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OXPHOS deficiency activates global adaptations to maintain mitochondrial membrane potential

ABSTRACT: Reduction of mitochondrial membrane potential is a hallmark of mitochondrial dysfunction. It activates adaptive responses in organisms from yeast to human to rewire metabolism, remove depolarized mitochondria, and degrade unimported precursor proteins. It remains unclear how cells maintain mitochondrial membrane potential, which is critical for maintaining iron-sulfur cluster (ISC) synthesis, an indispensable function of mitochondria. Here we show that yeast oxidative phosphorylation mutants deficient in complex III, IV, V, and mtDNA respectively, have graded reduction of mitochondrial membrane potential and proliferation rates. Extensive omics analyses of these mutants show that accompanying mitochondrial membrane potential reduction, these mutants progressively activate adaptive responses, including transcriptional downregulation of ATP synthase inhibitor Inh1 and OXPHOS subunits, Puf3-mediated upregulation of import receptor Mia40 and global mitochondrial biogenesis, Snf1/AMPK-mediated upregulation of glycolysis and repression of ribosome biogenesis, and transcriptional upregulation of cytoplasmic chaperones. These adaptations disinhibit mitochondrial ATP hydrolysis, remodel mitochondrial proteome, and optimize ATP supply to mitochondria to convergently maintain mitochondrial membrane potential, ISC biosynthesis, and cell proliferation.

INSTRUMENT(S): LTQ Orbitrap Velos, Q Exactive

ORGANISM(S): Saccharomyces Cerevisiae (baker's Yeast)

SUBMITTER: Siqi Liu

LAB HEAD: Hui Jiang

PROVIDER: PXD022805 | Pride | 2021-01-19

REPOSITORIES: Pride

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Project description:Background. Bacillus subtilis is a favorable host for the production of industrially relevant proteins because of its capacity of secreting proteins into the medium to high levels, its GRAS (Generally Recognized As Safe) status, its genetic accessibility and its capacity to grow in large fermentations. However, production of heterologous proteins still faces limitations. Results. This study aimed at the identification of bottlenecks in secretory protein production by analyzing the response of B. subtilis at the transcriptome level to overproduction of eight secretory proteins of endogenous and heterologous origin and with different subcellular or extracellular destination: secreted proteins (NprE and XynA of B. subtilis, Usp45 of Lactococcus lactis, TEM-1beta -lactamase of Escherichia coli), membrane proteins (LmrA of L. lactis and XylP of Lactobacillus pentosus) and lipoproteins (MntA and YcdH of B. subtilis). Responses specific for proteins with a common localization as well as more general stress responses were observed. The latter include upregulation of genes encoding intracellular stress proteins (groES/EL, CtsR regulated genes). Specific responses include upregulation of the liaIHGFSR operon under Usp45 and TEM-1 beta-lactamase overproduction; cssRS, htrA and htrB under all secreted proteins overproduction; sigW and SigW-regulated genes mainly under membrane proteins overproduction; and ykrL (encoding an HtpX homologue) specifically under membrane proteins overproduction. Conclusions. The results give better insights into B. subtilis responses to protein overproduction stress and provide potential targets for genetic engineering in order to further improve B. subtilis as a protein production host. Samples for transcriptome analyses were induced at the exponential-growth phase (OD600 = 0.7) with 0.1% subtilin (subtilin containing supernatant of subtilin producing B. subtilis strain ATCC 6633). Cells were harvested 30 min after induction. Three or four independent cultures of each strain (target strains and controls) were used, and cells were sampled for microarray experiment.

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OXPHOS deficiency activates global adaptations to maintain mitochondrial membrane potential

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