which could be reversed by NAC pre-treatment under I/R injury. In addition, PKC-? inhibition caused activation of caspase9, caspase3 and Drp1Ser616 in response to I/R stress. Importantly, expression of phosphorylated GSK-3? (inactive form) was lower in ALDH2-/- mice than in WT mice, and both were increased by NAC pre-treatment. I/R-induced mitochondrial translocation of GSK-3? was inhibited by PKC-? shRNA or NAC pre-treatment. In addition, mitochondrial membrane potential (??m ) was reduced in ALDH2-/- mice after I/R, which was partly reversed by the GSK-3? inhibitor (SB216763) or PKC-? shRNA. Collectively, our data provide the evidence that abnormal PKC-?/PKC-? ratio promotes the activation of Drp1 signalling, caspase cascades and GSK-3?-dependent mPTP opening, which results in mitochondrial injury-triggered cardiomyocyte apoptosis and myocardial dysfuction in ALDH2-/- mice following I/R stress.

Dataset Information

Dual dynamics of mitochondrial permeability transition pore opening.

Publications

Dual dynamics of mitochondrial permeability transition pore opening.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets