Abstract
Conventional treatments to combat the tuberculosis (TB) epidemic are falling short, thus encouraging the search for novel antitubercular drugs acting on unexplored molecular targets. Several whole-cell phenotypic screenings have delivered bioactive compounds with potent antitubercular activity. However, their cellular target and mechanism of action remain largely unknown. Further evaluation of these compounds may include their screening in search for known antitubercular drug targets hits. Here, a collection of nearly 1400 mycobactericidal compounds was screened against Mycobacterium tuberculosis NaMN adenylyltransferase (MtNadD), a key enzyme in the biogenesis of NAD cofactor that was recently validated as a new drug target for dormant and active tuberculosis. We found three chemotypes that efficiently inhibit MtNadD in the low micromolar range in vitro. SAR and cheminformatics studies of commercially available analogues point to a series of benzimidazolium derivatives, here named N2, with bactericidal activity on different mycobacteria, including M. abscessus, multidrug-resistant M. tuberculosis, and dormant M. smegmatis. The on-target activity was supported by the increased resistance of an M. smegmatis strain overexpressing the target and by a rapid decline in NAD(H) levels. A cocrystal structure of MtNadD with N2-8 inhibitor reveals that the binding of the inhibitor induced the formation of a new quaternary structure, a dimer-of-dimers where two copies of the inhibitor occupy symmetrical positions in the dimer interface, thus paving the way for the development of a new generation of selective MtNadD bioactive inhibitors. All these results strongly suggest that pharmacological inhibition of MtNadD is an effective strategy to combat dormant and resistant Mtb strains.
Original language | English |
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Pages (from-to) | 949-958 |
Number of pages | 10 |
Journal | ACS Chemical Biology |
Volume | 14 |
Issue number | 5 |
DOIs | |
State | Published - May 17 2019 |
Bibliographical note
Publisher Copyright:© 2019 American Chemical Society.
Funding
We thank the Global Alliance for TB Drug Development (TB Alliance) for providing the TB whole cell active compounds library (TBAC). We are grateful to Eric Rubin (Harvard Medical School) for consultations on mycobacterial physiology and drug discovery. We want to thank L. Brumsey for constructing MtNadD overexpressing M. smegmatis strains. We thank the staff members of Southeast Regional Collaborative Access Team (SER-CAT) at the Advanced Photon Source, Argonne National Laboratory, for assistance during data collection. Use of the Advanced Photon Source was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. W-31-109-Eng-38. Research reported in this publication was partially supported by the National Institute of Allergy, and Infectious Diseases grant number R03AI117361 to KVK, Montalcini International Program 2009 and Grant RSA2013-14 through the Italian Ministry of Education, Universities, and Research to L.S., and the Lead Generation Initiative to A.O. and E.S. at SBP.
Funders | Funder number |
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U.S. Department of Energy EPSCoR | |
National Institute of Allergy and Infectious Diseases | R03AI117361, RSA2013-14 |
National Institute of Allergy and Infectious Diseases | |
Office of Science Programs | |
DOE Basic Energy Sciences | W-31-109-Eng-38 |
DOE Basic Energy Sciences | |
Ministero dell’Istruzione, dell’Università e della Ricerca |
ASJC Scopus subject areas
- Biochemistry
- Molecular Medicine