Coulombe, F. et al. Increased NOD2-mediated recognition of N-glycolyl muramyl dipeptide. J. Exp. Med. 206, 1709-1716

Department of Medicine, McGill University Health Centre, Montreal, Quebec H3G 1A4, Canada.
Journal of Experimental Medicine (Impact Factor: 12.52). 09/2009; 206(8):1709-16. DOI: 10.1084/jem.20081779
Source: PubMed


Peptidoglycan-derived muramyl dipeptide (MDP) activates innate immunity via the host sensor NOD2. Although MDP is N-acetylated in most bacteria, mycobacteria and related Actinomycetes convert their MDP to an N-glycolylated form through the action of N-acetyl muramic acid hydroxylase (NamH). We used a combination of bacterial genetics and synthetic chemistry to investigate whether N-glycolylation of MDP alters NOD2-mediated immunity. Upon infecting macrophages with 12 bacteria, tumor necrosis factor (TNF) alpha secretion was NOD2 dependent only with mycobacteria and other Actinomycetes (Nocardia and Rhodococcus). Disruption of namH in Mycobacterium smegmatis obrogated NOD2-mediated TNF secretion, which could be restored upon gene complementation. In mouse macrophages, N-glycolyl MDP was more potent than N-acetyl MDP at activating RIP2, nuclear factor kappaB, c-Jun N-terminal kinase, and proinflammatory cytokine secretion. In mice challenged intraperitoneally with live or killed mycobacteria, NOD2-dependent immune responses depended on the presence of bacterial namH. Finally, N-glycolyl MDP was more efficacious than N-acetyl MDP at inducing ovalbumin-specific T cell immunity in a model of adjuvancy. Our findings indicate that N-glycolyl MDP has a greater NOD2-stimulating activity than N-acetyl MDP, consistent with the historical observation attributing exceptional immunogenic activity to the mycobacterial cell wall.

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    • "PGNs, the main component in bacteria biofilm, consist of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) glycan strands cross-linked by short peptides (Vollmer, Blanot, & de Pedro, 2008). Intact polymeric PGN, soluble PGN and a variety of PGN monomeric forms, including N-acetyl-muramyl-L-Ala-D-Glu-mDAP (M-TriDAP), PGN-derived muramyl dipeptide (MDP), N-acetyl MDP and N-glycolyl MDP are used to study the molecular mechanisms involved in the induction and repression of intestinal inflammation (Coulombe et al., 2009). Using HEK293 cell lines with PGN isolated from the Bacillus anthracis strain, researchers have found that primary innate immune cells respond efficiently to polymeric PGN, but not to PGN monomers (Iyer & Coggeshall, 2011). "
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