Caspase activation and recruitment domain found in MDA5, second repeat
Caspase activation and recruitment domain (CARD) found in MDA5 (melanoma-differentiation-associated gene 5), second repeat. MDA5, also known as IFIH1, contains two N-terminal CARD domains and a C-terminal RNA helicase domain. MDA5 is a cytoplasmic DEAD box RNA helicase that plays an important role in host antiviral response by sensing incoming viral RNA. Upon activation, the signal is transferred to downstream pathways via the adaptor molecule IPS-1 (MAVS, VISA, CARDIF), leading to the induction of type I interferons. Although very similar in sequence, MDA5 recognizes different sets of viruses compared to RIG-I, a related RNA helicase. MDA5 associates with IPS-1 through a CARD-CARD interaction. 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.
Jiyao W et al.(2023). "The conserved domain database in 2023.",