Caspase activation and recruitment domain of Receptor Interacting Protein 2
Caspase activation and recruitment domain (CARD) of Receptor Interacting Protein 2 (RIP2/RIPK2/RICK/CARDIAK/CARD3). RIP kinases serve as essential sensors of cellular stress. Vertebrates contain several types containing a homologous N-terminal kinase domain and varying C-terminal domains. RIP2 harbors a C-terminal CARD domain and functions as an effector kinase downstream of the pattern recognition receptors from the Nod-like (NLR)-family, NOD1 and NOD2, which recognizes bacterial peptidoglycans released upon infection. This cascade is implicated in inflammatory immune responses and the clearance of intracellular pathogens. RIP2 associates with NOD1 and NOD2 via CARD-CARD interactions. In general, CARDs are death domains (DDs) found associated with caspases. They are known to be important in the signaling pathways for apoptosis, inflammation, and host-defense mechanisms. DDs are protein-protein interaction domains found in a variety of domain architectures. Their common feature is that they form homodimers by self-association or heterodimers by associating with other members of the DD superfamily including PYRIN and DED (Death Effector Domain). They serve as adaptors in signaling pathways and can recruit other proteins into signaling complexes.