bims-resufa 2020-08-30 papers

Issue of 2020–08–30
three papers selected by
Vera Strogolova, Marquette University

Biochim Biophys Acta Mol Basis Dis. 2020 Aug 19. pii: S0925-4439(20)30283-0. [Epub ahead of print] 165935

Alteration of mitochondrial supercomplexes assembly in metabolic diseases.

I Ramírez-Camacho, W R García-Niño, M Flores-García, J Pedraza-Chaverri, C Zazueta.

Deregulation of nutrient, hormonal, or neuronal signaling produces metabolic alterations that result in increased mitochondrial reactive oxygen species (ROS) production. The associations of the mitochondrial respiratory chain components into supercomplexes could have pathophysiological relevance in metabolic diseases, as supramolecular arrangements, by sustaining a high electron transport rate, might prevent ROS generation. In this review, the relationship between mitochondrial dysfunction and supercomplex arrangement of the mitochondrial respiratory chain components in obesity, insulin resistance, hepatic steatosis and diabetes mellitus is summarized and discussed.

Keywords: Insulin resistance; Liver; Obesity; Respiratory supercomplexes; T2DM

DOI: https://doi.org/10.1016/j.bbadis.2020.165935

Methods Mol Biol. 2021 ;2202 81-91

Fluorescence Detection of Increased Reactive Oxygen Species Levels in Saccharomyces cerevisiae at the Diauxic Shift.

Abhishek Sinha, Elah Pick.

The budding yeast Saccharomyces cerevisiae is a facultative organism that is able to utilize both anaerobic and aerobic metabolism, depending on the composition of carbon source in the growth medium. When glucose is abundant, yeast catabolizes it to ethanol and other by-products by anaerobic fermentation through the glycolysis pathway. Following glucose exhaustion, cells switch to oxygenic respiration (a.k.a. "diauxic shift"), which allows catabolizing ethanol and the other carbon compounds via the TCA cycle and oxidative phosphorylation in the mitochondria. The diauxic shift is accompanied by elevated reactive oxygen species (ROS) levels and is characterized by activation of ROS defense mechanisms. Traditional measurement of the diauxic shift is done through measuring optical density of cultures grown in a batch at intermediate time points and generating a typical growth curve or by estimating the reduction of glucose and accumulation of ethanol in growth media over time. In this manuscript, we describe a method for determining changes in ROS levels upon yeast growth, using carboxy-H(2)-dichloro-dihydrofluorescein diacetate (carboxy-H(2)-DCFDA). H2-DCFDA is a widely used fluorescent dye for measuring intracellular ROS levels. H2-DCFDA enables a direct measurement of ROS in yeast cells at intermediate time points. The outcome of H2-DCFDA fluorescent readout measurements correlates with the growth curve information, hence providing a clear understanding of the diauxic shift.

Keywords: Diauxic shift; Fermentation; Oxidative stress; Reactive oxygen species (ROS); Respiration; Saccharomyces cerevisiae

DOI: https://doi.org/10.1007/978-1-0716-0896-8_7

Front Plant Sci. 2020 ;11 1177

Potential Pathway of Nitrous Oxide Formation in Plants.

Arbindra Timilsina, Chuang Zhang, Bikram Pandey, Fiston Bizimana, Wenxu Dong, Chunsheng Hu.

Plants can produce and emit nitrous oxide (N2O), a potent greenhouse gas, into the atmosphere, and several field-based studies have concluded that this gas is emitted at substantial amounts. However, the exact mechanisms of N2O production in plant cells are unknown. Several studies have hypothesised that plants might act as a medium to transport N2O produced by soil-inhabiting microorganisms. Contrarily, aseptically grown plants and axenic algal cells supplied with nitrate (NO3) are reported to emit N2O, indicating that it is produced inside plant cells by some unknown physiological phenomena. In this study, the possible sites, mechanisms, and enzymes involved in N2O production in plant cells are discussed. Based on the experimental evidence from various studies, we determined that N2O can be produced from nitric oxide (NO) in the mitochondria of plants. NO, a signaling molecule, is produced through oxidative and reductive pathways in eukaryotic cells. During hypoxia and anoxia, NO3 in the cytosol is metabolised to produce nitrite (NO2), which is reduced to form NO via the reductive pathway in the mitochondria. Under low oxygen condition, NO formed in the mitochondria is further reduced to N2O by the reduced form of cytochrome c oxidase (CcO). This pathway is active only when cells experience hypoxia or anoxia, and it may be involved in N2O formation in plants and soil-dwelling animals, as reported previously by several studies. NO can be toxic at a high concentration. Therefore, the reduction of NO to N2O in the mitochondria might protect the integrity of the mitochondria, and thus, protect the cell from the toxicity of NO accumulation under hypoxia and anoxia. As NO3 is a major source of nitrogen for plants and all plants may experience hypoxic and anoxic conditions owing to soil environmental factors, a significant global biogenic source of N2O may be its formation in plants via the proposed pathway.

Keywords: anoxia; hypoxia; mitochondrion; nitrate; nitric oxide; nitrite; nitrous oxide

DOI: https://doi.org/10.3389/fpls.2020.01177