Mycobacterium tuberculosis Thioredoxin Reductase Is Essential for Thiol Redox Homeostasis but Plays a Minor Role in Antioxidant Defense

Abstract

Mycobacterium tuberculosis (Mtb) must cope with exogenous oxidative stress imposed by the host. Unlike other antioxidant enzymes, Mtb’s thioredoxin reductase TrxB2 has been predicted to be essential not only to fight host defenses but also for in vitro growth. However, the specific physiological role of TrxB2 and its importance for Mtb pathogenesis remain undefined. Here we show that genetic inactivation of thioredoxin reductase perturbed several growth-essential processes, including sulfur and DNA metabolism and rapidly killed and lysed Mtb. Death was due to cidal thiol-specific oxidizing stress and prevented by a disulfide reductant. In contrast, thioredoxin reductase deficiency did not significantly increase susceptibility to oxidative and nitrosative stress. In vivo targeting TrxB2 eradicated Mtb during both acute and chronic phases of mouse infection. Deliberately leaky knockdown mutants identified the specificity of TrxB2 inhibitors and showed that partial inactivation of TrxB2 increased Mtb’s susceptibility to rifampicin. These studies reveal TrxB2 as essential thiol-reducing enzyme in Mtb in vitro and during infection, establish the value of targeting TrxB2, and provide tools to accelerate the development of TrxB2 inhibitors.

Depleting Mycobacterium tuberculosis of the transcription termination factor Rho causes pervasive transcription and rapid death

“…This dependency on Rho is remarkable for two reasons, the first being that inactivation of Rho reduced CFU by five orders of magnitude within a week. For comparison, genetic inactivation of many other attractive targets for drug development only decreased CFU by three orders of magnitude or less over a similar time period34454647484950. Second, not all genes required for growth are required for non-replicating persistence and drugs, for example INH, which is cidal for growing bacteria, can be virtually inactive against non-replicating bacteria.…”

Mycobacterium tuberculosis Proteome Response to Antituberculosis Compounds Reveals Metabolic “Escape” Pathways That Prolong Bacterial Survival

“…Thioredoxin (Trx) genes are highly expressed during M. tuberculosis infection and contribute to natural resistance to oxidative killing that the pathogen encounters in the phagosomal environment. In vivo studies have demonstrated that, by targeting thioredoxin reductase TrxB2, M. tuberculosis can be cleared during acute and chronic mouse infections (26). Interestingly, it was also found that the partial inactivation of TrxB2 increases M. tuberculosis susceptibility to rifampin and synergizes bacterial killing with this frontline antituberculosis drug (26).…”

Deletion of glutaredoxin promotes oxidative tolerance and intracellular infection in Listeria monocytogenes

“…Moreover, under oxidative stress, glutaredoxin may catalyze formation of mixed disulfides from GSSG, which may be of a protective function to avoid oxidation of a thiol to higher oxidation state [25]. Unlike with the fact that the bacterial thioredoxins have been widely shown to play major roles in protection of cells against toxic oxygen species as well as maintaining the intracellular thio-disulfide balance [8,26], limited data had been available on the role of the glutaredoxins. However, glutaredoxins from E. coli has previously been demonstrated to contribute to the defense against oxidative stress.…”