RESUMO
Bacterial cell wall muramyl dipeptide (MDP) and glucosaminyl-MDP (GMDP) are potent activators of innate immunity. Two receptor targets, NOD2 and YB1, have been reported; we investigated potential overlap of NOD2 and YB1 pathways. Separate knockdown of NOD2 and YB1 demonstrates that both contribute to GMDP induction of NF-κB expression, a marker of innate immunity, although excess YB1 led to induction in the absence of NOD2. YB1 and NOD2 co-migrated on sucrose gradient centrifugation, and GMDP addition led to the formation of higher molecular mass complexes containing both YB1 and NOD2. Co-immunoprecipitation demonstrated a direct interaction between YB1 and NOD2, a major recombinant fragment of NOD2 (NACHT-LRR) bound to YB1, and complex formation was stimulated by GMDP. We also report subcellular colocalization of NOD2 and YB1. Although YB1 may have other binding partners in addition to NOD2, maximal innate immunity activation by muramyl peptides is mediated via an interaction between YB1 and NOD2.
Assuntos
Acetilmuramil-Alanil-Isoglutamina/análogos & derivados , Acetilmuramil-Alanil-Isoglutamina/imunologia , Monócitos/imunologia , Proteína Adaptadora de Sinalização NOD2/metabolismo , Proteína 1 de Ligação a Y-Box/metabolismo , Animais , Linhagem Celular , Imunidade Inata , Camundongos , NF-kappa B/metabolismo , Proteína Adaptadora de Sinalização NOD2/genética , Ligação Proteica , Multimerização Proteica/genética , Transporte Proteico , RNA Interferente Pequeno/genética , Ativação Transcricional/genética , Proteína 1 de Ligação a Y-Box/genéticaRESUMO
Disaccharide containing unit of peptidoglycan from bacterial cell wall, N-acetyl-d-glucosaminyl-N-acetylmuramyl-l-alanyl-d-glutaminamide (gluÑosaminyl-muramyl-dipeptide) registered in Russia as an immunomodulatory drug, is shown to participate in slow equilibrium of α and ß anomeric forms. Data of NMR spectra and molecular dynamics indicate that the α-anomer predominantly acquires a folded conformation stabilized by intramolecular hydrogen bond between the alanyl carbonyl and muramyl NH proton. The ß-form displays a considerable fraction of extended, non-hydrogen bonded structures. In the standard immunoadjuvant test system, the α-form is practically inactive, and the activity of the equilibrium mixture with α : ß = 68 : 32 ratio is due to the presence of ß-anomer. Such unique α-ß selectivity of biological action must be considered at the design of related immunoactive glycopeptides.