A Novel Small-Molecule Inhibitor of the Mycobacterium tuberculosis Demethylmenaquinone Methyltransferase MenG Is Bactericidal to Both Growing and Nutritionally Deprived Persister Cells (original) (raw)
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Enhanced respiration prevents drug tolerance and drug resistance in Mycobacterium tuberculosis
Proceedings of the National Academy of Sciences of the United States of America, 2017
Persistence, manifested as drug tolerance, represents a significant obstacle to global tuberculosis control. The bactericidal drugs isoniazid and rifampicin kill greater than 99% of exponentially growing Mycobacterium tuberculosis (Mtb) cells, but the remaining cells are persisters, cells with decreased metabolic rate, refractory to killing by these drugs, and able to generate drug-resistant mutants. We discovered that the combination of cysteine or other small thiols with either isoniazid or rifampicin prevents the formation of drug-tolerant and drug-resistant cells in Mtb cultures. This effect was concentration- and time-dependent, relying on increased oxygen consumption that triggered enhanced production of reactive oxygen species. In infected murine macrophages, the addition of N-acetylcysteine to isoniazid treatment potentiated the killing of Mtb Furthermore, we demonstrate that the addition of small thiols to Mtb drug treatment shifted the menaquinol/menaquinone balance toward...
Antimicrobial Agents and Chemotherapy, 2019
Mycobacterium tuberculosis is the leading cause of morbidity and death resulting from infectious disease worldwide. The incredible disease burden, combined with the long course of drug treatment and an increasing incidence of antimicrobial resistance among M. tuberculosis isolates, necessitates novel drugs and drug targets for treatment of this deadly pathogen. Recent work has produced several promising clinical candidates targeting components of the electron transport chain (ETC) of M. tuberculosis, highlighting this pathway's potential as a drug target. Menaquinone is an essential component of the M. tuberculosis ETC, as it functions to shuttle electrons through the ETC to produce the electrochemical gradient required for ATP production for the cell. We show that inhibitors of MenA, a component of the menaquinone biosynthetic pathway, are highly active against M. tuberculosis. MenA inhibitors are bactericidal against M. tuberculosis under both replicating and nonreplicating conditions, with 10-fold higher bactericidal activity against nutrientstarved bacteria than against replicating cultures. MenA inhibitors have enhanced activity in combination with bedaquiline, clofazimine, and inhibitors of QcrB, a component of the cytochrome bc 1 oxidase. Together, these data support MenA as a viable target for drug treatment against M. tuberculosis. MenA inhibitors not only kill M. tuberculosis in a variety of physiological states but also show enhanced activity in combination with ETC inhibitors in various stages of clinical trial testing.
Multitarget Drug Discovery for Tuberculosis and Other Infectious Diseases
Journal of Medicinal Chemistry, 2014
We report the discovery of a series of new drug leads that have potent activity against Mycobacterium tuberculosis as well as against other bacteria, fungi, and a malaria parasite. The compounds are analogues of the new tuberculosis (TB) drug SQ109 (1), which has been reported to act by inhibiting a transporter called MmpL3, involved in cell wall biosynthesis. We show that 1 and the new compounds also target enzymes involved in menaquinone biosynthesis and electron transport, inhibiting respiration and ATP biosynthesis, and are uncouplers, collapsing the pH gradient and membrane potential used to power transporters. The result of such multitarget inhibition is potent inhibition of TB cell growth, as well as very low rates of spontaneous drug resistance. Several targets are absent in humans but are present in other bacteria, as well as in malaria parasites, whose growth is also inhibited.
Novel drug target strategies against Mycobacterium tuberculosis Curr Op Microbiology 2008
The resurgence of drug resistant tuberculosis (TB) is a significant global healthcare challenge. Mycobacterium tuberculosis (MTB), TB's causative agent, evades the host immune system and drug regimes by entering prolonged periods of non-proliferation or dormancy. In infected individuals, the immune system sequesters MTB into structures called granulomas where the bacterium survives by shifting into a non-replicative state. Although still not well understood, progress has been made in characterizing the genetic program of MTB, activated by DosR (DevR) signal transduction that allows adaptation to the hypoxic, nutrient limiting granuloma microenvironment. Recent work, especially the identification genes involved in regulatory networks and the Enduring Hypoxic Response (EHR), hold promise for developing new drugs targeting dormancy phase MTB.
Discovery of Selective Menaquinone Biosynthesis Inhibitors against Mycobacterium tuberculosis
Journal of Medicinal Chemistry, 2012
Aurachin RE (1) is a strong antibiotic that was recently found to possess MenA (1,4-dihydroxy-2naphthoate prenyltransferase) and bacterial electron transport inhibitory activities. Aurachin RE is the only molecule in a series of aurachin natural products that has the chiral center in the alkyl side chain at C9′-position. To identify selective MenA inhibitors against Mycobacterium tuberculosis, a series of chiral molecules were designed based on the structures of previously identified MenA inhibitors and 1. The synthesized molecules were evaluated in in vitro assays including MenA enzyme and bacterial growth inhibitory assays. We could identify novel MenA inhibitors that showed significant increase in potency of killing non-replicating M. tuberculosis in the low oxygen recovery assay (LORA) without inhibiting other Gram-positive bacterial growth even at high concentrations. The MenA inhibitors reported here are useful new pharmacophores for the development of selective antimycobacterial agents with strong activity against non-replicating M. tuberculosis.
Molecular Microbiology, 2009
Understanding the basis of bacterial persistence in latent infections is critical for eradication of tuberculosis. Analysis of Mycobacterium tuberculosis mRNA expression in an in vitro model of nonreplicating persistence indicated that the bacilli require electron transport chain components and ATP synthesis for survival. Additionally, low mM concentrations of aminoalkoxydiphenylmethane derivatives inhibited both the aerobic growth and survival of non-replicating, persistent M. tuberculosis. Metabolic labelling studies and quantification of cellular menaquinone levels suggested that menaquinone synthesis, and consequently electron transport, is the target of the aminoalkoxydiphenylmethane derivatives. This hypothesis is strongly supported by the observations that treatment with these compounds inhibits oxygen consumption and that supplementation of growth medium with exogenous menaquinone rescued both growth and oxygen consumption of treated bacilli. In vitro assays indicate that the aminoalkoxydiphenylmethane derivatives specifically inhibit MenA, an enzyme involved in the synthesis of menaquinone. Thus, the results provide insight into the physiology of mycobacterial persis-tence and a basis for the development of novel drugs that enhance eradication of persistent bacilli and latent tuberculosis.
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Potential drug targets in Mycobacterium tuberculosis through metabolic pathway analysis
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International Journal of Evolutionary Biology, 2014
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Virtual Screening of Compounds Against Mycobacterium tuberculosis Maltosyltransferase GlgE
Acta Scientific Pharmaceutical Sciences, 2019
The prevalence of tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) particularly the occurrence of multi-drug resistant and extensively-drug resistant strains of Mtb has prompted intense efforts to develop new anti-TB drugs. The enzyme maltosyltransferase GlgE of M. tuberculosis was determined to be a potential drug target. In this work, homology model of Mtb maltosyltransferase GlgE was generated based on eight reported protein structures with similar amino acid sequence. A pharmacophore based on the model was used to screen two databases of natural products. The virtual screening top hit, F_2.726 with binding energy (BE) of-322.83 kcal/mol, and the natural substrate maltose (BE =-322.85 kcal/mol), have comparable binding affinity. The top hit, a phenylcyclohexenyl carbamimidic acid, was then subjected to in silico structure optimization by De Novo Evolution method and yielded five variants with better binding affinities. The study also indicates that the GlgE structures from Streptomyces coelicolor can be used as templates for designing the GlgE inhibitors of Mycobacterium tuberculosis. Tuberculosis, commonly abbreviated as TB, has been a perennial global health problem. It impairs the health of approximately 10 million people each year and is one of the ten leading causes of death worldwide. In the past five years, it has overtaken HIV/AIDS as the number one cause of death by a single infectious agent [1]. In 2017, 6.4 million new cases of TB with 1.3 million deaths were reported to WHO. The United Nations (UN) meeting in September 2018, a first high-level meeting on TB, underscores the need for immediate response towards the global goal of eradicating the TB epidemic by 2030. TB is an infectious disease caused by Mycobacterium tuberculosis which affects primarily the lungs and also other extrapulmonary sites. It is easily transmitted through airborne droplets that proceed to infect mainly the tracheal pathways. A number of drug treatments (i.e. Isoniazid, Rifampicin, Ethambutol, etc.) are already available but the emergence of resistance to available drugs has made tuberculosis a continuous health threat worldwide [2]. Multi-drug resistant TB (MDR-TB), defined as TB resistant to the two most potent first-line anti-TB drugs (i.e. Rifampicin and Isoniazid), and extremely drug-resistant TB (XDR-TB), defined as MDR-TB resistant to any fluoroquinolone and at least one second-line injectable drug such as capreomycin, kanamycin, or amikacin [3,4], are not only prevalent in highly populated countries [5,6] but also pose additional challenges for effective control of TB in many parts of the world [1]. As resistance to anti-TB drugs continue to rise, there is a growing need to develop new classes of antitubercular agents. A genetically validated target in Mtb is maltosyltransferase GlgE, an important enzyme in the α-glucan pathway of M. tuberculosis. α-glucan in mycobacteria is exclusively synthesized intracellularly using α-maltose-1-phosphate as the substrate for the maltosyltransferase GlgE [7]. The inhibition of GlgE does not only lead to failure of biosynthesis of α-glucan, the main constituent of the mycobacterial capsule that is thought to be involved in immune evasion and virulence, but also the toxic accumulation of maltose-1-phosphate, that eventually leads to cell death [8].