Mycobacterium tuberculosis protein ESAT-6 is a potent activator of the NLRP3/ASC inflammasome.
Interleukin-1beta (IL-1beta) represents one of the most important mediators of inflammation and host responses to infection. Mycobacterium tuberculosis (Mtb), the causative agent of human tuberculosis, induces IL-1beta secretion at the site of infection, but the underlying mechanism(s) are poorly understood. In this work we show that Mtb infection of macrophages stimulates caspase-1 activity and promotes the secretion of IL-1beta. This stimulation requires live intracellular bacteria expressing a functional ESX-1 secretion system. ESAT-6, an ESX-1 substrate implicated in membrane damage, is both necessary and sufficient for caspase-1 activation and IL-1beta secretion. ESAT-6 promotes the access of other immunostimulatory agents such as AG85 into the macrophage cytosol, indicating that this protein may contribute to caspase-1 activation largely by perturbing host cell membranes. Using a high-throughput shRNA-based screen we found that numerous NOD-like receptors (NLRs) and CARD domain-containing proteins (CARDs) were important for IL-1beta secretion upon Mtb infection. Most importantly, NLRP3, ASC and caspase-1 form an infection-inducible inflammasome complex that is essential for IL-1beta secretion. In summary, we show that recognition of Mtb infection by the NLRP3 inflammasome requires the activity of the bacterial virulence factor ESAT-6, and the subsequent IL-1beta response is regulated by a number of NLR/CARD proteins.
Centro de Patogénese Molecular, Faculdade de Farmácia, Universidade de Lisboa, Lisboa, Portugal.
Bibhuti B
BB
Mishra
Pedro
P
Moura-Alves
Avinash
A
Sonawane
Nir
N
Hacohen
Gareth
G
Griffiths
Luis F
LF
Moita
Elsa
E
Anes
D000942:Antigens, Bacterial / Q000276:immunology / Q000378:metabolism*; D001426:Bacterial Proteins / Q000276:immunology / Q000378:metabolism*; D053468:CARD Signaling Adaptor Proteins; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000276:immunology; D020170:Caspase 1 / Q000096:biosynthesis; D003598:Cytoskeletal Proteins / Q000096:biosynthesis* / Q000276:immunology; D054884:Host-Pathogen Interactions; D006801:Humans; D053583:Interleukin-1beta / Q000378:metabolism*; D008264:Macrophages / Q000276:immunology / Q000382:microbiology*; D009169:Mycobacterium tuberculosis / Q000276:immunology* / Q000472:pathogenicity; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D053468:CARD Signaling Adaptor Proteins; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; C093276:ESAT-6 protein, Mycobacterium tuberculosis; D053583:Interleukin-1beta; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; C402202:PYCARD protein, human; D020170:Caspase 1