5′‐Adenosinephosphosulphate reductase (CysH) protects <i>Mycobacterium tuberculosis</i> against free radicals during chronic infection phase in mice

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Multidrug resistance, strong side effects, and compliance problems in TB chemotherapy mandate new ways to kill Mycobacterium tuberculosis (Mtb). Here we show that deletion of the gene encoding homoserine transacetylase (metA) inactivates methionine and S-adenosylmethionine (SAM) biosynthesis in Mtb and renders this pathogen exquisitely sensitive to killing in immunocompetent or immunocompromised mice, leading to rapid clearance from host tissues. Mtb ΔmetA is unable to proliferate in primary human macrophages, and in vitro starvation leads to extraordinarily rapid killing with no appearance of suppressor mutants. Cell death of Mtb ΔmetA is faster than that of other auxotrophic mutants (i.e., tryptophan, pantothenate, leucine, biotin), suggesting a particularly potent mechanism of killing. Time-course metabolomics showed complete depletion of intracellular methionine and SAM. SAM depletion was consistent with a significant decrease in methylation at the DNA level (measured by single-molecule real-time sequencing) and with the induction of several essential methyltransferases involved in biotin and menaquinone biosynthesis, both of which are vital biological processes and validated targets of antimycobacterial drugs. Mtb ΔmetA could be partially rescued by biotin supplementation, confirming a multitarget cell death mechanism. The work presented here uncovers a previously unidentified vulnerability of Mtb-the incapacity to scavenge intermediates of SAM and methionine biosynthesis from the host. This vulnerability unveils an entirely new drug target space with the promise of rapid killing of the tubercle bacillus by a new mechanism of action.host-pathogen interaction | bactericidal auxotrophy | amino acid biosynthesis | metabolism U nderstanding the metabolic interactions between an invading microbe and its host is becoming a new cornerstone of host-pathogen research (1-3). Many intracellular pathogens modulate the host response to satisfy their nutritional needs and as a result have become auxotrophic for several essential amino acids and cofactors (4-6). Mycobacterium tuberculosis (Mtb), arguably the most deadly bacterial pathogen in the world (7), adopted a different strategy. This ultra-slow-growing bacterium is prototrophic for all essential cofactors and amino acids, suggesting that it either dwells in host compartments where such metabolites are unavailable or actively chooses this autarkic lifestyle to retain metabolic flexibility and remain invisible to the host. Indeed, much of Mtb's long-term success as a human pathogen is ascribed to its extraordinary stealth in the face of host immunity (8, 9); Mtb's ability to evade detection by the host might explain why devising an efficient vaccine has failed thus far and why drug therapy is difficult. Therefore, understanding Mtb's in vivo metabolic requirements could help in the development of much-needed new strategies for antimycobacterial therapy.Methionine and S-adenosylmethionine (SAM) are essential metabolites that have gained considerable scientific attenti...

Section: Discussioncontrasting

confidence: 53%

Essential roles of methionine and S -adenosylmethionine in the autarkic lifestyle of Mycobacterium tuberculosis

Berney

Berney-Meyer

Wong

et al. 2015

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163

“…To test for potential attenuation of the WT strain, two additional mutants were generated and analyzed in parallel experiments by using identical methods. One of these mutants, a deletion of a nonessential gene, behaved as WT, and the other, a sulfur auxotroph (⌬cysH) (29,36), was attenuated relative to WT (Fig. 4A).…”

Section: Resultsmentioning

confidence: 99%

A sulfated metabolite produced bystf3negatively regulates the virulence ofMycobacteriumtuberculosis

Mougous

Senaratne

Kim

et al. 2006

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Sulfated molecules have been shown to modulate isotypic interactions between cells of metazoans and heterotypic interactions between bacterial pathogens or symbionts and their eukaryotic host cells. Mycobacterium tuberculosis, the causative agent of tuberculosis, produces sulfated molecules that have eluded functional characterization for decades. We demonstrate here that a previously uncharacterized sulfated molecule, termed S881, is localized to the outer envelope of M. tuberculosis and negatively regulates the virulence of the organism in two mouse infection models. Furthermore, we show that the biosynthesis of S881 relies on the universal sulfate donor 3 -phosphoadenosine-5 -phosphosulfate and a previously uncharacterized sulfotransferase, stf3. These findings extend the known functions of sulfated molecules as general modulators of cell-cell interactions to include those between a bacterium and a human host.Fourier transform ion cyclotron resonance ͉ hypervirulent ͉ sulfate assimilation ͉ kinase ͉ adenosine-5-phosphosulfate A wide variety of organisms use sulfated molecules to control extracellular events. In mammals, sulfation of tyrosine residues on cell surface proteins is important for the interactions of chemokines with certain chemokine receptors, and for viral binding and entry (1-6). Sulfated glycans modulate processes such as leukocyte homing to lymph nodes, clearance of serum glycoproteins, and blood coagulation (7-9). Members of the glypican family that are modified with sulfated glycosaminoglycans guide organ development in Drosophila by maintaining a morphogen concentration gradient (10).In bacteria, sulfated glycolipids have been shown to serve as extracellular signaling molecules (11). The nitrogen fixing bacterium Sinorhizobium meliloti secretes the nodulation factor NodRm-1, a tetrasaccharide bearing both sulfate and lipid modifications (12). This molecule binds a receptor on the host plant, normally alfalfa, and induces root nodule formation. The sulfate group is critical for the function of NodRm-1, because the unsulfated form fails to induce root nodulation in alfalfa. In the rice blight-causing pathogen Xanthomonas oryzae, several genes involved in the synthesis of sulfated metabolites have been identified as avirulence factors with respect to certain host strains (13,14). These examples suggest that bacterial sulfated metabolites can participate in dialogue with eukaryotic hosts, analogous to their role in mammalian cell-cell communication.Mycobacteria produce an unusually complex array of sulfated structures (11). Sulfolipid-1 (SL-1), an abundant component of the cell envelope of M. tuberculosis, is the best characterized of these molecules. SL-1 has generated much interest because of its elaborate structure and the observation that its abundance correlates with strain virulence (15)(16)(17)(18)(19)(20)(21)(22). Advances in M. tuberculosis genetics and genome sequence data facilitated several contemporary studies that addressed aspects of the biosynthesis and the function of SL-1 in v...

“…M. tuberculosis also secretes superoxide dismutase encoded by sodA (24) which may protect against ROI, although conclusive data on this function are lacking in M. tuberculosis. Various cell wall components (25,26), reductases (27,28), and the genes responsible for mycothiol production (29) also appear to play a protective role. Lsr2 appears to use a different mechanism to protect mycobacteria against oxidative stress that requires direct protein-DNA binding.…”

Section: Discussionmentioning

confidence: 99%

The multifunctional histone-like protein Lsr2 protects mycobacteria against reactive oxygen intermediates

Colangeli

Haq

Arcus

et al. 2009

121

112

Mycobacterium tuberculosis has evolved a number of strategies to survive within the hostile environment of host phagocytes. Reactive nitrogen and oxygen intermediates (RNI and ROI) are among the most effective antimycobacterial molecules generated by the host during infection. Lsr2 is a M. tuberculosis protein with histonelike features, including the ability to regulate a variety of transcriptional responses in mycobacteria. Here we demonstrate that Lsr2 protects mycobacteria against ROI in vitro and during macrophage infection. Furthermore, using macrophages derived from NOS ؊/؊ and Phox ؊/؊ mice, we demonstrate that Lsr2 is important in protecting against ROI but not RNI. The protection provided by Lsr2 protein is not the result of its ability to either bind iron or scavenge hydroxyl radicals. Instead, electron microscopy and DNAbinding studies suggest that Lsr2 shields DNA from reactive intermediates by binding bacterial DNA and physically protecting it. Thus, Lsr2 appears to be a unique protein with both histone-like properties and protective features that may be central to M. tuberculosis pathogenesis. In addition, evidence indicates that lsr2 is an essential gene in M. tuberculosis. Because of its essentiality, Lsr2 may represent an excellent candidate as a drug target.Mycobacterium tuberculosis ͉ ROI ͉ DPS ͉ DNA