Related Experiment Videos
Inhibition of mitochondrial permeability transition by low pH is associated with less extensive membrane protein
B M Teixeira1, A J Kowaltowski, R F Castilho
1Departamento de Patologia Clínica, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, SP, Brazil.
Abstract:
Ca2+ and inorganic phosphate-induced mitochondrial swelling and membrane protein thiol oxidation, which are associated with mitochondrial permeability transition, are inhibited by progressively decreasing the incubation medium pH between 7.2 and 6.0. Nevertheless, the detection of mitochondrial H2O2 production under these conditions is increased. Permeability transition induced by phenylarsine oxide, which promotes membrane protein thiol cross-linkage in a process independent of Ca2+ or reactive oxygen species, is also strongly inhibited in acidic incubation media. In addition, we observed that the decreased protein thiol reactivity with phenylarsine oxide or phenylarsine oxide-induced swelling at pH 6.0 is reversed by diethyl pyrocarbonate, in a hydroxylamine-sensitive manner. These results provide evidence that the inhibition of mitrochondrial permeability transition observed at lower incubation medium pH is mediated by a decrease in membrane protein thiol reactivity, related to the protonation of protein histidyl residues.
Insights
Lowering pH inhibits mitochondrial permeability transition by reducing protein thiol reactivity. This effect is linked to protonation of histidyl residues, impacting mitochondrial function.
Area of Science:
- Mitochondrial Biology
- Biochemistry
- Cellular Physiology
Background:
- Mitochondrial permeability transition (MPT) is a critical process implicated in cell death.
- MPT involves mitochondrial swelling and membrane protein thiol oxidation.
- Factors influencing MPT, such as pH and calcium, are crucial for understanding mitochondrial function.
Purpose of the Study:
- To investigate the effect of extracellular pH on calcium and inorganic phosphate-induced mitochondrial permeability transition.
- To explore the role of membrane protein thiol reactivity in pH-mediated regulation of MPT.
- To elucidate the mechanism by which acidic pH inhibits MPT.
Main Methods:
- Mitochondrial swelling and membrane protein thiol oxidation assays were performed at varying pH levels (7.2 to 6.0).
- Mitochondrial hydrogen peroxide (H2O2) production was measured under different pH conditions.
- Phenylarsine oxide (PAO) was used to induce MPT independently of Ca2+ or reactive oxygen species.
- Diethyl pyrocarbonate and hydroxylamine were employed to probe the role of protein thiols.
Main Results:
- Decreasing incubation medium pH from 7.2 to 6.0 inhibited Ca2+ and inorganic phosphate-induced MPT and associated thiol oxidation.
- Mitochondrial H2O2 production increased as pH decreased.
- PAO-induced MPT and membrane protein thiol cross-linkage were also inhibited at acidic pH.
- The inhibitory effect of acidic pH on MPT and thiol reactivity was reversed by diethyl pyrocarbonate in a hydroxylamine-sensitive manner.
Conclusions:
- The inhibition of MPT at lower incubation medium pH is mediated by a decrease in membrane protein thiol reactivity.
- Protonation of protein histidyl residues at acidic pH likely underlies the reduced thiol reactivity.
- These findings highlight the significant role of pH in regulating mitochondrial permeability transition and function.