Mitochondrial Complex I Activity is Conditioned by Supercomplex I–III2–IV Assembly in Brain Cells: Relevance for Parkinson’s Disease

Abstract

The assembly of complex I (CI) with complexes III (CIII) and IV (CIV) of the mitochondrial respiratory chain (MRC) to configure I-III- or I-III-IV-containing supercomplexes (SCs) regulates mitochondrial energy efficiency and reactive oxygen species (mROS) production. However, whether the occurrence of SCs impacts on CI specific activity remains unknown to our knowledge. To investigate this issue, here we determined CI activity in primary neurons and astrocytes, cultured under identical antioxidants-free medium, from two mouse strains (C57Bl/6 and CBA) and Wistar rat, i.e. three rodent species with or without the ability to assemble CIV into SCs. We found that CI activity was 6- or 1.8-fold higher in astrocytes than in neurons, respectively, from rat or CBA mouse, which can form I-III-IV SC; however, CI activity was similar in the cells from C57Bl/6 mouse, which does not form I-III-IV SC. Interestingly, CII-III activity, which was comparable in neurons and astrocytes from mice, was about 50% lower in astrocytes when compared with neurons from rat, a difference that was abolished by antioxidants- or serum-containing media. CIV and citrate synthase activities were similar under all conditions studied. Interestingly, in rat astrocytes, CI abundance in I-III-IV SC was negligible when compared with its abundance in I-III-containing SCs. Thus, CIV-containing SCs formation may determine CI specific activity in astrocytes, which is important to understand the mechanism for CI deficiency observed in Parkinson's disease.

Mitochondrial impairment and melatonin protection in parkinsonian mice do not depend of inducible or neuronal nitric oxide synthases

“…After pre-incubation for 3 min at 25°C, the reaction was initiated by the addition of NADH (100 μM, final concentration), and the rate of decrease in the absorbance was monitored at 340 nm for 1.5 min. The incubation in the presence of 1 μM rotenone completely abolished the NADH oxidase activity measured with this method, verifying that this activity corresponds to complex I [ 50 – 52 ]. The activity of the complex I was expressed as nmol of NADH oxidized/min/mgprot.…”

Cell Biology of the Mitochondrion

“…Together, these represent the functional entity for oxidative phosphorylation, and are linked together as one very large entity called the respirasome. Measurements in nematodes and mammals have shown that the enzymatic activity of complex I (transfer of electrons through the complex) is significantly higher when it is part of the entire supercomplex than when it is isolated further (Schafer et al 2006;Suthammarak et al 2009;Lopez-Fabuel et al 2017). In nematodes, unlike mice, for example, very little complex I exists in isolation; the majority of complex I that separates on digitonin containing BNGs exists as a supercomplex: either I:III 2 : IV n or I:III 2 (Suthammarak et al 2009).…”

Mitochondrial respiratory chain disorganization in Parkinson's disease-relevant PINK1 and DJ1 mutants

“…Humans, but not C57Bl/6 mice, express active Scaf1, a CIII-CIV assembly factor (Lapuente-Brun et al 2013). Recently, we have shown that the ability of mitochondria to assemble I-III 2 -IV SCs impacts on CI activity (Lopez-Fabuel et al 2017).…”