Fig. 1
CARD domains from NOD1/2 and RIP2 are important for signaling. a Schematic overview of canonical RLR–MAVS, NOD1/2–RIP2, TLR–MyD88, and ASC signaling pathways. Adapters with CARD/pyrin domains relaying the activation signal from PRRs to their corresponding downstream effectors. The dashed arrow indicates previously proposed interactions between NOD1/2 and RIP2 via their CARD domains. b Illustrations of protein domain structure of human NOD1, NOD2, and RIP2. The CARD domains are highlighted in colors (light blue for NOD1–CARD, blue for NOD2–CARD, and orange for RIP2–CARD). c Sequence alignment of RIP2–CARD, NOD1–CARD, NOD2–CARDa, and NOD2–CARDb. Conserved residues are highlighted in orange and red colors. d, e NF-κB promoter activation by NOD1, NOD2, RIP2 proteins, and their CARD domains in HEK293T and HEK293T RIP2 KO cell lines. HEK293T cells were transfected with empty pflag vector or NOD1, NOD2, RIP2, RIP2–CARD, NOD1–CARD, and NOD2–CARD together with pGL4.32 NF-κB-RE vector, and CMV-Renilla vectors. The amount of plasmids that were transfected was calibrated with pFlag plasmids to ensure that the same amount of plasmids were used in each transfection. Cells were harvested 24 h post transfection and the level of NF-κB promoter activity was measured by dual luciferase assay according to the manufacturer’s instructions. Error bar represents standard deviation values of three independent repeats
