Lack of Cytochrome c in Mouse Fibroblasts Disrupts Assembly/Stability of Respiratory Complexes I and IV

Department of Neurology and Department of Cell Biology and Anatomy, University of Miami Miller School of Medicine, Miami, Florida 33136, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 02/2009; 284(7):4383-91. DOI: 10.1074/jbc.M805972200
Source: PubMed


Cytochrome c (cyt c) is a heme-containing protein that participates in electron transport in the respiratory chain and as a signaling molecule
in the apoptotic cascade. Here we addressed the effect of removing mammalian cyt c on the integrity of the respiratory complexes in mammalian cells. Mitochondria from cyt c knockout mouse cells lacked fully assembled complexes I and IV and had reduced levels of complex III. A redox-deficient mutant
of cyt c was unable to rescue the levels of complexes I and IV. We found that cyt c is associated with both complex IV and respiratory supercomplexes, providing a potential mechanism for the requirement for
cyt c in the assembly/stability of complex IV.

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    • "This result seems inconsistency, but mitochondrial membrane permeabilization is a complex process and includes several mechanisms such as Bcl-2 family proteins regulation and lipid peroxidation, therefore the simplest explanation is that other reasons that affect Δψ might to be remained which needed further research. In recent years, works from several laboratories showed that the mitochondrial membrane potential was essential for the membrane anchorage of the respiratory supercomplexes [40], which might serve to reduce the diffusion distance of the substrates, to improve electron transfer, to decrease the reactive oxygen species formation and to stabilize the individual complexes [41]. In our study, we found that the stability of mitochondrial membrane potential promoted PMA-induced cell differentiation, possibly because of the increased stability of supercomplexes. "
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    ABSTRACT: Mitochondria are involved in the regulation of cell differentiation processes, but its function changes and molecular mechanisms are not yet clear. In this study, we found that mitochondrial functions changed obviously when K562 cells were induced to megakaryocytic differentiation by phorbol 12-myristate 13-acetate (PMA). During the cell differentiation, the reactive oxygen species (ROS) level was increased, mitochondrial membrane potential declined and respiratory chain complex IV activity was decreased. Treatment with specific inhibitor of mitochondrial respiratory chain complex IV led to a significant inhibition in mitochondrial membrane potential and reduction of PMA-induced cell differentiation. However, treatment with cyclosporine A, a stabilization reagent of mitochondrial membrane potential, did not improve the down-regulation of mitochondrial respiratory chain complex IV induced by PMA. Furthermore, we found that the level of the complex IV core subunit COX3 and mitochondrial transport-related proteins Tim9 and Tim10 were decreased during the differentiation of K562 cells induced by PMA, suggesting an important role of these factors in mitochondrial functional changes. Our results suggest that changes in mitochondrial functions are involved in the PMA-induced K562 cell differentiation process, and the maintenance of the steady-state of mitochondrial functions plays a critical role in the regulation of cell differentiation.
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    • "revealed that: (iii) isolated respirasomes mediate electron transfer from NADH to O 2 and (iv) respirasomes can contain CoQ 10 and cyt-c. The latter suggests that also cyt-c is associated with respiratory supercomplexes, compatible with the observation that fibroblasts from cyt-c knockout mice lacked fully assembled CI and CIV and displayed lower levels of CIII (Vempati et al, 2009), and evidence that cyt-c and CoQ 10 are functionally compartmentalized (Benard et al, 2008). The first protein factor (HIGD2A) required for respirasome assembly and stability in mammals was recently identified (Chen et al, 2012; Strogolova et al, 2012; Vukotic et al, 2012). "
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    ABSTRACT: Mitochondrial oxidative phosphorylation (OXPHOS) sustains organelle function and plays a central role in cellular energy metabolism. The OXPHOS system consists of 5 multisubunit complexes (CI-CV) that are built up of 92 different structural proteins encoded by the nuclear (nDNA) and mitochondrial DNA (mtDNA). Biogenesis of a functional OXPHOS system further requires the assistance of nDNA-encoded OXPHOS assembly factors, of which 35 are currently identified. In humans, mutations in both structural and assembly genes and in genes involved in mtDNA maintenance, replication, transcription, and translation induce 'primary' OXPHOS disorders that are associated with neurodegenerative diseases including Leigh syndrome (LS), which is probably the most classical OXPHOS disease during early childhood. Here, we present the current insights regarding function, biogenesis, regulation, and supramolecular architecture of the OXPHOS system, as well as its genetic origin. Next, we provide an inventory of OXPHOS structural and assembly genes which, when mutated, induce human neurodegenerative disorders. Finally, we discuss the consequences of mutations in OXPHOS structural and assembly genes at the single cell level and how this information has advanced our understanding of the role of OXPHOS dysfunction in neurodegeneration.
    Preview · Article · Nov 2012 · The EMBO Journal
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    • "In addition to its role as electron carrier in the mitochondrial respiratory chain, CYTc has been linked to other important cellular processes , triggering programmed cell death in mammals [16] and participating in the redox-mediated import of proteins to the intermembrane space in yeast [17]. Mutant analyses in yeast and mammals revealed that CYTc is structurally required for the assembly and stability of Complexes I, III and IV [18] [19] [20]. A binding site for CYTc within the structure of respiratory supercomplexes was proposed in yeast [21] suggesting that this supramolecular configuration could be the basis for efficient electron transfer from Complex III to Complex IV [22]. "
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    ABSTRACT: We studied the role of cytochrome c (CYTc), which mediates electron transfer between Complexes III and IV, in cellular events related with mitochondrial respiration, plant development and redox homeostasis. We analyzed single and double homozygous mutants in both CYTc-encoding genes from Arabidopsis: CYTC-1 and CYTC-2. While individual mutants were similar to wild-type, knock-out of both genes produced an arrest of embryo development, showing that CYTc function is essential at early stages of plant development. Mutants in which CYTc levels were extremely reduced respective to wild-type had smaller rosettes with a pronounced decrease in parenchymatic cell size and an overall delay in development. Mitochondria from these mutants had lower respiration rates and a relative increase in alternative respiration. Furthermore, the decrease in CYTc severely affected the activity and the amount of Complex IV, without affecting Complexes I and III. Reactive oxygen species levels were reduced in these mutants, which showed induction of genes encoding antioxidant enzymes. Ascorbic acid levels were not affected, suggesting that a small amount of CYTc is enough to support its normal synthesis. We postulate that, in addition to its role as an electron carrier between Complexes III and IV, CYTc influences Complex IV levels in plants, probably reflecting a role of this protein in Complex IV stability. This double function of CYTc most likely explains why it is essential for plant survival.
    Full-text · Article · Apr 2012 · Biochimica et Biophysica Acta
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