The natural product cyclomarin kills Mycobacterium tuberculosis by targeting the ClpC1 subunit of the caseinolytic protease

Tuberculosis presents a major global health challenge. With the expansion of drug resistance and the spread of extremely-drug resistant Mycobacterium tuberculosis strains, the identification of novel drug targets has become paramount. Here we show that the ATP-dependent chaperone ClpC1 is the target of cyclomarin, a potent anti-mycobacterial natural product. Our findings validate the Clp protease as a novel drug target in Mtb in both growing and hypoxic non-growing bacteria

FR171456 is a specific inhibitor of mammalian NSDHL and yeast Erg26p

FR171456 is a natural product with cholesterol-lowering properties in animal models, but its molecular target is unknown, which hinders further drug development. Here we show that FR171456 specifically targets the sterol-4-alpha-carboxylate-3-dehydrogenase (Saccharomyces cerevisiae—Erg26p, Homo sapiens—NSDHL (NAD(P) dependent steroid dehydrogenase-like)), an essential enzyme in the ergosterol/cholesterol biosynthesis pathway. FR171456 significantly alters the levels of cholesterol pathway intermediates in human and yeast cells. Genome-wide yeast haploinsufficiency profiling experiments highlight the erg26/ERG26 strain, and multiple mutations in ERG26 confer resistance to FR171456 in growth and enzyme assays. Some of these ERG26 mutations likely alter Erg26 binding to FR171456, based on a model of Erg26. Finally, we show that FR171456 inhibits an artificial Hepatitis C viral replicon, and has broad antifungal activity, suggesting potential additional utility as an anti-infective. The discovery of the target and binding site of FR171456 within the target will aid further development of this compound

Oxysterols direct immune cell migration through EBI2

Epstein-Barr virus (EBV)-induced gene 2 (EBI2, aka GPR183) is a G protein-coupled receptor that is required for humoral immune responses and polymorphisms in the receptor have been associated with inflammatory autoimmune diseases1-3. The natural ligand for EBI2 has been unknown. Here we describe identification of 7, 25-dihydroxycholesterol (5-cholesten-3, 7, 25-triol; 7, 25-OHC) as a potent and selective agonist of EBI2. Functional activation of EBI2 by 7, 25-OHC and closely related oxysterols was verified by monitoring second messenger readouts and saturable, high affinity radioligand binding. Furthermore we find that 7, 25-OHC and closely related oxysterols act as chemoattractants for immune cells expressing EBI2 by directing cell migration in vitro and in vivo. A key enzyme required for the generation of 7, 25-OHC is cholesterol 25-hydroxylase (Ch25h)4. Similar to EBI2 receptor knockout mice, mice deficient in Ch25h fail to position activated B cells within the spleen to the outer follicle and mount a reduced plasma cell response after an immune challenge. This demonstrates that Ch25h generates EBI2 bioactivity in vivo and suggests that the EBI2 oxysterol signaling pathway plays an important role in the adaptive immune response

Potent Nonimmunosuppressive Cyclophilin Inhibitors With Improved Pharmaceutical Properties and Decreased Transporter Inhibition

Nonimmunosuppressive cyclophilin inhibitors have demonstrated efficacy for the treatment of hepatitis C infection (HCV). However, alisporivir, cyclosporin A, and most other cyclosporins are potent inhibitors of OATP1B1, MRP2, MDR1, and other important drug transporters. Reduction of the side chain hydrophobicity of the P4 residue preserves cyclophilin binding and antiviral potency while decreasing transporter inhibition. Representative inhibitor <b>33</b> (NIM258) is a less potent transporter inhibitor relative to previously described cyclosporins, retains anti-HCV activity in cell culture, and has an acceptable pharmacokinetic profile in rats and dogs. An X-ray structure of <b>33</b> bound to rat cyclophilin D is reported