scholarly journals Long Lasting Reversibility of the Mitochondrial Permeability Transition in Saccharomyces cerevisiae

2021 ◽  
Author(s):  
Lilia Morales-García ◽  
Carolina Ricardez -García ◽  
Paulina Castañeda-Tamez ◽  
Natalia Chiquete-Félix ◽  
Salvador Uribe-Carvajal
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Transmembrane Potential ◽  
Mitochondrial Permeability Transition ◽  
Energy Charge ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Isolated Mitochondria ◽  
Opening And Closing ◽  
Open Position

Abstract: The Saccharomyces cerevisiae mitochondrial unspecific pore (ScMUC) is an uncoupling unspecific pore that shares some similarities with the mammalian permeability transition pore (mPTP). When open, both channels deplete ion and proton gradients across the inner mitochon-drial membrane. However, the role of mPTP is to reversibly open to protect cells against stress. If mPTP remains stuck in the open position the cell dies. In contrast, ScMUC is probably dedicated to deplete oxygen from the medium in order to kill competing organisms. Such O2 depletion would be better achieved if oxidative phosphorylation is at least mildly uncoupled. Still, when oxida-tive phosphorylation is needed ScMUC should be able to close. To test this, the reversible opening and closing of ScMUC in the presence of different effectors was tested in isolated mitochondria from S. cerevisiae. Evaluations were conducted at different incubation times, monitoring the rate of O2 consumption, mitochondrial swelling and the transmembrane potential. It was observed that ScMUC did remain reversibly open for minutes. A low energy charge (ATP/ADP) closed the chan-nel. In addition, high Ca2+ promoted closing and it was a highly powerful effector.

scholarly journals Bax-induced Cytochrome C Release from Mitochondria Is Independent of the Permeability Transition Pore but Highly Dependent on Mg2+ Ions

1998 ◽  
Vol 143 (1) ◽  
pp. 217-224 ◽  
Author(s):  
Robert Eskes ◽  
Bruno Antonsson ◽  
Astrid Osen-Sand ◽  
Sylvie Montessuit ◽  
Christoph Richter ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Cyclosporin A ◽  
Mitochondrial Permeability Transition Pore ◽  
Mitochondrial Permeability Transition ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Cytochrome C Release ◽  
Mitochondrial Permeability ◽  
Isolated Mitochondria ◽  
Mammalian Homologue

Bcl-2 family members either promote or repress programmed cell death. Bax, a death-promoting member, is a pore-forming, mitochondria-associated protein whose mechanism of action is still unknown. During apoptosis, cytochrome C is released from the mitochondria into the cytosol where it binds to APAF-1, a mammalian homologue of Ced-4, and participates in the activation of caspases. The release of cytochrome C has been postulated to be a consequence of the opening of the mitochondrial permeability transition pore (PTP). We now report that Bax is sufficient to trigger the release of cytochrome C from isolated mitochondria. This pathway is distinct from the previously described calcium-inducible, cyclosporin A–sensitive PTP. Rather, the cytochrome C release induced by Bax is facilitated by Mg2+ and cannot be blocked by PTP inhibitors. These results strongly suggest the existence of two distinct mechanisms leading to cytochrome C release: one stimulated by calcium and inhibited by cyclosporin A, the other Bax dependent, Mg2+ sensitive but cyclosporin insensitive.

Protectors of the mitochondrial permeability transition pore activated by iron and doxorubicin

2021 ◽  
Vol 21 ◽  
Author(s):  
Tatiana A. Fedotcheva ◽  
Nadezhda I. Fedotcheva
Keyword(s):  
Mitochondrial Permeability Transition Pore ◽  
Mitochondrial Permeability Transition ◽  
Membrane Damage ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Selective Electrode ◽  
Mitochondrial Permeability ◽  
Isolated Mitochondria ◽  
Mptp Opening ◽  
Dependent Cell

Aim: The study of action of iron, DOX, and their complex on the mitochondrial permeability transition pore (MPTP) opening and the detection of possible protectors of MPTP in the conditions close to mitochondria-dependent ferroptosis. Background: The toxicity of doxorubicin (DOX) is mainly associated with the free iron accumulation and mitochondrial dysfunction. DOX can provoke ferroptosis, iron-dependent cell death driven by the membrane damage. The mitochondrial permeability transition pore (MPTP) is considered as a common pathway leading to the development of apoptosis, necrosis, and, possibly, ferroptosis. The influence of DOX on the Ca2+ -induced opening of MPTP in the presence of iron has not yet been studied. Objective: The study was conducted on isolated liver and heart mitochondria. MPTP and succinate-ubiquinone oxidoreductase were studied as targets of DOX in mitochondria-dependent ferroptosis. Methods: The study was conducted on isolated mitochondria of the liver and heart. Changes of threshold calcium concentrations required for MPTP opening were measured by a Ca2+ selective electrode, mitochondrial membrane potential was registered by tetraphenylphosphonium (TPP+)-selective electrode, and mitochondrial swelling was recorded as a decrease in absorbance at 540 nm. The activity of succinate dehydrogenase (SDH) was determined by the reduction of the electron acceptor DCPIP. Conclusion: MPTP and the respiratory complex II are identified as the main targets of the iron-dependent action of DOX on the isolated mitochondria. All MPTP protectors tested abolished or weakened the effect of iron and a complex of iron with DOX on Ca2+ -induced MPTP opening, acting in different stages of MPTP activation. These data open new approaches to the modulation of the toxic influence of DOX on mitochondria with the aim to reduce their dysfunction

Abstract 3782: β2-Adrenergic Receptor Signaling Positively Modulates Pro-Survival Kinases and Ameliorates Mitochondrial Dysfunction during Doxorubicin Cardiotoxicity

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Giovanni Fajardo ◽  
Mingming Zhao ◽  
Gerald Berry ◽  
Daria Mochly-Rosen ◽  
Daniel Bernstein
Keyword(s):  
Mitochondrial Dysfunction ◽  
Mitochondrial Permeability Transition Pore ◽  
Mitochondrial Permeability Transition ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Surface Receptors ◽  
Β2 Adrenergic Receptor ◽  
Improvement In Survival ◽  
Complex I Activity

β2-adrenergic receptors (β2-ARs) modulate cardioprotection through crosstalk with multiple pathways. We have previously shown that β2-ARs are cardioprotective during acute exposure to Doxorubicin (DOX). DOX cardiotoxicity is mediated through a Ca 2+ -dependent opening of the mitochondrial permeability transition pore (MPT) and mitochondrial dysfunction, however the upstream signals linking cell surface receptors and the MPT are not clear. The purpose of this study was to assess crosstalk between β2-AR signaling and mitochondrial function in DOX toxicity. DOX 10 mg/kg was administered to β2−/− and WT mice. Whereas there was no mortality in WT, 85% of β2−/− mice died within 30 min (n=20). Pro- and anti-survival kinases were assessed by immunobloting. At baseline, β2−/− showed normal levels of ϵPKC, but a 16% increase in δPKC compared to WT (p<0.05). After DOX, β2−/− showed a 64% decrease in ϵPKC (p<0.01) and 22% increase in δPKC (p<0.01). The ϵPKC activator ΨϵRACK decreased mortality by 40% in β2−/− mice receiving DOX; there was no improvement in survival with the δPKC inhibitor δV1–1. After DOX, AKT activity was decreased by 76% (p<0.01) in β2−/− but not in WT. The α1-AR blocker prazosin, inhibiting signaling through Gαq, restored AKT activity and reduced DOX mortality by 47%. We next assessed the role of mitochondrial dysfunction in β2−/− mediated DOX toxicity. DOX treated β2−/− mice, but not WT, show marked vacuolization of mitochondrial cristae. Complex I activity decreased 31% in β2−/− mice with DOX; but not in WT. Baseline rate of Ca2+ release and peak [Ca2+]i ratio were increased 85% and 17% respectively in β2−/− myocytes compared to WT. Verapamil decreased mortality by 27% in DOX treated β2−/− mice. Cyclosporine, a blocker of both MPT and calcineurin, reduced DOX mortality to 50%. In contrast, FK506, a blocker of calcineurin but not the MPT, did not reduce DOX mortality. Cyclosporine prevented the decrease in AKT activity in β2−/− whereas FK506 did not. These findings suggest that β2-ARs modulate pro-survival kinases and attenuate mitochondrial dysfunction during DOX cardiotoxicity; absence of β2-ARs enhances DOX toxicity via negative regulation of survival kinases and enhancement of intracellular Ca2+, sensitizing mitochondria to opening of the MPT.

Mitochondrial control of apoptosis: an overview

1999 ◽  
Vol 66 ◽  
pp. 1-15 ◽  
Author(s):  
Guido Kroemer
Keyword(s):  
Transmembrane Potential ◽  
Mitochondrial Permeability Transition ◽  
Ion Selectivity ◽  
Permeability Transition ◽  
Critical Event ◽  
Intact Cells ◽  
Isolated Mitochondria ◽  
Pore Opening ◽  
Mitochondrial Megachannel

The mitochondrial permeability transition (PT) pore, also called the mitochondrial megachannel, is a multiprotein complex formed at the contact site between the mitochondrial inner and outer membranes, exactly the same location at which Bax, Bcl-2 and Bcl-XL are particularly abundant. The PT pore participates in the regulation of matrix Ca2+, pH, transmembrane potential and volume, and functions as a Ca2+-, voltage-, pH- and redox-gated channel with several levels of conductance and little, if any, ion selectivity. We have obtained three independent lines of evidence implicating the mitochondrial PT pore in apoptosis. First, in intact cells, apoptosis is accompanied by an early dissipation of the mitochondrial transmembrane potential, ΔΨm. In several models of apoptosis, specific agents inhibiting the mitochondrial PT pore abolish this dissipation of the ΔΨm and simultaneously prevent activation of downstream caspases and endonucleases, indicating that PT pore opening can be a critical event of the apoptotic process. Secondly, mitochondria are rate-limiting for caspase and nuclease activation in several cell-free systems of apoptosis. Isolated mitochondria release apoptogenic factors capable of activating pro-caspases or endonucleases upon opening of the mitochondrial megachannel in vitro. Thirdly, opening of the purified PT pore complex reconstituted into liposomes is inhibited by recombinant Bcl-2 or Bcl-XL, two apoptosis-inhibitory proteins that also prevent PT pore opening in cells and isolated mitochondria. Altogether, our results suggest that PT pore opening is sufficient and (mostly) necessary for triggering apoptosis. The implications of these findings are examined in the light of pharmacological interventions in apoptosis.

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