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The DEAD-box RNA helicase CshA is required for fatty acid homeostasis in Staphylococcus aureus

ABSTRACT: Staphylococcus aureus is an opportunistic pathogen that can grow in wide array of conditions: on abiotic surfaces, on the skin, in the nose, in planktonic or biofilms forms and can cause many type of infections. Consequently, S. aureus must be able to adapt rapidly to these changing growth conditions, an ability largely driven at the posttranscriptional level. RNA helicases of the DEAD-box family play an important part in this process. In particular, CshA, which is part of the degradosome, is required for the rapid turnover of certain mRNAs and its deletion results in cold-sensitivity. To understand the molecular basis of this phenotype, we conducted a large genetic screen isolating 82 independent suppressors of cold growth. Full genome sequencing revealed the fatty acid synthesis pathway affected in many suppressor strains. Consistent with that result, sublethal doses of triclosan, a FASII inhibitor, can partially restore growth of a cshA mutant in the cold. Overexpression of the genes involved in branch-chained fatty acid synthesis was also able to suppress the cold-sensitivity. Using gas chromatography analysis of fatty acids, we observed an imbalance of straight and branch-chained fatty acids in the cshA mutant, compared to the wild-type. This imbalance is compensated in the suppressor strains. Thus, we reveal for the first time that the cold sensitive growth phenotype of a DEAD-box mutant can be explained, at least partially, by an improper membrane composition. The defect correlates with an accumulation of the pyruvate dehydrogenase complex mRNA, which is inefficiently degraded in absence of CshA. We propose that the resulting accumulation of acetyl- CoA fuels straight-chained fatty acid production at the expense of the branched ones. Strikingly, addition of acetate into the medium mimics the cshA deletion phenotype, resulting in cold sensitivity suppressed by the mutations found in our genetic screen or by sublethal doses of triclosan.

ORGANISM(S): Staphylococcus aureus

PROVIDER: GSE133013 | GEO | 2020/04/21

REPOSITORIES: GEO

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Project description:Long-term consumption of fatty foods is associated with obesity, macrophage activation and inflammation, metabolic imbalance, and a reduced lifespan. We took advantage of Drosophila genetics to investigate the role of macrophages and the pathway(s) that govern their response to dietary stress. Flies fed a lipid-rich diet presented with increased fat storage, systemic JAK-STAT activation, reduced insulin sensitivity and hyperglycaemia, and a shorter lifespan. Drosophila macrophages scavenged lipids and produced the type 1 cytokine upd3, in a scavenger-receptor (croquemort) and JNK-dependent manner. Genetic depletion of macrophages, or macrophage-specific silencing of upd3 decreased JAK-STAT activation and rescued insulin sensitivity and the lifespan of Drosophila, but did not decrease fat storage. NF-M-NM-:B signalling made no contribution to the phenotype observed. These results identify an evolutionarily conserved M-bM-^@M-^Xscavenger receptor-JNK-Type 1 cytokineM-bM-^@M-^Y cassette in macrophages, which controls glucose metabolism and reduces lifespan in Drosophila maintained on a lipid-rich diet via activation of the JAK-STAT pathway Long-term consumption of fatty foods is associated with obesity, macrophage activation and inflammation, metabolic imbalance, and a reduced lifespan. We took advantage of Drosophila genetics to investigate the role of macrophages and the pathway(s) that govern their response to dietary stress. Flies fed a lipid-rich diet presented with increased fat storage, systemic JAK-STAT activation, reduced insulin sensitivity and hyperglycaemia, and a shorter lifespan. Drosophila macrophages scavenged lipids and produced the type 1 cytokine upd3, in a scavenger-receptor (croquemort) and JNK-dependent manner. Genetic depletion of macrophages, or macrophage-specific silencing of upd3 decreased JAK-STAT activation and rescued insulin sensitivity and the lifespan of Drosophila, but did not decrease fat storage. NF-M-NM-:B signalling made no contribution to the phenotype observed. These results identify an evolutionarily conserved M-bM-^@M-^Xscavenger receptor-JNK-Type 1 cytokineM-bM-^@M-^Y cassette in macrophages, which controls glucose metabolism and reduces lifespan in Drosophila maintained on a lipid-rich diet via activation of the JAK-STAT pathway 5 biological samples were FACS-sorted from different batches of Drosophila melanogaster males after 30 days on 15% lipid enriched diet (n=5) and control diet (n=5)

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The DEAD-box RNA helicase CshA is required for fatty acid homeostasis in Staphylococcus aureus

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