A crucial component in the ability of Mtb to survive in bactericidal environments such as the phagosome of macrophages is the efficient permeability barrier established by its unusual outer membrane (OM). We have discovered that an Mtb mutant lacking the OM channel protein Rv1698 was more susceptible to copper. Copper is an essential micronutrient, but excess copper is toxic. The intracellular copper concentration of the rv1698 mutant was 100-fold increased. Our experiments demonstrated that Rv1698 is required for copper efflux across the OM and for maintaining low intracellular copper levels. Because efflux against a concentration gradient requires energy, the OM component of efflux systems in E. coli is connected to an inner membrane pump which contributes substrate specificity and energy to the transport process. However, it is unknown how Mtb extrudes waste molecules, drugs, and other toxic solutes. Rv1698 is the first OM component of any efflux system in mycobacteria and, hence, represents a great opportunity not only to examine how Mtb controls essential, but toxic redox-active metals such as copper, but also efflux processes in Mtb in general. Copper inside Mtb-containing phagosomes is increased upon stimulation of macrophages with interferon-3 to concentrations that are sufficient to inhibit growth of Mtb indicating that copper homeostasis is critical for virulence of Mtb. However, this is a largely unexplored field for Mtb. We, therefore, propose to characterize the novel copper efflux channel MctB and interacting proteins, to identify missing components of copper homeostasis and to assess their role in virulence of Mtb.

Public Health Relevance

Scientific interest in mycobacteria has not only been sparked by the paramount medical importance of Mycobacterium tuberculosis but also by its unusual outer membrane which is a crucial component in its ability to survive in bactericidal environments. We have discovered that a novel outer membrane channel protein of M. tuberculosis is required for efflux of copper. This protein is surface-accessible and represents the first outer membrane component of any efflux system in mycobacteria.

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National Institute of Allergy and Infectious Diseases (NIAID)
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Bacterial Pathogenesis Study Section (BACP)
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Lacourciere, Karen A
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University of Alabama Birmingham
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Sun, Jim; Siroy, Axel; Lokareddy, Ravi K et al. (2015) The tuberculosis necrotizing toxin kills macrophages by hydrolyzing NAD. Nat Struct Mol Biol 22:672-8
Danilchanka, Olga; Pires, David; Anes, Elsa et al. (2015) The Mycobacterium tuberculosis outer membrane channel protein CpnT confers susceptibility to toxic molecules. Antimicrob Agents Chemother 59:2328-36
Speer, Alexander; Sun, Jim; Danilchanka, Olga et al. (2015) Surface hydrolysis of sphingomyelin by the outer membrane protein Rv0888 supports replication of Mycobacterium tuberculosis in macrophages. Mol Microbiol 97:881-97
Dalecki, Alex G; Haeili, Mehri; Shah, Santosh et al. (2015) Disulfiram and Copper Ions Kill Mycobacterium tuberculosis in a Synergistic Manner. Antimicrob Agents Chemother 59:4835-44
Neyrolles, Olivier; Wolschendorf, Frank; Mitra, Avishek et al. (2015) Mycobacteria, metals, and the macrophage. Immunol Rev 264:249-63
Jones, Christopher M; Wells, Ryan M; Madduri, Ashoka V R et al. (2014) Self-poisoning of Mycobacterium tuberculosis by interrupting siderophore recycling. Proc Natl Acad Sci U S A 111:1945-50
Danilchanka, Olga; Sun, Jim; Pavlenok, Mikhail et al. (2014) An outer membrane channel protein of Mycobacterium tuberculosis with exotoxin activity. Proc Natl Acad Sci U S A 111:6750-5
Jones, Christopher M; Niederweis, Michael (2014) Organ pathology in the absence of bacteria? J Infect Dis 209:971
Speer, Alexander; Rowland, Jennifer L; Haeili, Mehri et al. (2013) Porins increase copper susceptibility of Mycobacterium tuberculosis. J Bacteriol 195:5133-40
Wells, Ryan M; Jones, Christopher M; Xi, Zhaoyong et al. (2013) Discovery of a siderophore export system essential for virulence of Mycobacterium tuberculosis. PLoS Pathog 9:e1003120

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