RESUMO
Mycobacterium tuberculosis (Mtb) is the world's most deadly pathogen. Unlike less virulent mycobacteria, Mtb produces 1-tuberculosinyladenosine (1-TbAd), an unusual terpene nucleoside of unknown function. In the present study 1-TbAd has been shown to be a naturally evolved phagolysosome disruptor. 1-TbAd is highly prevalent among patient-derived Mtb strains, where it is among the most abundant lipids produced. Synthesis of TbAd analogs and their testing in cells demonstrate that their biological action is dependent on lipid linkage to the 1-position of adenosine, which creates a strong conjugate base. Furthermore, C20 lipid moieties confer passage through membranes. 1-TbAd selectively accumulates in acidic compartments, where it neutralizes the pH and swells lysosomes, obliterating their multilamellar structure. During macrophage infection, a 1-TbAd biosynthesis gene (Rv3378c) confers marked phagosomal swelling and intraphagosomal inclusions, demonstrating an essential role in regulating the Mtb cellular microenvironment. Although macrophages kill intracellular bacteria through phagosome acidification, Mtb coats itself abundantly with antacid.
Assuntos
Antiácidos/metabolismo , Lipídeos/biossíntese , Lipídeos/química , Mycobacterium tuberculosis/metabolismo , Fagossomos/metabolismo , Animais , Regulação Bacteriana da Expressão Gênica , Humanos , Concentração de Íons de Hidrogênio , Lisossomos , Macrófagos/metabolismo , Camundongos , Estrutura Molecular , Mycobacterium kansasii/genética , PrevalênciaAssuntos
Infecções Bacterianas/imunologia , Proteínas de Transporte de Cátions/fisiologia , Imunidade Celular/fisiologia , Macrófagos/imunologia , Elementos de Transição/metabolismo , Adenosina Trifosfatases/antagonistas & inibidores , Adenosina Trifosfatases/metabolismo , Animais , Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Bactérias/efeitos dos fármacos , Bactérias/enzimologia , Bactérias/patogenicidade , Infecções Bacterianas/tratamento farmacológico , Proteínas de Bactérias/antagonistas & inibidores , Proteínas de Bactérias/metabolismo , Transporte Biológico Ativo , Cobre/farmacologia , Cobre/fisiologia , Desenho de Fármacos , Humanos , Ferro/metabolismo , Ferro/farmacologia , Manganês/metabolismo , Manganês/farmacologia , Camundongos , Modelos Imunológicos , Fagocitose , Fagossomos/metabolismo , Fagossomos/microbiologia , Virulência , Zinco/metabolismo , Zinco/farmacologiaRESUMO
Mycobacterium tuberculosis thrives within macrophages by residing in phagosomes and preventing them from maturing and fusing with lysosomes. A parallel transcriptional survey of intracellular mycobacteria and their host macrophages revealed signatures of heavy metal poisoning. In particular, mycobacterial genes encoding heavy metal efflux P-type ATPases CtpC, CtpG, and CtpV, and host cell metallothioneins and zinc exporter ZnT1, were induced during infection. Consistent with this pattern of gene modulation, we observed a burst of free zinc inside macrophages, and intraphagosomal zinc accumulation within a few hours postinfection. Zinc exposure led to rapid CtpC induction, and ctpC deficiency caused zinc retention within the mycobacterial cytoplasm, leading to impaired intracellular growth of the bacilli. Thus, the use of P(1)-type ATPases represents a M. tuberculosis strategy to neutralize the toxic effects of zinc in macrophages. We propose that heavy metal toxicity and its counteraction might represent yet another chapter in the host-microbe arms race.
Assuntos
ATPases Bacterianas Próton-Translocadoras/metabolismo , Macrófagos/metabolismo , Mycobacterium tuberculosis/enzimologia , Tuberculose/metabolismo , Zinco/metabolismo , Animais , ATPases Bacterianas Próton-Translocadoras/genética , Células Cultivadas , Feminino , Humanos , Macrófagos/efeitos dos fármacos , Macrófagos/microbiologia , Camundongos , Camundongos Endogâmicos BALB C , Mycobacterium tuberculosis/genética , Mycobacterium tuberculosis/metabolismo , Tuberculose/microbiologia , Zinco/toxicidadeRESUMO
The C-type lectin dendritic cell-specific intercellular adhesion molecule-3 grabbing nonintegrin (DC-SIGN) mediates the innate immune recognition of microbial carbohydrates. We investigated the function of this molecule in the host response to pathogens in vivo, by generating mouse lines lacking the DC-SIGN homologues SIGNR1, SIGNR3, and SIGNR5. Resistance to Mycobacterium tuberculosis was impaired only in SIGNR3-deficient animals. SIGNR3 was expressed in lung phagocytes during infection, and interacted with M. tuberculosis bacilli and mycobacterial surface glycoconjugates to induce secretion of critical host defense inflammatory cytokines, including tumor necrosis factor (TNF). SIGNR3 signaling was dependent on an intracellular tyrosine-based motif and the tyrosine kinase Syk. Thus, the mouse DC-SIGN homologue SIGNR3 makes a unique contribution to protection of the host against a pulmonary bacterial pathogen.