NOD2 pathway activation by MDP or Mycobacterium tuberculosis infection involves the stable polyubiquitination of Rip2.
The Rip2 kinase contains a caspase recruitment domain and has been implicated in the activation of the transcriptional factor NF-kappaB downstream of Toll-like receptors, Nod-like receptors, and the T cell receptor. Although Rip2 has been linked to Nod signaling, how Nod-Rip2 proteins mediate NF-kappaB activation has remained unclear. We find Rip2 required for Nod2-mediated NF-kappaB activation and to a lesser extent mitogen-activated protein kinase activation. We demonstrate that Rip2 and IkappaB kinase-gamma become stably polyubiquitinated upon treatment of cells with the NOD2 ligand, muramyl dipeptide. We also demonstrate a requirement for the E2-conjugating enzyme Ubc13, the E3 ubiquitin ligase Traf6, and the ubiquitin-activated kinase Tak1 in Nod2-mediated NF-kappaB activation. Rip2 polyubiquitination is also stimulated when macrophages are infected with live Mycobacterium tuberculosis but not when infected with heat-killed bacteria. Consistent with our data linking Rip2 to NOD and not Toll-like receptor signaling, M. tuberculosis-induced Rip2 polyubiquitination appears MyD88-independent. Collectively, these data reveal that the NOD2 pathway is ubiquitin-regulated and that Rip2 employs a ubiquitin-dependent mechanism to achieve NF-kappaB activation.
Pubmed ID: 17947236 RIS Download
Acetylmuramyl-Alanyl-Isoglutamine | Adjuvants, Immunologic | Animals | Cells, Cultured | Enzyme Activation | Extracellular Signal-Regulated MAP Kinases | I-kappa B Kinase | MAP Kinase Kinase Kinases | Macrophages | Mice | Mice, Knockout | Mycobacterium tuberculosis | Myeloid Differentiation Factor 88 | NF-kappa B | Nod2 Signaling Adaptor Protein | Receptor-Interacting Protein Serine-Threonine Kinases | Signal Transduction | TNF Receptor-Associated Factor 6 | Toll-Like Receptors | Tuberculosis | Ubiquitin | Ubiquitin-Conjugating Enzymes | Ubiquitin-Protein Ligases | Ubiquitination