Structural Elucidation of Inter-CARD Interfaces involved in NOD2 Tandem CARD Association and RIP2 Recognition

Nucleotide-binding and oligomerization domain-containing protein 2 (NOD2) recognizes the muramyl dipeptide and activates the NF-kappa B signaling cascade following its interaction with receptor-interacting protein 2 (RIP2) via caspase recruitment domains (CARDs). The NOD2-RIP2 interaction is not understood well due to inadequate structural information. Using comparative modeling and multimicrosecond timescale molecular dynamics simulations, we have demonstrated the association of NOD2-CARDs (CARDa-CARDb) and their interaction with RIP2(CARD). Our results suggest that a negatively charged interface of NOD2(CARDa) and positively charged type-Ia interface of NOD2(CARDb) are crucial for CARDa-CARDb association and the type-Ia interface of NOD2(CARDa) and type-Ib interface of RIP2(CARD) predicted to be involved in 1:1 CARD-CARD interaction. Moreover, the direct interaction of NOD2(CARDb) with RIP2(CARD) signifies the importance of both CARDs of NOD2 in RIP2-mediated CARD-CARD interaction. Altogether, the structural results could help in understanding the underlying molecular details of the NOD2-RIP2 association in higher and lower eukaryotes.