Tuberculosis is the deadliest infectious disease in history and new drugs are urgently required to combat multidrug-resistant (MDR) strains of Mycobacterium tuberculosis (Mtb). Here, we exploit the relience of Mtb on host-derived cholesterol to develop a novel class of antitubercular compounds that target Mtb CYP125 and CYP142; the enzymes that catalyze the first step of cholesterol metabolism. A combination of fragment screening and structure-based drug design was used to identify a hit compound and guide synthetic optimization of a dual CYP125/142 ligand 5m (KD 40-160 nM), which potently inhibits enzyme activity in vitro (KI < 100 nM), and the growth of Mtb in extracellular (MIC99 0.4-1.5 μM) and intracellular assays (IC50 1.7 μM). The structural data and lead compounds reported here will help study Mtb cholesterol metabolism and guide the development of novel antibiotics to combat MDR Mtb.

AbstractMycobacterium tuberculosis(Mtb) is the world’s most deadly infectious pathogen and new drugs are urgently required to combat the emergence of multi-(MDR) and extensively-(XDR) drug resistant strains. The bacterium specifically upregulates sterol uptake pathways in infected macrophages and the metabolism of host-derived cholesterol is essential forMtb’slong-term survivalin vivo.Here, we report the development of antitubercular small molecules that inhibit theMtbcholesterol oxidases CYP125 and CYP142, which catalyze the initial step of cholesterol metabolism. An efficient biophysical fragment screen was used to characterize the structure-activity relationships of CYP125 and CYP142, and identify a non-azole small molecule1athat can bind to the heme cofactor of both enzymes. A structure-guided fragment-linking strategy was used to optimize the binding affinity of1a, yielding a potent dual CYP125/142 inhibitor5m(KDCYP125/CYP142 = 0.04/0.16 µM). Compound5mpotently inhibits the catalytic activity of CYP125 and CYP142in vitro(KIvalues < 0.1 µM), and rapidly depletesMtbintracellular ATP (IC50= 0.15 µM). The compound has antimicrobial activity against both drug susceptible and MDRMtb (MIC99values 0.4 - 1.5 µM)in extracellular assays, and inhibits the growth ofMtbin human macrophages (MIC = 1.7 µM) with good selectivity over mammalian cytotoxicity (LD50≥ 50 µM). The combination of small molecule inhibitors and structural data reported here provide useful tools to study the role of cholesterol metabolism inMtband are a promising step towards novel antibiotics targeting bioenergetic pathways, which could be used to help combat MDR-TB.

Cells rely on antioxidants to survive. The most abundant antioxidant is glutathione (GSH). The synthesis of GSH is non-redundantly controlled by the glutamate-cysteine ligase catalytic subunit (GCLC). GSH imbalance is implicated in many diseases, but the requirement for GSH in adult tissues is unclear. To interrogate this, we have developed a series of in vivo models to induce Gclc deletion in adult animals. We find that GSH is essential to lipid abundance in vivo. GSH levels are highest in liver tissue, which is also a hub for lipid production. While the loss of GSH does not cause liver failure, it decreases lipogenic enzyme expression, circulating triglyceride levels, and fat stores. Mechanistically, we find that GSH promotes lipid abundance by repressing NRF2, a transcription factor induced by oxidative stress. These studies identify GSH as a fulcrum in the liver's balance of redox buffering and triglyceride production.

Abstract Glutathione (GSH), the most abundant antioxidant, scavenges free radicals and prevents the detrimental effects of oxidative stress. As a result, GSH levels are associated with protection from stress-related conditions, such as aging and cancer. Given this rationale, antioxidants are routinely consumed by the public, mainly because they are viewed as “cure-alls” and almost uniformly beneficial to a range of diseases. This is an oversimplification, as the relationship between antioxidants and diseases is much more complex. Recent evidence has implicated GSH in protecting cancer cells from oxidative stress and promoting their survival. Therefore, understanding GSH metabolism in vivo and its intricate crosstalk with other cellular pathways is vital to improving the efficacy of therapies for diseases, including cancer. To interrogate this, we developed a series of in vivo models to induce Gclc deletion in adult animals. We find that GSH is essential to lipid abundance in vivo. GSH levels are reported to be highest in liver tissue, which is also a hub for lipid production. While the loss of GSH did not cause liver failure, it decreased lipogenic enzyme expression, circulating triglyceride levels, and fat stores. Mechanistically, we found that GSH promotes lipid abundance via the LXR/SREBP signaling pathway, as well as by repressing NRF2, a transcription factor induced by oxidative stress. Overall, these findings suggest an essential function for GSH in maintaining circulating lipids levels and lipid depots, possibly as a mechanism to prevent lipid peroxidation and redox imbalances. Notably, the accumulation of oxidized lipids propagates oxidative stress and associated cell death phenotypes (i.e., ferroptosis). This also highlights a potentially novel mechanism by which GSH regulates lipid production and suggests a possible link between oxidative stress (caused by GSH deficiency) and cachexia (commonly characterized by loss of fat and lean mass), a disorder linked to cancer but poorly understood. Consequently, by elucidating the contributions of GSH to lipid homeostasis, we can better understand the basic biology surrounding GSH and obtain critical insight into potentially improving the treatment of cancer-related cachexia. Citation Format: Gloria Asantewaa, Emily T. Tuttle, Nathan P. Ward, Yun P. Kang, Yumi Kim, Madeline Kavanagh, Aaron R. Huber, Joshua Munger, Benjamin Cravatt, Calvin L. Cole, Gina M. DeNicola, Isaac S. Harris. Glutathione supports lipid abundance in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB292.

Cells rely on antioxidants to survive. The most abundant antioxidant is glutathione (GSH). The synthesis of GSH is non-redundantly controlled by the glutamate-cysteine ligase catalytic subunit (GCLC). GSH imbalance is implicated in many diseases, but the requirement for GSH in adult tissues is unclear. To interrogate this, we developed a series of in vivo models to induce Gclc deletion in adult animals. We find that GSH is essential to lipid abundance in vivo. GSH levels are reported to be highest in liver tissue, which is also a hub for lipid production. While the loss of GSH did not cause liver failure, it decreased lipogenic enzyme expression, circulating triglyceride levels, and fat stores. Mechanistically, we found that GSH promotes lipid abundance by repressing NRF2, a transcription factor induced by oxidative stress. These studies identify GSH as a fulcrum in the liver’s balance of redox buffering and triglyceride production.

Mycobacterium tuberculosis (Mtb) was responsible for approximately 1.6 million deaths in 2021. With the emergence of extensive drug resistance, novel therapeutic agents are urgently needed, and continued drug discovery efforts required. Host-derived lipids such as cholesterol not only support Mtb growth, but are also suspected to function in immunomodulation, with links to persistence and immune evasion. Mtb cytochrome P450 (CYP) enzymes facilitate key steps in lipid catabolism and thus present potential targets for inhibition. Here we present a series of compounds based on an ethyl 5-(pyridin-4-yl)-1H-indole-2-carboxylate pharmacophore which bind strongly to both Mtb cholesterol oxidases CYP125 and CYP142. Using a structure-guided approach, combined with biophysical characterization, compounds with micromolar range in-cell activity against clinically relevant drug-resistant isolates were obtained. These will incite further development of much-needed additional treatment options and provide routes to probe the role of CYP125 and CYP142 in Mtb pathogenesis.

The Janus tyrosine kinase (JAK) family of non-receptor tyrosine kinases includes four isoforms (JAK1, JAK2, JAK3, and TYK2) and is responsible for signal transduction downstream of diverse cytokine receptors. JAK inhibitors have emerged as important therapies for immun(onc)ological disorders, but their use is limited by undesirable side effects presumed to arise from poor isoform selectivity, a common challenge for inhibitors targeting the ATP-binding pocket of kinases. Here we describe the chemical proteomic discovery of a druggable allosteric cysteine present in the non-catalytic pseudokinase domain of JAK1 (C817) and TYK2 (C838), but absent from JAK2 or JAK3. Electrophilic compounds selectively engaging this site block JAK1-dependent trans-phosphorylation and cytokine signaling, while appearing to act largely as 'silent' ligands for TYK2. Importantly, the allosteric JAK1 inhibitors do not impair JAK2-dependent cytokine signaling and are inactive in cells expressing a C817A JAK1 mutant. Our findings thus reveal an allosteric approach for inhibiting JAK1 with unprecedented isoform selectivity.

The JAK family of non-receptor tyrosine kinases includes four subtypes (JAK1, JAK2, JAK3, and TYK2) and is responsible for signal transduction downstream of diverse cytokine receptors. JAK inhibitors have emerged as important therapies for immuno(onc)ological disorders, but their use is limited by undesirable side effects presumed to arise from poor subtype selectivity, a common challenge for inhibitors targeting the ATP-binding pocket of kinases. Here, we describe the chemical proteomic discovery of a druggable allosteric cysteine present in the non-catalytic pseudokinase domain of JAK1 (C817) and TYK2 (C838), but absent from JAK2 or JAK3. Electrophilic compounds selectively engaging this site block JAK1-dependent transphosphorylation and cytokine signaling, while appearing to act largely as “silent” ligands for TYK2. Importantly, the allosteric JAK1 inhibitors do not impair JAK2-dependent cytokine signaling and are inactive in cells expressing a C817A JAK1 mutant. Our findings thus reveal an allosteric approach for inhibiting JAK1 with unprecedented subtype selectivity.

There is a pressing need for new drugs against tuberculosis (TB) to combat the growing resistance to current antituberculars. Herein a novel strategy is described for hit generation against promising TB targets involving X-ray crystallographic screening in combination with phenotypic screening. This combined approach (XP Screen) affords both a validation of target engagement as well as determination of in cellulo activity. The utility of this method is illustrated by way of an XP Screen against CYP121A1, a cytochrome P450 enzyme from Mycobacterium tuberculosis (Mtb) championed as a validated drug discovery target. A focused screening set was synthesized and tested by such means, with several members of the set showing promising activity against Mtb strain H37Rv. One compound was observed as an X-ray hit against CYP121A1 and showed improved activity against Mtb strain H37Rv under multiple assay conditions (pan-assay activity). Data obtained during X-ray crystallographic screening were utilized in a structure-based campaign to design a limited number of analogues (less than twenty), many of which also showed pan-assay activity against Mtb strain H37Rv. These included the benzo[b][1,4]oxazine derivative (MIC90 6.25 μM), a novel hit compound suitable as a starting point for a more involved hit to lead candidate medicinal chemistry campaign.

Carbapenems are vital antibiotics, but their efficacy is increasingly compromised by metallo-β-lactamases (MBLs). Here we report the discovery and optimization of potent broad-spectrum MBL inhibitors. A high-throughput screen for NDM-1 inhibitors identified indole-2-carboxylates (InCs) as potential β-lactamase stable β-lactam mimics. Subsequent structure–activity relationship studies revealed InCs as a new class of potent MBL inhibitor, active against all MBL classes of major clinical relevance. Crystallographic studies revealed a binding mode of the InCs to MBLs that, in some regards, mimics that predicted for intact carbapenems, including with respect to maintenance of the Zn(II)-bound hydroxyl, and in other regards mimics binding observed in MBL–carbapenem product complexes. InCs restore carbapenem activity against multiple drug-resistant Gram-negative bacteria and have a low frequency of resistance. InCs also have a good in vivo safety profile, and when combined with meropenem show a strong in vivo efficacy in peritonitis and thigh mouse infection models. The efficacy of carbapenem antibiotics can be compromised by metallo-β-lactamases, but a high-throughput screen followed by optimization has now enabled the discovery of indole-2-carboxylates (InCs) as potent broad-spectrum metallo-β-lactamase inhibitors. The results highlight the potential of InC–carbapenem combinations for clinical use as well as mechanism-guided approaches to combatting globally disseminated antibiotic resistant mechanisms.

Recent advances in chemical proteomics have begun to characterize the reactivity and ligandability of lysines on a global scale. Yet, only a limited diversity of aminophilic electrophiles have been evaluated for interactions with the lysine proteome. Here, we report an in-depth profiling of >30 uncharted aminophilic chemotypes that greatly expands the content of ligandable lysines in human proteins. Aminophilic electrophiles showed disparate proteomic reactivities that range from selective interactions with a handful of lysines to, for a set of dicarboxaldehyde fragments, remarkably broad engagement of the covalent small-molecule-lysine interactions captured by the entire library. We used these latter 'scout' electrophiles to efficiently map ligandable lysines in primary human immune cells under stimulatory conditions. Finally, we show that aminophilic compounds perturb diverse biochemical functions through site-selective modification of lysines in proteins, including protein-RNA interactions implicated in innate immune responses. These findings support the broad potential of covalent chemistry for targeting functional lysines in the human proteome.

Similarity in the ligand binding profile of two enzymes may provide insight for functional characterization and be of greater relevance to inhibitor development than sequence similarity or structural homology. Fragment screening is an efficient approach to characterizing the ligand profile of an enzyme and has been applied here to study the family of cytochrome P450 enzymes (P450s) expressed by Mycobacterium tuberculosis (Mtb). The Mtb P450s have important roles in bacterial virulence, survival and pathogenicity. Comparing the fragment profiles of seven of these enzymes revealed that P450s which share a similar biological function have significantly similar fragment profiles, while functionally unrelated or orphan P450s exhibit distinct ligand binding properties, despite overall high structural homology. Chemical structures that exhibit promiscuous binding between enzymes have been identified, as have selective fragments that could provide leads for inhibitor development. The similarity in the fragment binding profile of the orphan enzyme CYP144A1 to CYP121A1, an enzyme important for Mtb viability, provides a case study illustrating the subsequent identification of novel CYP144A1 ligands. The different binding modes of these compounds to CYP144A1 provide insight into structural and dynamic aspects of the enzyme, suggest a hypothesis into biological function and provide opportunity for inhibitor development. Expanding this fragment profiling approach to include a greater number of functionally characterized and orphan proteins may provide a valuable resource for understanding enzyme-ligand interactions.

Similarity between the ligand binding profiles of enzymes may aid functional characterization and be of greater relevance to inhibitor development than sequence similarity or structural homology. Fragment screening is an efficient approach for characterization of the ligand binding profile of an enzyme and has been applied here to study the family of cytochrome P450 enzymes (P450s) expressed by Mycobacterium tuberculosis (Mtb). The Mtb P450s have important roles in bacterial virulence, survival, and pathogenicity. Comparing the fragment profiles of seven of these enzymes revealed that P450s which share a similar biological function have significantly similar fragment profiles, whereas functionally unrelated or orphan P450s exhibit distinct ligand binding properties, despite overall high structural homology. Chemical structures that exhibit promiscuous binding between enzymes have been identified, as have selective fragments that could provide leads for inhibitor development. The similarity between the fragment binding profiles of the orphan enzyme CYP144A1 and CYP121A1, a characterized enzyme that is important for Mtb viability, provides a case study illustrating the subsequent identification of novel CYP144A1 ligands. The different binding modes of these compounds to CYP144A1 provide insight into structural and dynamic aspects of the enzyme, possible biological function, and provide the opportunity to develop inhibitors. Expanding this fragment profiling approach to include a greater number of functionally characterized and orphan proteins may provide a valuable resource for understanding enzyme-ligand interactions.

Given the frequent use of DMSO in biochemical and biophysical assays, it is desirable to understand the influence of DMSO concentration on the dissociation or unfolding behavior of proteins. In this study, the effects of DMSO on the structure and interactions of avidin and Mycobacterium tuberculosis (Mtb) CYP142A1 were assessed through collision-induced dissociation (CID) and collision-induced unfolding (CIU) as monitored by nanoelectrospray ionization-ion mobility-mass spectrometry (nESI-IM-MS). DMSO concentrations higher than 4% (v/v) destabilize the avidin tetramer toward dissociation and unfolding, via both its effects on charge state distribution (CSD) as well as at the level of individual charge states. In contrast, DMSO both protects against heme loss and increases the stability of CYP142A1 toward unfolding even up to 40% DMSO. Tandem MS/MS experiments showed that DMSO could modify the dissociation pathway of CYP142A1, while CIU revealed the protective effect of the heme group on the structure of CYP142A1.

This data is submitted in support of the manuscript entitled Substrate fragmentation for the design of M. tuberculosis CYP121 inhibitors, which has been accepted for publication in the journal ChemMedChem, and has the DOI: 10.1002/cmdc.201600248. The characterisation data (IR, HRMS, LCMS, NMR) for compounds synthesised in this research are provided as PDF files. The EPR (narrow and wide scan) raw data is provided for compounds as csv files. The difference spectra for the titration of CYP121 with the ligands described in the study are provided as csv files.

Supporting data for the article Fragment-based approaches to the development of Mycobacterium tuberculosis CYP121 inhibitors, published in the Journal of Medicinal Chemistry, 2016. LCMS, HRMS, IR and NMR spectra from the characterisation of compounds reported in the Experimental Methods section of the article are provided as PDFs. Isothermal titration calorimetry enthalpy plots and data fitting for compounds reported in Table 2 of the article are provided as PDFs. Data for human cytochrome P450 inhibition studies with compounds 19a, 25a and 26a provided as a PDF.