RESUMEN
SecA2 is an ATPase present in some pathogenic Gram-positive bacteria, is required for translocation of a limited set of proteins across the cytosolic membrane, and plays an important role in virulence in several bacteria, including mycobacteria that cause diseases such as tuberculosis and leprosy. However, the mechanisms by which SecA2 affects virulence are incompletely understood. To investigate whether SecA2 modulates host immune responses in vivo, we studied Mycobacterium marinum infection in two different hosts: an established zebrafish model and a recently described mouse model. Here we show that M. marinum ΔsecA2 was attenuated for virulence in both host species and SecA2 was needed for normal granuloma numbers and for optimal tumor necrosis factor alpha response in both zebrafish and mice. M. marinum ΔsecA2 was more sensitive to SDS and had unique protrusions from its cell envelope when examined by cryo-electron tomography, suggesting that SecA2 is important for bacterial cell wall integrity. These results provide evidence that SecA2 induces granulomas and is required for bacterial modulation of the host response because it affects the mycobacterial cell envelope.
Asunto(s)
Adenosina Trifosfatasas/metabolismo , Proteínas Bacterianas/metabolismo , Granuloma/microbiología , Proteínas de Transporte de Membrana/metabolismo , Infecciones por Mycobacterium no Tuberculosas/microbiología , Mycobacterium marinum/metabolismo , Factor de Necrosis Tumoral alfa/metabolismo , Adenosina Trifosfatasas/genética , Animales , Proteínas Bacterianas/genética , Células Cultivadas , Femenino , Humanos , Inflamación/metabolismo , Macrófagos , Proteínas de Transporte de Membrana/genética , Ratones , Ratones Endogámicos C57BL , Infecciones por Mycobacterium no Tuberculosas/inmunología , Infecciones por Mycobacterium no Tuberculosas/metabolismo , Mycobacterium marinum/genética , Mycobacterium marinum/patogenicidad , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factor de Necrosis Tumoral alfa/genética , Virulencia , Pez CebraRESUMEN
Pathogenic mycobacteria, which cause multiple diseases including tuberculosis, secrete factors essential for disease via the ESX-1 protein export system and are partially protected from host defenses by their lipid-rich cell envelopes. These pathogenic features of mycobacterial biology are believed to act independently of each other. Key ESX-1 components include three ATPases, and EccA1 (Mycobacterium marinum MMAR_5443; M. tuberculosis Rv3868) is the least characterized. Here we show that M. marinum EccA1's ATPase activity is required for ESX-1-mediated protein secretion, and surprisingly for the optimal synthesis of mycolic acids, integral cell-envelope lipids. Increased mycolic acid synthesis defects, observed when an EccA1-ATPase mutant is expressed in an eccA1-null strain, correlate with decreased in vivo virulence and intracellular growth. These data suggest that two mycobacterial virulence hallmarks, ESX-1-dependent protein secretion and mycolic acid synthesis, are critically linked via EccA1.