Adaptation to Environmental Stimuli within the Host: Two-Component Signal Transduction Systems of Mycobacterium tuberculosis

Bretl, Daniel J.; Demetriadou, Chrystalla; Zahrt, Thomas C.

doi:10.1128/mmbr.05004-11

Cited by 122 publications

(124 citation statements)

References 185 publications

(319 reference statements)

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“…The coding sequence for MS_2695 in M. smegmatis mc 2 155 was deleted using a standard two-step homologous recombination procedure, as described previously (15). Briefly, pTZ1231 was electroporated into wild-type M. smegmatis mc 2 155, and hygromycin-resistant (Hyg r ) transformations selected.…”

Section: Methodsmentioning

confidence: 99%

Rv2744c Is a PspA Ortholog That Regulates Lipid Droplet Homeostasis and Nonreplicating Persistence in Mycobacterium tuberculosis

et al. 2016

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Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), remains a significant cause of morbidity and mortality worldwide, despite the availability of a live attenuated vaccine and anti-TB antibiotics. The vast majority of individuals infected with M. tuberculosis develop an asymptomatic latent infection in which the bacterium survives within host-generated granulomatous lesions in a physiologically altered metabolic state of nonreplicating persistence. The granuloma represents an adverse environment, as M. tuberculosis is exposed to various stressors capable of disrupting the essential constituents of the bacterium. In Gram-negative and Gram-positive bacteria, resistance to cell envelope stressors that perturb the plasma membrane is mediated in part by proteins comprising the phage shock protein (Psp) system. PspA is an important component of the Psp system; in the presence of envelope stress, PspA localizes to the inner face of the plasma membrane, homo-oligomerizes to form a large scaffold-like complex, and helps maintain plasma membrane integrity to prevent a loss of proton motive force. M. tuberculosis and other members of the Mycobacterium genus are thought to encode a minimal functional unit of the Psp system, including an ortholog of PspA. Here, we show that Rv2744c possesses structural and physical characteristics that are consistent with its designation as a PspA family member. However, although Rv2744c is upregulated under conditions of cell envelope stress, loss of Mycobacterium tuberculosis is the causative agent of the respiratory disease tuberculosis (TB) and is a human-specific pathogen of global importance. This bacterium is responsible for Ͼ9.6 million new cases of TB and 1.5 million deaths annually (1), ranking TB as the leading cause of death in the world due to an infectious agent, alongside HIV/AIDS. A key aspect of the M. tuberculosis life cycle is its ability to establish asymptomatic latent infections and reactivate to cause active disease and transmission to new hosts (reviewed in reference 2). During latency, M. tuberculosis exists in a state of nonreplicating persistence (NRP), a poorly understood physiological state in which the bacterium can utilize alternative carbon sources and energy-generating pathways for long-term survival within the host (3-6). While a live attenuated vaccine for TB is available (Mycobacterium bovis bacillus Calmette-Guérin [BCG]), its efficacy at preventing adult pulmonary TB and thus M. tuberculosis retransmission is highly varied (7,8). Furthermore, M. tuberculosis exhibits increased phenotypic resistance to anti-TB antibiotics during NRP (2, 9), making it more difficult to kill this organism in latently infected individuals. Therefore, new strategies and/or therapeutics are urgently needed to help eradicate TB. This will require an improved understanding of the mechanisms utilized by M. tuberculosis to persist and/or reactivate within the host.

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Section: Methodsmentioning

confidence: 99%

Rv2744c Is a PspA Ortholog That Regulates Lipid Droplet Homeostasis and Nonreplicating Persistence in Mycobacterium tuberculosis

et al. 2016

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“…Phosphorylation of the RR leads to activation of its DNA binding function and transcriptional regulation of a distinct set of genes. The M. tuberculosis genome encodes 11 paired TCSs and several orphan SKs and RRs (Bretl et al, 2011). We have established a link between poly P metabolism, the TCS encoded by mprAB, the extracytoplasmic function sigma factor SigE and the stringent response regulator rel in M. tuberculosis (Sureka et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Polyphosphate kinase 1, a central node in the stress response network of Mycobacterium tuberculosis, connects the two-component systems MprAB and SenX3–RegX3 and the extracytoplasmic function sigma factor, sigma E

Sanyal

Banerjee

et al. 2013

Microbiology

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Polyphosphate (poly P) metabolism regulates the stress response in mycobacteria. Here we describe the regulatory architecture of a signal transduction system involving the two-component system (TCS) SenX3-RegX3, the extracytoplasmic function sigma factor sigma E (SigE) and the poly P-synthesizing enzyme polyphosphate kinase 1 (PPK1). The ppk1 promoter of Mycobacterium tuberculosis is activated under phosphate starvation. This is attenuated upon deletion of an imperfect palindrome likely representing a binding site for the response regulator RegX3, a component of the two-component system SenX3-RegX3 that responds to phosphate starvation. Binding of phosphorylated RegX3 to this site was confirmed by electrophoretic mobility shift assay. The activity of the ppk1 promoter was abrogated upon deletion of a putative SigE binding site. Pull-down of SigE from M. tuberculosis lysates of phosphate-starved cells with a biotinylated DNA harbouring the SigE binding site confirmed the likely binding of SigE to the ppk1 promoter. In vitro transcription corroborated the involvement of SigE in ppk1 transcription. Finally, the overexpression of RseA (anti-SigE) attenuated ppk1 expression under phosphate starvation, supporting the role of SigE in ppk1 transcription. The regulatory elements identified in ppk1 transcription in this study, combined with our earlier observation that PPK1 is itself capable of regulating sigE expression via the MprAB TCS, suggest the presence of multiple positivefeedback loops in this signalling circuit. In combination with the sequestering effect of RseA, we hypothesize that this architecture could be linked to bistability in the system that, in turn, could be a key element of persistence in M. tuberculosis.

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“…Characterization of such genes presents a daunting task. M. tuberculosis is thought to be subjected to a myriad of conditions during its life cycle in the host, such as low pH, reactive oxygen and nitrogen species, and so on (6,7). Understanding how M. tuberculosis adapts to and even thrives in such diverse environments is critical to our understanding of the pathology itself and for the discovery of novel therapeutics to treat tuberculosis.…”

mentioning

confidence: 99%

Discovery of a glycerol 3-phosphate phosphatase reveals glycerophospholipid polar head recycling in Mycobacterium tuberculosis

Larrouy-Maumus

Biswas

Hunt

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Functional assignment of enzymes encoded by the Mycobacterium tuberculosis genome is largely incomplete despite recent advances in genomics and bioinformatics. Here, we applied an activitybased metabolomic profiling method to assign function to a unique phosphatase, Rv1692. In contrast to its annotation as a nucleotide phosphatase, metabolomic profiling and kinetic characterization indicate that Rv1692 is a D,L-glycerol 3-phosphate phosphatase. Crystal structures of Rv1692 reveal a unique architecture, a fusion of a predicted haloacid dehalogenase fold with a previously unidentified GCN5-related N-acetyltransferase region.Although not directly involved in acetyl transfer, or regulation of enzymatic activity in vitro, this GCN5-related N-acetyltransferase region is critical for the solubility of the phosphatase. Structural and biochemical analysis shows that the active site features are adapted for recognition of small polyol phosphates, and not nucleotide substrates. Functional assignment and metabolomic studies of M. tuberculosis lacking rv1692 demonstrate that Rv1692 is the final enzyme involved in glycerophospholipid recycling/catabolism, a pathway not previously described in M. tuberculosis.haloacid dehalogenase superfamily | enzyme function | pathway discovery E ach year, 1.4 million people succumb to tuberculosis, making Mycobacterium tuberculosis the deadliest bacterium affecting mankind (1). In addition, the dissemination of strains resistant to several antibiotics underscores the need for better understanding of this pathogen and for the development of novel vaccines and therapeutics (2, 3). Our approach to elucidating the unique pervasiveness of M. tuberculosis is through comprehensive discovery and characterization of metabolic pathways, as metabolism underlies survival of the bacteria both inside and outside the host and can contribute to phenotypic and genetic drug resistance.The M. tuberculosis genome encodes for 4,043 genes, of which 3,933 encode proteins (4, 5). Many genes with essential functions, such as DNA replication, protein and RNA synthesis, and cell-division, have close homologs in other bacteria, and their functions are annotated largely on the basis of analysis of their counterparts. However, functions of at least one-third of the genes are unknown or putative (4). In particular, little is known about genes that are not conserved or conditionally important. Characterization of such genes presents a daunting task. M. tuberculosis is thought to be subjected to a myriad of conditions during its life cycle in the host, such as low pH, reactive oxygen and nitrogen species, and so on (6, 7). Understanding how M. tuberculosis adapts to and even thrives in such diverse environments is critical to our understanding of the pathology itself and for the discovery of novel therapeutics to treat tuberculosis.We applied an innovative, activity-based metabolomic profiling (ABMP) approach to assign function to orphan (without a priori known substrates/products) mycobacterial enzymes and to discover unk...

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Adaptation to Environmental Stimuli within the Host: Two-Component Signal Transduction Systems of Mycobacterium tuberculosis

Cited by 122 publications

References 185 publications

Rv2744c Is a PspA Ortholog That Regulates Lipid Droplet Homeostasis and Nonreplicating Persistence in Mycobacterium tuberculosis

Rv2744c Is a PspA Ortholog That Regulates Lipid Droplet Homeostasis and Nonreplicating Persistence in Mycobacterium tuberculosis

Polyphosphate kinase 1, a central node in the stress response network of Mycobacterium tuberculosis, connects the two-component systems MprAB and SenX3–RegX3 and the extracytoplasmic function sigma factor, sigma E

Discovery of a glycerol 3-phosphate phosphatase reveals glycerophospholipid polar head recycling in Mycobacterium tuberculosis

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