Regulation Of Mitochondrial Dynamics Research Articles

Comprehensive analysis of epigenetics regulation, prognostic and the correlation with immune infiltrates of GPX7 in adult gliomas

Gliomas are the most commonly occurring malignant brain tumor characterized by an immunosuppressive microenvironment accompanied by profound epigenetic changes, thus influencing the prognosis. Glutathione peroxidase 7 (GPX7) is essential for regulating reactive oxygen species homeostasis under oxidative stress. However, little is known about the function of GPX7 in gliomas. In this study, we hypothesized that GPX7 methylation status could influence biological functions and local immune responses that ultimately impact prognosis in adult gliomas. We conducted an integrated bioinformatics analysis mining GPX7 DNA methylation status, transcriptional and survival data of glioma patients. We discovered that GPX7 was remarkably increased in glioma tissues and cell lines, and was associated with poor prognosis. This upregulation was significantly linked to clinicopathological and molecular features, besides being expressed in a cell cycle-dependent manner. Our results consistently demonstrated that upregulation of GPX7 is tightly modulated by epigenetic processes, which also impacted the overall survival of patients with low-grade gliomas (LGG). Based on the analysis of biological functions, we found that GPX7 might be involved in immune mechanisms involving both innate and adaptive immunity, type I interferon production and regulation of synaptic transmission in LGG, whereas in GBM, it is mainly related to metabolic regulation of mitochondrial dynamics. We also found that GPX7 strongly correlates with immune cell infiltration and diverse immune cell markers, suggesting its role in tumor-specific immune response and in regulating the migration of immune cell types to the tumor microenvironment. Combining these multiple data, we provided the first evidence regarding the epigenetic-mediated regulatory mechanisms underlying GPX7 activation in gliomas. Furthermore, our study brings key insights into the significant effect of GPX7 in modulating both immune molecules and in immune cell infiltration in the microenvironment of gliomas, which might impact the patient outcome, opening up future opportunities to regulate the local immune response.

Selenium Attenuates TBHP-Induced Apoptosis of Nucleus Pulposus Cells by Suppressing Mitochondrial Fission through Activating Nuclear Factor Erythroid 2-Related Factor 2.

Intervertebral disc (IVD) degeneration (IDD), the leading cause of low back pain (LBP), remains intractable due to a lack of effective therapeutic strategies. Several lines of studies have documented that nucleus pulposus cell (NPC) death induced by excessive oxidative stress is a crucial contributor to IDD. However, the concrete role and regulation mechanisms have not been fully clarified. Selenium (Se), a vital prosthetic group of antioxidant enzymes, is indispensable for maintaining redox homeostasis and promoting cell survival. However, no light was shed on the role of Se on IDD progression, especially regulation on mitochondrial dynamics and homeostasis. To fill this research gap, the current study focuses on the effects of Se, including sodium selenite (SS) and selenomethionine (Se-Met), on IDD progression and the underlying mechanisms. In vitro, we found that both SS and Se-Met alleviated tert-butyl hydroperoxide- (TBHP-) induced oxidative stress, protected mitochondrial function, and inhibited apoptosis of NPCs. Further experiments indicated that Se suppressed TBHP-induced mitochondrial fission and rescued the imbalance of mitochondrial dynamics. Promoting mitochondrial fission by carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP) partially counteracted the cytoprotective effects of Se. Moreover, blocking nuclear factor erythroid 2-related factor 2 (Nrf2) with ML385 proved that the effect of Se on regulating mitochondrial dynamics was attributed to the activation of the Nrf2 pathway. In the puncture-induced rat IDD model, a supplement of Se-Met ameliorated degenerative manifestations. Taken together, our results demonstrated that Se suppressed TBHP-induced oxidative stress and mitochondrial fission by activating the Nrf2 pathway, thereby inhibiting the apoptosis of NPCs and ameliorating IDD. Regulation of mitochondrial dynamics by Se may have a potential application value in attenuating the pathological process of IDD.

Caveolin-1 controls mitochondrial damage and ROS production by regulating fission - fusion dynamics and mitophagy

As essential regulators of mitochondrial quality control, mitochondrial dynamics and mitophagy play key roles in maintenance of metabolic health and cellular homeostasis. Here we show that knockdown of the membrane-inserted scaffolding and structural protein caveolin-1 (Cav-1) and expression of tyrosine 14 phospho-defective Cav-1 mutant (Y14F), as opposed to phospho-mimicking Y14D, altered mitochondrial morphology, and increased mitochondrial matrix mixing, mitochondrial fusion and fission dynamics as well as mitophagy in MDA-MB-231 triple negative breast cancer cells. Further, we found that interaction of Cav-1 with mitochondrial fusion/fission machinery Mitofusin 2 (Mfn2) and Dynamin related protein 1 (Drp1) was enhanced by Y14D mutant indicating Cav-1 Y14 phosphorylation prevented Mfn2 and Drp1 translocation to mitochondria. Moreover, limiting mitochondrial recruitment of Mfn2 diminished formation of the PINK1/Mfn2/Parkin complex required for initiation of mitophagy resulting in accumulation of damaged mitochondria and ROS (mtROS). Thus, these studies indicate that phospho-Cav-1 may be an important switch mechanism in cancer cell survival which could lead to novel strategies for complementing cancer therapies.

Mitochondrial Quality Control: the Role in Cardiac Injury.

The heart is a highly energy-dependent organ, and most of its energy is provided by mitochondrial oxidative phosphorylation. Therefore, maintaining a well-functioning mitochondrial population is of paramount importance for cardiac homeostasis, since damaged mitochondria produce less adenosine triphosphate (ATP) and generate higher amounts of reactive oxygen species (ROS). Mitochondrial dysfunction is associated with the development of many diseases, including cardiovascular disorders. In this article, we review the role of mitochondria as key determinants of acute myocardial ischemic/reperfusion injury (IRI) and also diabetic cardiomyopathy. The structure and function of mitochondria are regulated by the mitochondrial quality control (MQC) system. Mitochondrial quality control mechanisms involve a series of adaptive responses that preserve mitochondrial structure and function as well as ensure cardiomyocyte survival and cardiac function after injury. This review summarizes the basic mechanisms of MQC, including mitochondrial dynamics (fusion and fission), mitophagy and mitochondrial biogenesis. Mitochondrial dynamics are mainly controlled by the level of fission and fusion proteins and also by their post-translational modifications. In addition, this review aims to provide a contemporary view of the importance of miRNA molecules in the regulation of mitochondrial dynamics at the post-transcriptional level. Thus, miRNAs play an important role not only in the pathogenesis and prognosis of cardiac diseases, but can also be an important therapeutic target.

βIII-Tubulin Structural Domains Regulate Mitochondrial Network Architecture in an Isotype-Specific Manner.

βIII-tubulin is a neuronal microtubule protein that is aberrantly expressed in epithelial cancers. The microtubule network is implicated in regulating the architecture and dynamics of the mitochondrial network, although the isotype-specific role for β-tubulin proteins that constitute this microtubule network remains unclear. High-resolution electron microscopy revealed that manipulation of βIII-tubulin expression levels impacts the volume and shape of mitochondria. Analysis of the structural domains of the protein identifies that the C-terminal tail of βIII-tubulin, which distinguishes this protein from other β-tubulin isotypes, significantly contributes to the isotype-specific effects of βIII-tubulin on mitochondrial architecture. Mass spectrometry analysis of protein–protein interactions with β-tubulin isotypes identifies that βIII-tubulin specifically interacts with regulators of mitochondrial dynamics that may mediate these functional effects. Advanced quantitative dynamic lattice light sheet imaging of the mitochondrial network reveals that βIII-tubulin promotes a more dynamic and extended reticular mitochondrial network, and regulates mitochondrial volume. A regulatory role for the βIII-tubulin C-terminal tail in mitochondrial network dynamics and architecture has widespread implications for the maintenance of mitochondrial homeostasis in health and disease.

Regulation of Mitochondrial Dynamics by Aerobic Exercise in Cardiovascular Diseases.

Mitochondrial dynamics, including continuous biogenesis, fusion, fission, and autophagy, are crucial to maintain mitochondrial integrity, distribution, size, and function, and play an important role in cardiovascular homeostasis. Cardiovascular health improves with aerobic exercise, a well-recognized non-pharmaceutical intervention for both healthy and ill individuals that reduces overall cardiovascular disease (CVD) mortality. Increasing evidence shows that aerobic exercise can effectively regulate the coordinated circulation of mitochondrial dynamics, thus inhibiting CVD development. This review aims to illustrate the benefits of aerobic exercise in prevention and treatment of cardiovascular disease by modulating mitochondrial function.

Molecular Regulations of FUNDC1 at ER-Mitochondria Contacts Under Hypoxic Stress.

A recent research paper published in Journal of Cell Biology by Chen and colleagues describes a novel mechanism by which the MAM (Mitochondrial-associated endoplasmic reticulum membrane) protein FUNDC1 (FUN14 domain-containing protein 1) regulates mitochondrial division through altered protein post-translational modifications under hypoxic stress. The authors found that in a hypoxic environment, the endoplasmic reticulum-localized deubiquitinating enzyme USP19 accumulates at the MAM and interacts with the enriched mitochondrial outer membrane protein FUNDC1, which subsequently induces its deubiquitination and promotes the oligomerization and activity of DRP1, and mitochondria eventually divide in the presence of DRP1. This article provides new insights into the regulation of mitochondrial dynamics by FUNDC1 under hypoxic condition.

Opa1-mediated mitochondrial dynamics is important for osteoclast differentiation.

Opatic atrophy 1 (Opa1) is a mitochondrial GTPase that regulates mitochondrial fusion and maintenance of cristae architecture. Osteoclasts are mitochondrial rich-cells. However, the role of Opa1 in osteoclasts remains unclear. Here, we demonstrate that Opa1- deficient osteoclast precursor cells do not undergo efficient osteoclast differentiation and exhibit abnormal cristae morphology. Thus, Opa1 is a key factor in osteoclast differentiation through regulation of mitochondrial dynamics.

N6-methyladenosine demethylase FTO promotes growth and metastasis of gastric cancer via m6A modification of caveolin-1 and metabolic regulation of mitochondrial dynamics

Gastric cancer (GC) is the fifth most common tumor and the third most deadly cancer worldwide. N6-methyladenosine (m6A) modification has been reported to play a regulatory role in human cancers. However, the exact role of m6A in GC remains largely unknown, and the dysregulation of m6A on mitochondrial metabolism has never been studied. In the present study, we demonstrated that FTO, a key demethylase for RNA m6A modification, was up-regulated in GC tissues, especially in tissues with liver metastasis. Functionally, FTO acted as a promoter for the proliferation and metastasis in GC. Moreover, FTO enhanced the degradation of caveolin-1 mRNA via its demethylation, which regulated the mitochondrial fission/fusion and metabolism. Collectively, our current findings provided some valuable insights into FTO-mediated m6A demethylation modification and could be used as a new strategy for more careful surveillance and aggressive therapeutic intervention.

Melatonin and verteporfin synergistically suppress the growth and stemness of head and neck squamous cell carcinoma through the regulation of mitochondrial dynamics.

The prevalence of head and neck squamous cell carcinoma (HNSCC) has continued to rise for decades. However, drug resistance to chemotherapeutics and relapse, mediated by cancer stem cells (CSCs), remains a significant impediment in clinical oncology to achieve successful treatment. Therefore, we focused on analyzing CSCs in HNSCC and demonstrated the effect of melatonin (Mel) and verteporfin (VP) on SCC-25 cells. HNSCC CSCs were enriched in the reactive oxygen species-low state and in sphere-forming cultures. Combination treatment with Mel and VP decreased HNSCC viability and increased apoptosis without causing significant damage to normal cells. Sphere-forming ability and stem cell population were reduced by co-treatment with Mel and VP, while mitochondrial ROS level was increased by the treatment. Furthermore, the expression of mitophagy markers, parkin and PINK1, was significantly decreased in the co-treated cells. Mel and VP induced mitochondrial depolarization and inhibited mitochondrial function. Parkin/TOM20 was localized near the nucleus and formed clusters of mitochondria in the cells after treatment. Moreover, Mel and VP downregulated the expression of markers involved in epithelial-mesenchymal transition and metastasis. The migration capacity of cells was significantly decreased by co-treatment with Mel and VP, accompanied by the down-regulation of MMP-2 and MMP-9 expression. Taken together, these results indicate that co-treatment with Mel and VP induces mitochondrial dysfunction, resulting in the apoptosis of CSCs. Mel and VP could thus be further investigated as potential therapies for HNSCC through their action on CSCs.

Neuroinflammation-mediated mitochondrial dysregulation involved in postoperative cognitive dysfunction

Neuroinflammation following peripheral surgery is a pivotal pathogenic mechanism of postoperative cognitive dysfunction (POCD). However, the key site of inflammation-mediated neural damage remains unclear. Impaired mitochondrial function is a vital feature of degenerated neurons. Dynamin-related protein 1 (DRP1), a crucial regulator of mitochondrial dynamics, has been shown to play an essential role in synapse formation. Here, we designed experiments to assess whether Drp1-regulated mitochondrial dynamics and function are involved in the pathological processes of POCD and elucidate its relationship with neuroinflammation. Aged mice were subjected to experimental laparotomy under isoflurane anesthesia. Primary neurons and SH-SY5Y cells were exposed to tumor necrosis factor (TNF). We found an increase in Drp1 activation as well as mitochondrial fragmentation both in the hippocampus of mice after surgery and primary neurons after TNF exposure. Pretreatment with Mdivi-1, a Drp1 specific inhibitor, reduced this mitochondrial fragmentation. Drp1 knockdown with small interfering RNA blocked TNF-induced mitochondrial fragmentation in SH-SY5Y cells. However, the application of Mdivi-1 exhibited a negative impact on mitochondrial function and neurite growth in primary neurons. Calcineurin activity was increased in primary neurons after TNF exposure and contributed to the Drp1 activation. The calcineurin inhibitor FK506 exhibited a Drp1-independent function that mitigated mitochondrial dysfunction. Finally, we found that FK506 pretreatment ameliorated the neurite growth in neurons treated with TNF and the learning ability of mice after surgery. Overall, our research indicated a crucial role of mitochondrial function in the pathological processes of POCD, and neuronal metabolic modulation may represent a novel and important target for POCD.

The balance of mitochondrial fission and fusion in cortical axons depends on the kinases SadA and SadB.

Neurons are highly polarized cells that display characteristic differences in the organization of their organelles in axons and dendrites. The kinases SadA and SadB (SadA/B) promote the formation of distinct axonal and dendritic extensions during the development of cortical and hippocampal neurons. Here, we show that SadA/B are required for the specific dynamics of axonal mitochondria. Ankyrin B (AnkB) stimulates the activity of SadA/B that function as regulators of mitochondrial dynamics through the phosphorylation of tau. Suppression of SadA/B or AnkB in cortical neurons induces the elongation of mitochondria by disrupting the balance of fission and fusion. SadA/B-deficient neurons show an accumulation of hyper-fused mitochondria and activation of the integrated stress response (ISR). The normal dynamics of axonal mitochondria could be restored by mild actin destabilization. Thus, the elongation after loss of SadA/B results from an excessive stabilization of actin filaments and reduction of Drp1 recruitment to mitochondria.

First person – Shruti Patrick

ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Shruti Patrick is first author on ‘ YAP1-mediated regulation of mitochondrial dynamics in IDH1 mutant gliomas’, published in JCS. Shruti is a PhD student in the lab of Ellora Sen at National Brain Research Centre, Haryana, India, investigating the differential roles of potential therapeutic targets in the context of IDH1 wild-type and IDH1 mutant gliomas.

The Multifaceted Regulation of Mitochondrial Dynamics During Mitosis.

Mitosis ensures genome integrity by mediating precise segregation of the duplicated genetic material. Segregation of subcellular organelles during mitosis also needs to be tightly coordinated in order to warrant their proper inheritance and cellular homeostasis. The inheritance of mitochondria, a powerhouse of the cell, is tightly regulated in order to meet the high energy demand to fuel the mitotic machinery. Mitochondria are highly dynamic organelles, which undergo events of fission, fusion and transport during different cell cycle stages. Importantly, during mitosis several kinases phosphorylate the key mitochondrial factors and drive fragmentation of mitochondria to allow for their efficient distribution and inheritance to two daughter cells. Recent evidence suggests that mitochondrial fission can also actively contribute to the regulation of mitotic progression. This review aims at summarizing established and emerging concepts about the complex regulatory networks which couple crucial mitotic factors and events to mitochondrial dynamics and which could be implicated in human disease.

Regulation of mitochondrial fission by GIPC-mediated Drp1 retrograde transport.

Dynamin-related protein 1 (Drp1) is a key regulator of mitochondrial fission, a large cytoplasmic GTPase recruited to the mitochondrial surface via transmembrane adaptors to initiate scission. While Brownian motion likely accounts for the local interactions between Drp1 and the mitochondrial adaptors, how this essential enzyme is targeted from more distal regions like the cell periphery remains unknown. Based on proteomic interactome screening and cell-based studies, we report that GAIP/RGS19-interacting protein (GIPC) mediates the actin-based retrograde transport of Drp1 toward the perinuclear mitochondria to enhance fission. Drp1 interacts with GIPC through its atypical C-terminal PDZ-binding motif. Loss of this interaction abrogates Drp1 retrograde transport resulting in cytoplasmic mislocalization and reduced fission despite retaining normal intrinsic GTPase activity. Functionally, we demonstrate that GIPC potentiates the Drp1-driven proliferative and migratory capacity in cancer cells. Together, these findings establish a direct molecular link between altered GIPC expression and Drp1 function in cancer progression and metabolic disorders.

The structural organization and functions of the ERMES complex in fungi

<p indent=0mm>In eukaryotic cells, mitochondria, the double-membrane bound organelle, form different networks by undergoing constant fission and fusion to meet the changing energy demands. The proper function of mitochondria and the regulation of mitochondrial dynamics depend on the proper contact of mitochondria with other subcellular organelles and the materials exchanged between the two contacting organelles. Mitochondria form contact sites with many organelles including lipid droplets, peroxisomes, vacuoles, and the endoplasmic reticulum (ER). The ER-mitochondria encounter structure (ERMES) mediates the contact between the ER and mitochondria and plays important roles in regulating mitochondrial morphology and functions. Malfunctions of the ERMES complex affect mitochondrial dynamics, calcium signalling, lipid transport, drug resistance and tolerance in fungi, and the virulence of pathogenic fungi. In this review, we discuss the structural organization, functions, and the regulation of the ERMES complex.

Study of long non-coding RNA and mitochondrial dysfunction in diabetic rats

Abstract Diabetes mellitus (DM) is a worldwide health problem. Many factors participate in the pathogenesis of DM, including genetic, autoimmune, metabolic, dietary and environmental factors. Intact mitochondrial function is essential for prompt cellular metabolism and energy balance. Malfunctioning mitochondria lead to disturbed glucose metabolism and therefore evolving of DM. Epigenetics plays a role in the control of geneencoded proteins of mitochondrial function and dynamics. One of the primary epigenetic effectors is a family of long non-coding RNAs. The role of lncRNA, H19 in the regulation of mitochondrial dynamics has been recently investigated. The Aim of the work This study aims to evaluate the possible functional role of lncRNA, H19 and its relation to mitofusin-2 (MFN2) expression in diabetic rats. Subjects and methods This study was performed on adult male albino rats divided into diabetic and control groups. Induction of type 1 DM was conducted through single intraperitoneal injection of streptozotocin. Serum measurement of glucose, lipid profile, urea, creatinine, and creatine kinase were performed. Blood pressure measurement, ECG recording, and echocardiography were also performed. Histological examination of cardiac and renal tissues was also performed. In addition, quantitative expression of cardiac and renal tissue MFN2 and lncRNA H19 was determined using qPCR. Results Serum CK-MB and lipid profile levels were markedly elevated in diabetic group compared to controls. Also, kidney functions (serum creatinine, creatinine clearance and albumin creatinine ratio) were markedly elevated in diabetic group compared to controls. Histological examination revealed necrotic changes and intercellular micro hemorrhages in both cardiac and renal tissues of diabetic rats. Expression level of MFN2 gene was lower in diabetic heart and significantly lower in diabetic kidney, as compared to control. Expression of lncRNA H19 was higher in diabetic heart and diabetic kidney as compared to control but without statistical significance. Conclusion In diabetic rats, hyperglycemia had inverse relationship with mitofusin expression and direct proportional relationship with H19 expression. We concluded that hyperglycemia has effect on mitochondrial dynamics suppressing fusion in favor of fission and mitophagy, while H19 expression serve to counterpart the effect of hyperglycemia. In the future, MFN and H19 could serve as potential therapeutic target to reverse effects of hyperglycemia and its complications in DM.

Cardioprotective effect of ethanol extracts of Sugemule-3 decoction on isoproterenol-induced heart failure in Wistar rats through regulation of mitochondrial dynamics

Sugemule-3 decoction (SD-3) is a commonly used prescription in Mongolian medicine which composed of the herbs Baidoukou (the fruit of Amomum compactum Sol. ex Maton), Baijusheng (the fruit of Lactuca sativa L.) and Biba (Piper longum L.). SD-3 has remarkable effect on the cardiovascular diseases, but its pharmacological mechanism has not been elucidated. To evaluate the cardioprotective effects and the potential mechanisms of the ethanol extracts of SD-3 against isoproterenol (ISO)-induced heart failure (HF) in rats. The ethanol extracts of SD-3 were prepared and analyzed by LC-ESI-MS/MS. One hundred male Wistar rats were randomly divided into five groups: control, ISO (HF) and different doses of SD-3 (0.4, 0.2, 0.1g/kg/d) groups. HF model rats were established by intraperitoneal injecting of ISO. The left ventricular function was evaluated by echocardiography. Myocardial injury and fibrosis were examined by hematoxylin-eosin (HE) and Masson staining. Western-blot analysis was performed to determine the protein expression of apoptosis and mitochondrial dynamics in all the groups. Moreover, the structural changes in the mitochondria of cardiomyocytes were also observed by transmission electron microscopy. Fifteen compounds were detected in the ethanol extracts of SD-3, include piperine, piperanine, etc. Rats administered with ISO showed a significant decline in the left ventricular function. The cardiac histopathological changes such as local necrosis, interstitial edema, and cardiac fibrosis were also observed in the ISO group. The treatment with SD-3 significantly inhibited these effects of ISO. ISO was found to increase the protein expression of Bax, cleaved-PARP and cleaved-caspase-3, -7 -9, destroy the balance between mitochondrial fusion and fission, and alter the mitochondrial morphology. The ethanol extracts of SD-3 could rebalance mitochondrial fusion and fission, and ameliorates the morphological abnormalities induced by ISO in mitochondria. The current study demonstrated that ethanol extracts of SD-3 improved isoprenaline-induced cardiac hypertrophy and fibrosis through inhibiting cardiomyocyte apoptosis and regulating the mitochondrial dynamics.

Dynamin-related protein 1 regulates substrate oxidation in skeletal muscle by stabilizing cellular and mitochondrial calcium dynamics

Mitochondria undergo continuous cycles of fission and fusion to promote inheritance, regulate quality control, and mitigate organelle stress. More recently, this process of mitochondrial dynamics has been demonstrated to be highly sensitive to nutrient supply, ultimately conferring bioenergetic plasticity to the organelle. However, whether regulators of mitochondrial dynamics play a causative role in nutrient regulation remains unclear. In this study, we generated a cellular loss-of-function model for dynamin-related protein 1 (DRP1), the primary regulator of outer membrane mitochondrial fission. Loss of DRP1 (shDRP1) resulted in extensive ultrastructural and functional remodeling of mitochondria, characterized by pleomorphic enlargement, increased electron density of the matrix, and defective NADH and succinate oxidation. Despite increased mitochondrial size and volume, shDRP1 cells exhibited reduced cellular glucose uptake and mitochondrial fatty acid oxidation. Untargeted transcriptomic profiling revealed severe downregulation of genes required for cellular and mitochondrial calcium homeostasis, which was coupled to loss of ATP-stimulated calcium flux and impaired substrate oxidation stimulated by exogenous calcium. The insights obtained herein suggest that DRP1 regulates substrate oxidation by altering whole-cell and mitochondrial calcium dynamics. These findings are relevant to the targetability of mitochondrial fission and have clinical relevance in the identification of treatments for fission-related pathologies such as hereditary neuropathies, inborn errors in metabolism, cancer, and chronic diseases.

Redox-Mediated Regulation of Mitochondrial Biogenesis, Dynamics, and Respiratory Chain Assembly in Yeast and Human Cells.

Mitochondria are double-membrane organelles that contain their own genome, the mitochondrial DNA (mtDNA), and reminiscent of its endosymbiotic origin. Mitochondria are responsible for cellular respiration via the function of the electron oxidative phosphorylation system (OXPHOS), located in the mitochondrial inner membrane and composed of the four electron transport chain (ETC) enzymes (complexes I-IV), and the ATP synthase (complex V). Even though the mtDNA encodes essential OXPHOS components, the large majority of the structural subunits and additional biogenetical factors (more than seventy proteins) are encoded in the nucleus and translated in the cytoplasm. To incorporate these proteins and the rest of the mitochondrial proteome, mitochondria have evolved varied, and sophisticated import machineries that specifically target proteins to the different compartments defined by the two membranes. The intermembrane space (IMS) contains a high number of cysteine-rich proteins, which are mostly imported via the MIA40 oxidative folding system, dependent on the reduction, and oxidation of key Cys residues. Several of these proteins are structural components or assembly factors necessary for the correct maturation and function of the ETC complexes. Interestingly, many of these proteins are involved in the metalation of the active redox centers of complex IV, the terminal oxidase of the mitochondrial ETC. Due to their function in oxygen reduction, mitochondria are the main generators of reactive oxygen species (ROS), on both sides of the inner membrane, i.e., in the matrix and the IMS. ROS generation is important due to their role as signaling molecules, but an excessive production is detrimental due to unwanted oxidation reactions that impact on the function of different types of biomolecules contained in mitochondria. Therefore, the maintenance of the redox balance in the IMS is essential for mitochondrial function. In this review, we will discuss the role that redox regulation plays in the maintenance of IMS homeostasis as well as how mitochondrial ROS generation may be a key regulatory factor for ETC biogenesis, especially for complex IV.