Pattern recognition receptor (PRR) that detects bacterial peptidoglycan fragments and other danger signals and plays an important role in gastrointestinal immunity (PubMed:12527755). Upon stimulation by muramyl dipeptide (MDP), a fragment of bacterial peptidoglycan, binds the proximal adapter receptor-interacting RIPK2, which recruits ubiquitin ligases as XIAP, BIRC2, BIRC3, INAVA and the LUBAC complex, triggering activation of MAP kinases and activation of NF-kappa-B signaling (PubMed:11087742, PubMed:21887730). This in turn leads to the transcriptional activation of hundreds of genes involved in immune response. Required for MDP-induced NLRP1-dependent CASP1 activation and IL1B release in macrophages (PubMed:18511561). Component of an autophagy-mediated antibacterial pathway together with ATG16L1 (PubMed:20637199). Also plays a role in sensing single-stranded RNA (ssRNA) from viruses. Interacts with mitochondrial antiviral signaling/MAVS, leading to activation of interferon regulatory factor-3/IRF3 and expression of type I interferon (PubMed:19701189). Besides recognizing pathogens, participates in surveillance of cellular homeostasis through sensing and binding to the cytosolic metabolite sphingosine-1-phosphate and then initating inflammation process (PubMed:33942347). Component of a signaling complex consisting of ARHGEF2, NOD2 and RIPK2 (PubMed:11087742, PubMed:21887730). Interacts (via CARD domain) with RIPK2 (via CARD domain) (PubMed:19592251, PubMed:21887730, PubMed:27812135). Interacts with ATG16L1 (PubMed:20637199, PubMed:23376921). Interacts (via NACHT domain) with CARD9 (PubMed:24960071). Interacts with ANKRD17 (via N-terminus) (PubMed:23711367). Interacts with HSPA1A; the interaction enhances NOD2 stability (PubMed:24790089). Interacts (via both CARD domains) with HSP90; the interaction enhances NOD2 stability (PubMed:23019338). Interacts (via CARD domain) with SOCS3; the interaction promotes NOD2 degradation (PubMed:23019338). Interacts (via CARD domain) with ERBBI2P; the interaction inhibits activation of NOD2 (PubMed:16203728). Interacts (via CARD domain) with CASP1; this interaction leads to IL1B processing. Also interacts with CASP4. Interacts with NLRP1; this interaction is enhanced in the presence of muramyl dipeptide (MDP) and leads to increased IL1B release (PubMed:18511561). Interacts with MAPKBP1; the interaction is enhanced in the presence of muramyl dipeptide (MDP) (PubMed:22700971). Interacts with INAVA; the interaction takes place upon PRR stimulation (PubMed:28436939). Interacts with ANKHD1, C10ORF67, CHMP5, DOCK7, ENTR1, KRT15, LDOC1, PPP1R12C, PPP2R3B, TRIM41 and VIM (PubMed:27812135). Interacts with NLRP12; this interaction promotes degradation of NOD2 through the ubiquitin-proteasome pathway (PubMed:30559449). Mainly expressed in monocytes (PubMed:11087742). Expressed also in intestinal mucosa, mainly in Paneth cells and, at lower extent, in the glandular epithelium (PubMed:22700971). Up-regulated by muramyl-dipeptide and lipopolysaccharide. The ATG16L1-binding motif mediates interaction with ATG16L1. Intramolecular interactions between the N-terminal moiety and the leucine-rich repeats (LRR) may be important for autoinhibition in the absence of activating signal. In the absence of LRRs, the protein becomes a constitutive activator of CASP1 cleavage and proIL1B processing. Palmitoylated. Palmitoylation is required for proper recruitment to the bacterial entry site and hence for proper signaling upon cognate peptidoglycan detection. Polyubiquitinated following MDP stimulation, leading to proteasome-mediated degradation (PubMed:23019338). The disease is caused by variants affecting the gene represented in this entry. Disease susceptibility is associated with variants affecting the gene represented in this entry. Disease susceptibility is associated with variants affecting the gene represented in this entry. Can activate NF-kappa-B. More abundant. Can activate NF-kappa-B. Can activate NF-kappa-B. Repertory of FMF and hereditary autoinflammatory disorders mutations