Natural tetramic acids elicit multiple inhibitory actions against mitochondrial machineries presiding over oxidative phosphorylation

The mitochondrial machineries presiding over ATP synthesis via oxidative phosphorylation are promising druggable targets. Fusaramin, a 3-acyl tetramic acid isolated from Fusarium concentricum FKI-7550, is an inhibitor of oxidative phosphorylation in Saccharomyces cerevisiae mitochondria, although its target has yet to be identified. Fusaramin significantly interfered with [3H]ADP uptake by yeast mitochondria at the concentration range inhibiting oxidative phosphorylation. A photoreactive fusaramin derivative (pFS-5) specifically labeled voltage-dependent anion channel 1 (VDAC1), which facilitates trafficking of ADP/ATP across the outer mitochondrial membrane. These results strongly suggest that the inhibition of oxidative phosphorylation by fusaramin is predominantly attributable to the impairment of VDAC1 functions. Fusaramin also inhibited FoF1-ATP synthase and ubiquinol-cytochrome c oxidoreductase (complex III) at concentrations higher than those required for the VDAC inhibition. Considering that other tetramic acid derivatives are reported to inhibit FoF1-ATP synthase and complex III, natural tetramic acids were found to elicit multiple inhibitory actions against mitochondrial machineries.

The Regulation of Non-Specific Membrane Permeability Transition in Yeast Mitochondria under Oxidative Stress

In this study, the mechanism of non-specific membrane permeability (yPTP) in the Endomyces magnusii yeast mitochondria under oxidative stress due to blocking the key antioxidant enzymes has been investigated. We used monitoring the membrane potential at the cellular (potential-dependent staining) and mitochondrial levels and mitochondria ultra-structural images with transmission electron microscopy (TEM) to demonstrate the mitochondrial permeability transition induction due to the pore opening. Analysis of the yPTP opening upon respiring different substrates showed that NAD(P)H completely blocked the development of the yPTP. The yPTP opening was inhibited by 5–20 mM Pi, 5 mM Mg2+, adenine nucleotides (AN), 5 mM GSH, the inhibitor of the Pi transporter (PiC), 100 μM mersalyl, the blockers of the adenine nucleotide transporter (ANT) carboxyatractyloside (CATR), and bongkrekic acid (BA). We concluded that the non-specific membrane permeability pore opens in the E. magnusii mitochondria under oxidative stress, and the ANT and PiC are involved in its formation. The crucial role of the Ca2+ ions in the process has not been confirmed. We showed that the Ca2+ ions affected the yPTP both with and without the Ca2+ ionophore ETH129 application insignificantly. This phenomenon in the E. magnusii yeast unites both mitochondrial unselective channel (ScMUC) features in the Saccharomyces cerevisiae mitochondria and the classical membrane pore in the mammalian ones (mPTP).

Non-respiratory functions of Saccharomyces cerevisiae mitochondria are required for optimal attractiveness to Drosophila melanogaster

While screening a large collection of wild and laboratory yeast isolates for their ability to attract Drosophila melanogaster adults, we noticed a large difference in fly preference for two nearly isogenic strains of Saccharomyces cerevisiae, BY4741 and BY4742. Using standard genetic analyses, we tracked the preference difference to the lack of functional mitochondria the stock of BY4742 used in the initial experiment. We used gas chromatography coupled with mass spectroscopy to examine the volatile compounds produced by BY4741 and the mitochondria-deficient BY4742, and found they differed significantly. We found that several ethyl esters are present at much higher levels in strains with functional mitochondria, even in fermentative conditions. We confirmed the role of these ethyl esters in attraction by examining an EEB1Δ strain which reduces ethyl ester production. We found that nitrogen levels in the substrate affect the production of these compounds, and that they are produced at high levels by strains with functional mitochondria in the fermentation of natural substrates. Collectively these observations demonstrate the effect core metabolic processes have in mediating the interaction between yeasts and insect vectors, and highlight the importance of non-respirative mitochondrial functions in yeast ecology.