Biology subjects

Troll, M.

Publications and source records attributed to Troll, M..

6 recordsLinked to original sources

bioRxiv2025

Structural and functional analysis of the Mycobacterium tuberculosis MmpS5L5 efflux pump presages a pathway to increased bedaquiline resistance

Bedaquiline, an antitubercular drug that targets ATP-synthase, is a key component of a new oral drug regimen that has revolutionized the treatment of multi drug resistant tuberculosis. Clinical bedaquiline resistance in Mycobacterium tuberculosis has rapidly emerged, primarily due to mutations in the transcriptional repressor, Rv0678 that result in upregulation of the Resistance-Nodulation-Division (RND) efflux pump MmpS5/MmpL5 (MmpS5L5). Here, to understand how MmpS5L5 effluxes bedaquiline, we determined the structure of the MmpS5L5 complex using cryo-electron microscopy, revealing a novel trimeric architecture distinct from the canonical tripartite RND efflux pumps of Gram-negative bacteria. Structure prediction modelling in conjunction with functional genetic analysis indicates that it uses a periplasmic coiled-coil tube to transport molecules across the cell wall. Structure-guided genetic approaches identify MmpL5 mutations that alter bedaquiline transport; these mutations converge on a region in MmpL5 located in the lower portion of the periplasmic cavity, proximal to the outer leaflet of the inner membrane, suggesting a route for bedaquiline entry into the pump. While currently known clinical resistance to bedaquiline is due to pump upregulation, our findings that several MmpL5 variants increase bedaquiline efflux may presage the emergence of additional modes of clinical resistance. Significance StatementResistance to bedaquiline, a cornerstone drug for treating multidrug-resistant tuberculosis, is rapidly emerging due to mutations that upregulate expression of the MmpS5L5 efflux pump. Here, we reveal the cryo-EM structure of this pump, showing a novel trimeric architecture and a unique -helical coiled-coil tube for drug transport. Structure-guided genetic analysis identifies MmpL5 variants that further increase bedaquiline efflux, suggesting potential resistance mechanisms beyond pump upregulation.

microbiology↗

bioRxiv2025

Verapamil and its metabolite norverapamil inhibit the Mycobacterium tuberculosis MmpS5L5 efflux pump to potentiate the activity bedaquiline and other antitubercular drugs

Bedaquiline is the cornerstone of a new regimen for the treatment of drug-resistant tuberculosis. However, its clinical use is threatened by the emergence of bedaquiline-resistant strains of Mycobacterium tuberculosis. Bedaquiline targets mycobacterial ATP synthase but the predominant route to clinical bedaquiline resistance is via upregulation of the MmpS5L5 efflux pump due to mutations that inactivate the transcriptional repressor Rv0678. Here, we show that the MmpS5L5 efflux pump reduces susceptibility to bedaquiline as well as its new, more potent derivative TBAJ-876 and other antimicrobial substrates, including clofazimine and the DprE1 inhibitors PBTZ-169 and OPC-167832. Furthermore, the increased resistance of Rv0678 mutants stems entirely from increased MmpS5L5 activity. These results highlight the potential of a pharmacological MmpS5L5 inhibitor to increase drug efficacy. Verapamil, primarily used as a calcium channel inhibitor, is known to inhibit diverse efflux pumps and to potentiate bedaquiline and clofazimine activity in M. tuberculosis. Here, we show that verapamil potentiates the activity of multiple diverse MmpS5L5 substrates. Using biochemical approaches, we demonstrate that verapamil does not exert this effect by acting as a disruptor of the protonmotive force used to power MmpS5L5, as previously proposed, suggesting that verapamil inhibits the function of the MmpS5L5 pump. Finally, norverapamil, the major verapamil metabolite, which has greatly reduced calcium channel activity, has equal potency in reducing resistance to MmpS5L5 substrates. Our findings highlight verapamils potential for enhancing bedaquiline TB treatment, for preventing acquired resistance to bedaquiline and other MmpS5L5 substrates, while also providing the impetus to identify additional MmpS5L5 inhibitors. Significance StatementBedaquiline, an antitubercular drug targeting ATP synthase, forms the backbone of highly efficacious treatment regimens for drug-resistant tuberculosis. Bedaquiline resistance is emerging as a significant problem and is most commonly caused by mutations in Rv0678 that result in upregulation of the MmpS5L5 efflux pump. Here we define the contribution of the MmpS5L5 efflux pump to drug resistance in wild-type and Rv0678 mutant strains and show that the commonly used drug verapamil can inhibit MmpS5L5 activity. This suggests that this safe and inexpensive drug may be useful in enhancing bedaquiline treatment of TB and to help prevent bedaquiline acquired resistance.

microbiology↗

bioRxiv2022

Gaucher Disease Protects Against Tuberculosis

Biallelic mutations in the glucocerebrosidase (GBA1) gene cause Gaucher disease, characterized by lysosomal accumulation of glucosylceramide and glucosylsphingosine in macrophages. This and other lysosomal diseases occur with high frequency in Ashkenazi Jews. It has been proposed that the underlying mutations confer a selective advantage, in particular conferring protection against tuberculosis. Here, using a zebrafish Gaucher disease model, we find that the mutation GBA1 N370S, predominant among Ashkenazi Jews, increases resistance to tuberculosis through the microbicidal activity of glucosylsphingosine in macrophage lysosomes. Consistent with lysosomal accumulation occurring only in homozygotes, heterozygotes remain susceptible to tuberculosis. Thus, our findings reveal a mechanistic basis for protection against tuberculosis by GBA1 N370S and provide biological plausibility for its selection if the relatively mild deleterious effects in homozygotes were offset by significant protection against tuberculosis, a rampant killer of the young in Europe through the Middle Ages into the 19th century. Significance StatementGaucher disease is a recessively inherited disorder in which the lipids glucosylceramide and glucosylsphingosine accumulate in lysosomes of macrophages. Macrophages are the first immune cells to engulf infecting bacteria and we find that glucosylsphingosine increases their ability to kill Mycobacterium tuberculosis that causes tuberculosis. Gaucher disease due to a particular mutation is frequent in Ashkenazi Jews. Since from the middle ages they were often confined to areas of high tuberculosis prevalence, it has been proposed that the mutation prevailed because heterozygotes, who do not accumulate lipids nor manifest Gaucher disease, were protected. Our findings raise the possibility that selection operated on homozygotes manifesting mild forms of Gaucher disease who were protected against tuberculosis which would often have been fatal.

microbiology↗

bioRxiv2020

Elevated cerebrospinal fluid cytokine levels in tuberculous meningitis predict survival in response to dexamethasone

Adjunctive treatment with anti-inflammatory corticosteroids like dexamethasone increases survival in tuberculosis meningitis. Dexamethasone responsiveness associates with a C/T variant in Leukotriene A4 Hydrolase (LTA4H), which regulates expression of the pro-inflammatory mediator leukotriene B4 (LTB4). TT homozygotes, with increased LTB4, have the highest survival when treated with dexamethasone and the lowest survival without. While the T allele is present in only a minority of the worlds population, corticosteroids confer modest survival benefit worldwide. Using Bayesian methods, we examined how pre-treatment levels of cerebrospinal fluid (CSF) pro-inflammatory cytokines affect survival in dexamethasone-treated tuberculous meningitis. LTA4H TT homozygosity was associated with global cytokine increases, including TNF. Association between higher cytokine levels and survival extended to non-TT patients, suggesting that other genetic variants may also induce dexamethasone-responsive pathological inflammation. These findings warrant studies that tailor dexamethasone therapy to pre-treatment CSF cytokine concentrations, while searching for additional genetic loci shaping the inflammatory milieu.

immunology↗

bioRxiv2020

A Bayesian analysis of the association between Leukotriene A4 Hydrolase genotype and survival probability of tuberculous meningitis patients treated with adjunctive dexamethasone

Tuberculous meningitis (TBM) remains the most devastating form of tuberculosis (TB) with high mortality despite effective antimicrobial treatment. As mortality has been linked to excessive inflammation, anti-inflammatory glucocorticoids are now routinely used as adjunctive treatment with antimicrobial therapy. However, they reduce mortality by only ~ 30%, raising the possibility that only a subset of TBM deaths are caused by inflammatory pathophysiology. Studies in Vietnam found that the survival benefit of adjunctive glucocorticoids was limited to individuals with a common promoter variant in the leukotriene A4 hydrolase (LTA4H) gene encoding an enzyme that regulates inflammatory eicosanoid expression. The variant constitutes a C/T transition with TT homozygotes having increased expression over CT heterozygotes and CC homozygotes. In Vietnam, the LTA4H TT genotype predicted survival, consistent with dexamethasone benefiting only those individuals with a dysregulated hyper-inflammatory response. However, a study of TBM patients in Indonesia did not find the LTA4H TT genotype to confer a significant survival benefit. Given the potential of personalized life-saving anti-inflammatory therapies guided by LTA4H genotype, we have used Bayesian methods to analyze the data from both studies. Bayesian analysis reveals that the LTA4H TT genotype confers survival benefit in both the Vietnam and Indonesia cohorts that begins within days and continues long-term. However, its benefit is nullified in the most severe cases where other factors cause early mortality. LTA4H TT genotype is associated with increased survival in HIV-positive patients also. Thus, our analysis extends the association of LTA4H genotype with TBM survival to populations outside of Vietnam and to HIV-positive patients. Patient LTA4H genotyping used in conjunction with disease severity assessment may help to target glucocorticoids to patients most likely to benefit from this broadly-acting immunosuppressive regimen despite its significant adverse effects.

molecular biology↗

bioRxiv2019

Arrhythmic gut microbiome signatures for risk profiling of Type-2 Diabetes

To combat the epidemic increase in Type-2-Diabetes (T2D), risk factors need to be identified. Diet, lifestyle and the gut microbiome are among the most important factors affecting metabolic health. We demonstrate in 1,976 subjects of a prospective population cohort that specific gut microbiota members show diurnal oscillations in their relative abundance and we identified 13 taxa with disrupted rhythmicity in T2D. Prediction models based on this signature classified T2D with an area under the curve of 73%. BMI as microbiota-independent risk marker further improved diagnostic classification of T2D. The validity of this arrhythmic risk signature to predict T2D was confirmed in 699 KORA subjects five years after initial sampling. Shotgun metagenomic analysis linked 26 pathways associated with xenobiotic, amino acid, fatty acid, and taurine metabolism to the diurnal oscillation of gut bacteria. In summary, we determined a cohort-specific risk pattern of arrhythmic taxa which significantly contributes to the classification and prediction of T2D, highlighting the importance of circadian rhythmicity of the microbiome in targeting metabolic human diseases.

microbiology↗