title: Antigen 85C inhibition restricts Mycobacterium tuberculosis growth through disruption of cord factor biosynthesis.
abstract: The antigen 85 (Ag85) protein family, consisting of Ag85A, -B, and -C, is vital for Mycobacterium tuberculosis due to its role in cell envelope biogenesis. The mycoloyl transferase activity of these proteins generates trehalose dimycolate (TDM), an envelope lipid essential for M. tuberculosis virulence, and cell wall arabinogalactan-linked mycolic acids. Inhibition of these enzymes through substrate analogs hinders growth of mycobacteria, but a link to mycolic acid synthesis has not been established. In this study, we characterized a novel inhibitor of Ag85C, 2-amino-6-propyl-4,5,6,7-tetrahydro-1-benzothiophene-3-carbonitrile (I3-AG85). I3-AG85 was isolated from a panel of four inhibitors that exhibited structure- and dose-dependent inhibition of M. tuberculosis division in broth culture. I3-AG85 also inhibited M. tuberculosis survival in infected primary macrophages. Importantly, it displayed an identical MIC against the drug-susceptible H37Rv reference strain and a panel of extensively drug-resistant/multidrug-resistant M. tuberculosis strains. Nuclear magnetic resonance analysis indicated binding of I3-AG85 to Ag85C, similar to its binding to the artificial substrate octylthioglucoside. Quantification of mycolic acid-linked lipids of the M. tuberculosis envelope showed a specific blockade of TDM synthesis. This was accompanied by accumulation of trehalose monomycolate, while the overall mycolic acid abundance remained unchanged. Inhibition of Ag85C activity also disrupted the integrity of the M. tuberculosis envelope. I3-AG85 inhibited the division of and reduced TDM synthesis in an M. tuberculosis strain deficient in Ag85C. Our results indicate that Ag85 proteins are promising targets for novel antimycobacterial drug design.
authors.affiliation: Department of Immunology, Max Planck Institute for Infection Biology, Berlin, Germany.
authors.forename: Thulasi
authors.initials: T
authors.lastname: Warrier
authors.forename: Marielle
authors.initials: M
authors.lastname: Tropis
authors.forename: Jim
authors.initials: J
authors.lastname: Werngren
authors.forename: Anne
authors.initials: A
authors.lastname: Diehl
authors.forename: Martin
authors.initials: M
authors.lastname: Gengenbacher
authors.forename: Brigitte
authors.initials: B
authors.lastname: Schlegel
authors.forename: Markus
authors.initials: M
authors.lastname: Schade
authors.forename: Hartmut
authors.initials: H
authors.lastname: Oschkinat
authors.forename: Mamadou
authors.initials: M
authors.lastname: Daffe
authors.forename: Sven
authors.initials: S
authors.lastname: Hoffner
authors.forename: Ali Nasser
authors.initials: AN
authors.lastname: Eddine
authors.forename: Stefan H E
authors.initials: SH
authors.lastname: Kaufmann
mesh_terms: D000217:Acyltransferases / Q000037:antagonists & inhibitors*; D000818:Animals; D000942:Antigens, Bacterial; D001854:Bone Marrow Cells / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003311:Cord Factors / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D003470:Culture Media; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D008055:Lipids / Q000096:biosynthesis; D008264:Macrophages / Q000187:drug effects; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D008810:Mice, Inbred C57BL; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000254:growth & development*; D010078:Oxazines; D011994:Recombinant Proteins / Q000096:biosynthesis; D013863:Thioglucosides / Q000494:pharmacology; D014498:Uracil / Q000378:metabolism; D014966:Xanthenes
chemical_list: D000942:Antigens, Bacterial; D003311:Cord Factors; D003470:Culture Media; D008055:Lipids; D010078:Oxazines; D011994:Recombinant Proteins; D013863:Thioglucosides; D014966:Xanthenes; C005843:resazurin; D014498:Uracil; C042989:n-octyl-beta-D-thioglucopyranoside; D000217:Acyltransferases; C119774:antigen 85C, Mycobacterium tuberculosis