Scaf1 promotes respiratory supercomplexes and metabolic efficiency in zebrafish

The oxidative phosphorylation (OXPHOS) system is a dynamic system in which the respiratory complexes coexist with superassembled quaternary structures called supercomplexes (SCs). The physiological role of SCs is still disputed. Here, we used zebrafish to study the relevance of respiratory SCs. We combined immunodetection analysis and deep data-independent proteomics to characterize these structures and found similar SCs to those described in mice, as well as novel SCs including III2 + IV2, I + IV, and I + III2 + IV2. To study the physiological role of SCs, we generated two null allele zebrafish lines for supercomplex assembly factor 1 (scaf1). scaf1 / fish displayed altered OXPHOS activity due to the disrupted interaction of complexes III and IV. scaf1 / fish were smaller in size and showed abnormal fat deposition and decreased female fertility. These physiological phenotypes were rescued by doubling the food supply, which correlated with improved bioenergetics and alterations in the metabolic gene expression program. These results reveal that SC assembly by Scaf1 modulates OXPHOS efficiency and allows the optimization of metabolic resources.Microscopy Imaging Center of the University of BernSpanish Ministry of Economy and Competitiveness, MINECO SAF2015-65633-RSpanish Ministry of Economy and Competitiveness, MINECO SAF2015-65633-RHuman Frontier Science Program RGP0016/2018European Research Council (ERC) 337703SNF 31003A-159721Swiss National Science Foundation (SNSF) 320030_170062MINECO BIO2015-67580-PCarlos III Institute of Health-Fondo de Investigacion Sanitaria) PRB3 IPT17/0019Fundacion La Marato TV3La Caixa Foundation HR17-00247Ministry of Economy, Industry and Competitiveness (MEIC)Pro-CNIC FoundationSevero Ochoa Center of Excellence (MEIC award) SEV-2015-050

The APPswe/PS1A246E mutations in an astrocytic cell line leads to increased vulnerability to oxygen and glucose deprivation, Ca2+ dysregulation and mitochondrial abnormalities

Growing evidence suggests a close relationship between Alzheimer's Disease (AD) and cerebral hypoxia. Astrocytes play a key role in brain homeostasis and disease states, while some of the earliest changes in AD occur in astrocytes. We have therefore asked whether mutations associated with AD increase astrocyte vulnerability to ischemia. Two astroglioma cell lines derived from APPSWE /PS1A246E (APP, amyloid precursor protein; PS1, presenilin 1) transgenic mice and controls from normal mice were subjected to oxygen and glucose deprivation (OGD), an in vitro model of ischemia. Cell death was increased in the APPSWE /PS1A246E line compared to the control. Increasing extracellular calcium concentration ([Ca2+ ]) exacerbated cell death in the mutant but not in the control cells. In order to explore cellular Ca2+ homeostasis the cells were challenged with ATP or thapsigargin and [Ca2+ ] was measured by fluorescence microscopy. Changes in cytosolic Ca2+ concentration ([Ca2+ ]c ) were potentiated in the APPSWE /PS1A246E transgenic line. Mitochondrial function was also altered in the APPSWE /PS1A246E astroglioma cells; mitochondrial membrane potential and production of reactive oxygen species were increased while mitochondrial basal respiratory rate and ATP production were decreased compared to control astroglioma cells. These results suggest that AD mutations in astrocytes make them more sensitive to ischemia; Ca2+ dysregulation and mitochondrial dysfunction may contribute to this increased vulnerability. Our results also highlight the role of astrocyte dyshomeostasis in the pathophysiology of neurodegenerative brain disorders

Role of Mitochondrial Complex IV in Age-Dependent Obesity

Aging is associated with progressive white adipose tissue (WAT) enlargement initiated early in life, but the molecular mechanisms involved remain unknown. Here we show that mitochondrial complex IV (CIV) activity and assembly are already repressed in white adipocytes of middle-aged mice and involve a HIF1A-dependent decline of essential CIV components such as COX5B. At the molecular level, HIF1A binds to the Cox5b proximal promoter and represses its expression. Silencing of Cox5b decreased fatty acid oxidation and promoted intracellular lipid accumulation. Moreover, local in vivo Cox5b silencing in WAT of young mice increased the size of adipocytes, whereas restoration of COX5B expression in aging mice counteracted adipocyte enlargement. An age-dependent reduction in COX5B gene expression was also found in human visceral adipose tissue. Collectively, our findings establish a pivotal role for CIV dysfunction in progressive white adipocyte enlargement during aging, which can be restored to alleviate age-dependent WAT expansion

Corrigendum to "European contribution to the study of ROS:A summary of the findings and prospects for the future from the COST action BM1203 (EU-ROS)" [Redox Biol. 13 (2017) 94-162]

The European Cooperation in Science and Technology (COST) provides an ideal framework to establish multi-disciplinary research networks. COST Action BM1203 (EU-ROS) represents a consortium of researchers from different disciplines who are dedicated to providing new insights and tools for better understanding redox biology and medicine and, in the long run, to finding new therapeutic strategies to target dysregulated redox processes in various diseases. This report highlights the major achievements of EU-ROS as well as research updates and new perspectives arising from its members. The EU-ROS consortium comprised more than 140 active members who worked together for four years on the topics briefly described below. The formation of reactive oxygen and nitrogen species (RONS) is an established hallmark of our aerobic environment and metabolism but RONS also act as messengers via redox regulation of essential cellular processes. The fact that many diseases have been found to be associated with oxidative stress established the theory of oxidative stress as a trigger of diseases that can be corrected by antioxidant therapy. However, while experimental studies support this thesis, clinical studies still generate controversial results, due to complex pathophysiology of oxidative stress in humans. For future improvement of antioxidant therapy and better understanding of redox-associated disease progression detailed knowledge on the sources and targets of RONS formation and discrimination of their detrimental or beneficial roles is required. In order to advance this important area of biology and medicine, highly synergistic approaches combining a variety of diverse and contrasting disciplines are needed

Na+ controls hypoxic signalling by the mitochondrial respiratory chain

This is the collection for the source data in the article "Na+ controls hypoxic signalling by the mitochondrial respiratory chain

Reactive oxygen species, nutrition, hypoxia and diseases: Problems solved?

Within the last twenty years the view on reactive oxygen species (ROS) has changed; they are no longer only considered to be harmful but also necessary for cellular communication and homeostasis in different organisms ranging from bacteria to mammals. In the latter, ROS were shown to modulate diverse physiological processes including the regulation of growth factor signaling, the hypoxic response, inflammation and the immune response. During the last 60-100 years the life style, at least in the Western world, has changed enormously. This became obvious with an increase in caloric intake, decreased energy expenditure as well as the appearance of alcoholism and smoking; These changes were shown to contribute to generation of ROS which are, at least in part, associated with the occurrence of several chronic diseases like adiposity, atherosclerosis, type II diabetes, and cancer. In this review we discuss aspects and problems on the role of intracellular ROS formation and nutrition with the link to diseases and their problematic therapeutical issues

Reactive oxygen species, nutrition, hypoxia and diseases:problems solved?

Abstract Within the last twenty years the view on reactive oxygen species (ROS) has changed; they are no longer only considered to be harmful but also necessary for cellular communication and homeostasis in different organisms ranging from bacteria to mammals. In the latter, ROS were shown to modulate diverse physiological processes including the regulation of growth factor signaling, the hypoxic response, inflammation and the immune response. During the last 60–100 years the life style, at least in the Western world, has changed enormously. This became obvious with an increase in caloric intake, decreased energy expenditure as well as the appearance of alcoholism and smoking; These changes were shown to contribute to generation of ROS which are, at least in part, associated with the occurrence of several chronic diseases like adiposity, atherosclerosis, type II diabetes, and cancer. In this review we discuss aspects and problems on the role of intracellular ROS formation and nutrition with the link to diseases and their problematic therapeutical issues

Na+ controls hypoxic signalling by the mitochondrial respiratory chain

All metazoans depend on O2 delivery and consumption by the mitochondrial oxidative phosphorylation (OXPHOS) system to produce energy. A decrease in O2 availability (hypoxia) leads to profound metabolic rewiring. In addition, OXPHOS uses O2 to produce reactive oxygen species (ROS) that can drive cell adaptations through redox signalling, but also trigger cell damage1–4, and both phenomena occur in hypoxia4–8. However, the precise mechanism by which acute hypoxia triggers mitochondrial ROS production is still unknown. Ca2+ is one of the best known examples of an ion acting as a second messenger9, yet the role ascribed to Na+ is to serve as a mere mediator of membrane potential and collaborating in ion transport10. Here we show that Na+ acts as a second messenger regulating OXPHOS function and ROS production by modulating fluidity of the inner mitochondrial membrane (IMM). We found that a conformational shift in mitochondrial complex I during acute hypoxia11 drives the acidification of the matrix and solubilization of calcium phosphate precipitates. The concomitant increase in matrix free-Ca2+ activates the mitochondrial Na+/Ca2+ exchanger (NCLX), which imports Na+ into the matrix. Na+ interacts with phospholipids reducing IMM fluidity and mobility of free ubiquinone between complex II and complex III, but not inside supercomplexes. As a consequence, superoxide is produced at complex III, generating a redox signal. Inhibition of mitochondrial Na+ import through NCLX is sufficient to block this pathway, preventing adaptation to hypoxia. These results reveal that Na+ import into the mitochondrial matrix controls OXPHOS function and redox signalling through an unexpected interaction with phospholipids, with profound consequences in cellular metabolism

Corrigendum to “European contribution to the study of ROS: A summary of the findings and prospects for the future from the COST action BM1203 (EU-ROS)” (Redox Biol. (2017) 13 (94–162)(S2213231717303373)(10.1016/j.redox.2017.05.007))

The authors regret that they have to correct the acknowledgement of the above mentioned publication as follows: This article/publication is based upon work from COST Action BM1203 (EU-ROS), supported by COST (European Cooperation in Science and Technology) which is funded by the Horizon 2020 Framework Programme of the European Union. COST (European Cooperation in Science and Technology) is a funding agency for research and innovation networks. Our Actions help connect research initiatives across Europe and enable scientists to grow their ideas by sharing them with their peers. This boosts their research, career and innovation. For further information see www.cost.eu. The authors would like to apologise for any inconvenience caused.This article/publication is based upon work from COST Action BM1203 (EU-ROS), supported by COST (European Cooperation in Science and Technology) which is funded by the Horizon 2020 Framework Programme of the European Union. COST (European Cooperation in Science and Technology) is a funding agency for research and innovation networks