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A Conserved Mitochondrial Surveillance Pathway Is Required for Defense against Pseudomonas aeruginosa

ABSTRACT: In the arms race of bacterial pathogenesis, bacteria produce an array of toxins and virulence factors that disrupt host processes while hosts respond with immune countermeasures. One key virulence mediator of the ubiquitous, opportunistic, extracellular pathogen Pseudomonas aeruginosa is the iron-binding siderophore pyoverdin (PMID:10722571;PMID: 8550201). The mechanisms used by pyoverdin to acquire iron from the host remain incompletely elucidated. Here we demonstrate that mitochondria represent an important target for iron acquisition and that exposure to this toxin results in loss of mitochondrial membrane potential, altered mitochondrial dynamics, and mitophagy in both Caenorhabditis elegans and mammalian cells. We also show that animal mitophagy protects the consequences of siderophore activity, conferring resistance to pyoverdin-mediated host killing. In C. elegans, the conserved autophagic genes bec-1/BECN1 and lgg-1/LC3, and the mitophagic regulator pink-1/PINK1 are required for iron chelator-elicited mitochondrial turnover and provide protection against iron sequestration by P. aeruginosa, likely by ameliorating the mitochondrial damage. While autophagic mechanisms have been implicated in the destruction of intracellular bacteria via a process called “xenophagy” (PMID: 24005326), our findings represent the first report of resistance to an extracellular pathogen being conferred by authentic autophagic activity that targets host organelles.

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE55422 | GEO | 2017/06/20

SECONDARY ACCESSION(S): PRJNA239551

REPOSITORIES: GEO

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Project description:Iron is an essential cofactor for a wide range of cellular processes. Previous studies have shown that siderophore-mediated uptake and intracellular handling of iron are crucial for virulence of Aspergillus fumigatus. Here we show that the bzip-type transcription factor HapX plays a crucial role in the transcriptional remodeling required for adaption to iron starvation in this opportunistic fungal pathogen. HapX was found to be interconnected in a negative feed-back loop with the previously identified iron regulator SreA: SreA repressed expression of hapX during iron sufficiency and HapX repressed sreA during iron starvation. Genome-wide transcriptional profiling and analysis of selected metabolites (protophorphyrine IX, siderophores and amino acids) indicated extensive metabolic remodeling in response to iron starvation. HapX was found to participate in both, repression and activation of genes during iron starvation. HapX was in particular required for repression of iron-dependent and mitochondrial-localized activities including respiration, TCA cycle, amino acid metabolism, iron-sulfur-cluster biosynthesis and heme biosynthesis. Pathways positively affected by HapX included production of siderophores and the ribotoxin and major allergen AspF1. Analysis of the free amino acid pool revealed HapX-dependent coordination of the production of siderophores with the supply of its precursor ornithine. Consistent with the hapX expression pattern, HapX-deficiency was deleterious with respect to growth rate and conidiation during iron depleted but not iron-replete conditions. HapX-deficiency caused significant attenuation of virulence in a murine model aspergillosis underlining that A. fumigatus faces iron starvation in the host and that the HapX-dependent metabolic reprogramming is therefore crucial for virulence. A. fumigatus 293 and hapX mutants were grown in the presence and absence of iron and in cultures shifted from no iron to iron-containing conditions after 1 h incubation. Hybridizations were performed with biological replicates for wt vs hapX +/- iron. For the iron-shift experiments, there were biological replicates for wt in both conditions and for hapX in -iron but there was only a single biological sample for hapX iron-shift sample. All hybs were performed with flip-dye pairs.

Project description:Bacterial metabolites are substrates of virulence factors of uropathogenic Escherichia coli (UPEC), but the mechanism underlying the role of functional metabolites in bacterial virulence from the perspective of small molecular metabolism is unclear. In the present study, we used a strategy of functional metabolomics integrated with bacterial genetics in attempt to decipher the mechanism of virulence formation in Escherichia coli (E. coli) from the viewpoint of small molecule metabolism. We identified the virulence-associated metabolome via analysis of the primary metabolome of the pathogenic UTI89 strain and the non-pathogenic MG1655 strain. Then, the iron-mediated virulence associated metabolome was identified by an iron fishing strategy. Also, the mechanism of siderophores in regulating pathogenicity in different environments was explored by investigating the effect of iron on siderophore biosynthesis. Finally, by knocking out genes related to siderophore biosynthesis, siderophore transport and iron utilization, siderophores dependent iron-regulating virulence associated metabolome, including 18 functional metabolites, was identified and verified to be involved in the regulation of bacterial virulence. Based on this we found that these functional metabolites regulated the virulence of E. coli by targeting multiple metabolic pathways in an iron-siderophores dependent manner. Moreover, a quantitative proteomics approach was implemented to further elucidate the mechanism of functional metabolites and functional proteins in modulating bacterial virulence. And our findings demonstrated that functional proteins regulated the virulence of E. coli by mediating iron binding, iron-siderophore transmembrane transport, and the biosynthesis and expression of functional metabolites. Interestingly, we found that functional metabolites enhance the virulence of E. coli by specifically modulating the key metabolic pathways involved in purine metabolism, proline metabolism, arginine metabolism and pyrimidine metabolism. Taken together, our study identified for the first time 18 functional metabolites regulating the of E. coli virulence, greatly enriching our understanding of the mechanism of functional metabolites that regulate the E. coli virulence by targeting primary metabolism, which will largely contribute to the development of new strategies to target virulence-based diagnosis and therapy of infections caused by different pathogens.

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A Conserved Mitochondrial Surveillance Pathway Is Required for Defense against Pseudomonas aeruginosa

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