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Ketogenesis: An Achilles' heel of starvation-selected persistent mycobacteria

ABSTRACT: Mycobacterial pathogens adapt to environmental stresses such as nutrient deprivation by entering a non-replicative antibiotic-tolerant state of persistence. Using a biochemically-validated data-driven approach, we identified an adaptive metabolic network underlying the mycobacterial response to starvation in M. tuberculosis, M. bovis BCG and M. smegmatis. All three species show a strong Mg+2-dependence for surviving complete nutrient deprivation, accompanied by a broad phenotypic antibiotic resistance. Multivariate analysis of RNA-seq, metabolic phenotyping and biochemical data revealed substantial metabolic remodelling involving a shift to triacylglycerol utilization with adaptation to the consequent ketoacidosis by upregulation of cytochrome P450s. Paradoxically, the ketosis-driven P450 upregulation generated substantial levels of reactive oxygen species (ROS) yet conferred hypersensitivity to killing by hydrogen peroxide-induced inactivation of the P450s that reduced ROS levels. This emergent property of starvation-induced mycobacterial persistence represents a potentially exploitable vulnerability.

ORGANISM(S): Mycobacterium tuberculosis variant bovis BCG str. Pasteur 1173P2

PROVIDER: GSE66883 | GEO | 2016/08/25

SECONDARY ACCESSION(S): PRJNA278166

REPOSITORIES: GEO

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Project description:One of the most common metabolic defects of cancer cells is the deficiency in arginine synthesis due to suppressed expression of argininosuccinate synthetase 1 (ASS1) which renders cancer cells auxotrophic to external arginine supply. Arginine deprivation has been effectively used as a treatment for leukemias, with several clinical trials on solid tumors underway. We previously showed that in prostate cancer arginine depletion induced mitochondrial dysfunction and excessive ROS production resulting in chromatin autophagy, nuclear DNA leakage, and cellular death, but the detailed mechanism of arginine starvation-induced cell death remains unclear. In this study, we demonstrated that arginine deprivation coordinately suppressed metabolic genes, including those responsible for mitochondrial oxidative phosphorylation (OXPHOS), nucleotide metabolism, and DNA repair. The consequent ROS production and impaired DNA damage response resulted in nuclear DNA leakage and cGAS-STING activation which is accompanied by upregulation of type I interferon response. We also showed that coordinated silencing of OXPHOS and DNA repair genes is caused in part by the depletion of α-ketoglutarate (αKG) and inactivation of histone demethylases. Supplementing cell-permeable dimethyl α-ketoglutarate (DMKG) both reduced repressive histone methylations and partially restored OXPHOS gene expressions, mitochondrial functions, and mitigated nuclear DNA leakage. Using our dietary arginine-restriction model, we demonstrate that arginine starvation slows prostate cancer growth with evidence of enhanced interferon responses and recruitment of immune cells. Our data suggests arginine starvation induces cell killing of ASS1-low cancer cells by metabolic depletion and epigenetic silencing of metabolic genes, leading to DNA damage and leakage. Resulting cGAS-STING activation may further enhance these killing effects. We used microarray to analyze the expression difference between control and arginine-depleted cells to find out what genes involved in the regulation of mitochondrial function and arginine deprivation-induced cell death.

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Ketogenesis: An Achilles' heel of starvation-selected persistent mycobacteria

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