Complex III Releases Superoxide to Both Sides of the Inner Mitochondrial Membrane*

By F. Muller, Yuhong Liu, H. Van Remmen. Journal of Biological Chemistry, 2004

1,038 citations recorded by the source corpus.

Mechanisms of mitochondrial superoxide formation remain poorly understood despite considerable medical interest in oxidative stress. Superoxide is produced from both Complexes I and III of the electron transport chain, and once in its anionic form it is too strongly charged to readily cross the inner mitochondrial membrane. Thus, superoxide production exhibits a distinct membrane sidedness or “topology.” In the present work, using measurements of hydrogen peroxide (Amplex red) as well as superoxide (modified Cypridina luciferin analog and aconitase), we demonstrate that Complex I-dependent superoxide is exclusively released into the matrix and that no detectable levels escape from intact mitochondria. This finding fits well with the proposed site of electron leak at Complex I, namely the iron-sulfur clusters of the (matrix-protruding) hydrophilic arm. Our data on Complex III show direct extramitochondrial release of superoxide, but measurements of hydrogen peroxide production revealed that this could only account for ∼50% of the total electron leak even in mitochondria lacking CuZn-superoxide dismutase. We posit that the remaining ∼50% of the electron leak must be due to superoxide released to the matrix. Measurements of (mitochondrial matrix) aconitase inhibition, performed in the presence of exogenous superoxide dismutase and catalase, confirmed this hypothesis. Our data indicate that Complex III can release superoxide to both sides of the inner mitochondrial membrane. The locus of superoxide production in Complex III, the ubiquinol oxidation site, is situated immediately next to the intermembrane space. This explains extramitochondrial release of superoxide but raises the question of how superoxide could reach the matrix. We discuss two models explaining this result.

Subfields: Molecular Biology, Neurology

View Paper: https://www.semanticscholar.org/paper/bcacb40ba445fdc31e2b07e59178b28f0aa4178d

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Citations in the corpus

Mitochondrial reactive oxygen species and cancer (2014, background): “Interestingly, while complexes I and II release ROS into the mitochondrial matrix, complex III has the ability to release ROS to both sides of the mitochondrial inner membrane [18].”
ROS-dependent signal transduction (2014, background): “Complex III-generated O2 is also released into the intermembrane space where it can traverse through voltage-dependent anion channels into the cytosol and be converted into H2O2 by SOD1 [8].”
Trends in oxidative aging theories. (2007, background): “The lack of “interaction” of various SOD knockouts is somewhat expected considering that anionic superoxide is highly membrane impermeable (reviewed in [184]), and reaffirms that the pools of superoxide are highly segregated.”
Mitochondria-Ros Crosstalk in the Control of Cell Death and Aging (2011, background): “As a consequence, they are also the primary source of cellular reactive oxygen species (ROS), especially at level of the respiratory chain complexes I and III, where electrons derived from NADH and ubiquinone can directly react with oxygen or other electron acceptors and generate free radicals [3, 4”
Mitochondrial proton and electron leaks (2010, background): “Superoxide production by complex III in the presence of antimycin A results in the release of ROS to both the matrix and intermembrane space [31,38,40].”
Exercise-Induced Oxidative Stress: Cellular Mechanisms and Impact on Muscle Force Production (2008, neutral): “of mitochondrial superoxide production (36, 272).”
The Role of Oxidative Stress in Parkinson’s Disease (2013, background): “Besides being produced by mitochondria, H2O2 can also be generated by peroxisomes [22].”
Mitochondria are required for antigen-specific T cell activation through reactive oxygen species signaling (2013, positive): “Exogenous H2O2 produced by the addition of GaO andGal rescued IL-2 induction inUqcrfs1 / cells, and treatment of WT T cells with a mitochondrial-targeted antioxidant phenocopied Uqcrfs1 / T cells, indicating that mROS, not oxidative phosphorylation, are necessary for T cell activation in vitro.”
Mitochondrial complex III is required for hypoxia-induced ROS production and cellular oxygen sensing. (2005, background): “Superoxide released to the matrix from complex I or III is unlikely to escape to the cytosol (Muller et al., 2004), although H2O2 formed in the matrix could conceivably escape.”
Mitochondrial electron transport chain, ROS generation and uncoupling (Review) (2019, background): “Muller et al (60) built two models explaining how superoxide can reach the matrix.”
Metformin inhibits mitochondrial complex I of cancer cells to reduce tumorigenesis (2014, neutral): “Mitochondrial complex III also generates superoxide into the mitochondrial intermembrane space where it escapes through VDACs to cytosol and is converted into H2O2 by SOD1 (Han et al., 2003; Muller et al., 2004).”
How mitochondria produce reactive oxygen species (2008, background): “This O 2 •− is released from complex III to both sides of the inner membrane [24,27,52,104].”