title: Novel insights into the mechanism of inhibition of MmpL3, a target of multiple pharmacophores in Mycobacterium tuberculosis.
abstract: MmpL3, a resistance-nodulation-division (RND) superfamily transporter, has been implicated in the formation of the outer membrane of Mycobacterium tuberculosis; specifically, MmpL3 is required for the export of mycolic acids in the form of trehalose monomycolates (TMM) to the periplasmic space or outer membrane of M. tuberculosis. Recently, seven series of inhibitors identified by whole-cell screening against M. tuberculosis, including the antituberculosis drug candidate SQ109, were shown to abolish MmpL3-mediated TMM export. However, this mode of action was brought into question by the broad-spectrum activities of some of these inhibitors against a variety of bacterial and fungal pathogens that do not synthesize mycolic acids. This observation, coupled with the ability of three of these classes of inhibitors to kill nonreplicating M. tuberculosis bacilli, led us to investigate alternative mechanisms of action. Our results indicate that the inhibitory effects of adamantyl ureas, indolecarboxamides, tetrahydropyrazolopyrimidines, and the 1,5-diarylpyrrole BM212 on the transport activity of MmpL3 in actively replicating M. tuberculosis bacilli are, like that of SQ109, most likely due to their ability to dissipate the transmembrane electrochemical proton gradient. In addition to providing novel insights into the modes of action of compounds reported to inhibit MmpL3, our results provide the first explanation for the large number of pharmacophores that apparently target this essential inner membrane transporter.
authors.affiliation: Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Upadhyay
authors.affiliation: Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Fabio L
authors.initials: FL
authors.lastname: Fontes
authors.affiliation: Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
authors.forename: E Jeffrey
authors.initials: EJ
authors.lastname: North
authors.affiliation: Institute for Tuberculosis Research, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois, USA.
authors.forename: Yuehong
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Chemistry, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Debbie C
authors.initials: DC
authors.lastname: Crans
authors.affiliation: Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Anna E
authors.initials: AE
authors.lastname: Grzegorzewicz
authors.affiliation: Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Victoria
authors.initials: V
authors.lastname: Jones
authors.affiliation: Institute for Tuberculosis Research, College of Pharmacy, University of Illinois at Chicago, Chicago, Illinois, USA.
authors.forename: Scott G
authors.initials: SG
authors.lastname: Franzblau
authors.affiliation: Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Lee
authors.affiliation: Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA dean.crick@colostate.edu mary.jackson@colostate.edu.
authors.forename: Dean C
authors.initials: DC
authors.lastname: Crick
authors.affiliation: Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA dean.crick@colostate.edu mary.jackson@colostate.edu.
authors.forename: Mary
authors.initials: M
authors.lastname: Jackson
mesh_terms: D000218:Adamantane / Q000031:analogs & derivatives* / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000995:Antitubercular Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors; D002462:Cell Membrane; D003311:Cord Factors / Q000378:metabolism; D024901:Drug Resistance, Multiple, Bacterial; D005029:Ethylenediamines / Q000494:pharmacology*; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D026901:Membrane Transport Proteins; D008826:Microbial Sensitivity Tests; D020102:Mycobacterium smegmatis / Q000187:drug effects*; D009169:Mycobacterium tuberculosis / Q000187:drug effects*; D009171:Mycolic Acids / Q000378:metabolism; D010671:Phenylurea Compounds / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D061209:Proton Ionophores / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology; D018088:Tuberculosis, Multidrug-Resistant / Q000188:drug therapy / Q000382:microbiology; D014634:Valinomycin / Q000494:pharmacology; D024482:Vitamin K 2 / Q000378:metabolism
chemical_list: C572246:1-(2-adamantyl)-3-(2,3,4-trifluorophenyl)urea; D000900:Anti-Bacterial Agents; D000995:Antitubercular Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D003311:Cord Factors; D005029:Ethylenediamines; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C000599913:MmpL3 protein, Mycobacterium tuberculosis; D009171:Mycolic Acids; C506841:N-geranyl-N'-(2-adamantyl)ethane-1,2-diamine; D010671:Phenylurea Compounds; D010879:Piperazines; D061209:Proton Ionophores; D011758:Pyrroles; C021099:trehalose monomycolate; D024482:Vitamin K 2; D014634:Valinomycin; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D000218:Adamantane; C115651:BM 212