Identification and functional analysis of NOD2 and its two splicing variants associated with a novel pattern of signal regulation in teleost fishes. (July 2021)

• Record Type: Journal Article
• Authors: Li, Yunkun; Jin, La; Xia, Puzhen; Sui, Weikai; Huang, Anqi; Bu, Guixian; Meng, Fengyan; Kong, Fanli; Cao, Xiaohan; Han, Xingfa; Yu, Guozhi; Pan, Xiaofu; Yang, Shiyong; Zheng, Chongquan; Zeng, Xianyin; Du, Xiaogang
• Is Part Of: Developmental and comparative immunology. Volume 120(2021)
• Publication Date: 2021-07
• Subjects: NOD2 -- Splicing variant -- NF-κB -- Teleost fishes; Immunology -- Periodicals; Developmental immunology -- Periodicals; 616.079
• DOI: 10.1016/j.dci.2021.104049
• Languages: English
• ISSNs: 0145-305X

Abstract

Abstract: The nucleotide-binding oligomerization domain 2 (NOD2) has been identified as an important sensor for microorganic invasion in both mammals and teleost fishes. In this study, two splicing variants of NOD2 (NOD2-v1 and NOD2-v2) were identified as truncating the functional domains of wild-type NOD2 in the teleost fish Schizothorax prenanti . NOD2-v1 included an intron sequence that terminated within the third leucine-rich repeat (LRR) domain, while NOD2-v2 incorporated an insertion of one and half intron sequences and truncated within the second caspase activation and recruitment domain (CARD). NOD2, NOD2-v1 and NOD2-v2 genes were ubiquitously expressed. All three genes positively responded to exposure of Aeromonas hydrophila and lipopolysaccharide stimulation in varying degrees. Using luciferase activity assays in HEK293T cells, our results revealed that NOD2 activated the NF-κB signal and recognized muramyl dipeptide (MDP). NOD2-v1 exhibited deficiency in the LRR domains and could not sense MDP, but maintained the ability to activate NF-κB and enhanced NOD2-mediated MDP recognition. Given the significant change to the functional structure, NOD2-v2 lost its capacity for NF-κB activation, but interestingly repressed NOD2-mediated MDP sensing and NF-κB activation, and even NOD2-v1-induced NF-κB activation. Altogether, our study reveals a novel pattern of signal regulation by splicing variants in teleost fishes. Highlights: Human-like NOD2 splicing variants were firstly identified in S. prenanti, named NOD2, NOD2-v1 and NOD2-v2. NOD2 and NOD2-v1 but NOD2-v2 can induce NF-κB activation. NOD2-v1 and NOD2-v2 lose the function of sensing specific ligand MDP. NOD2-v2 represses NOD2-mediated MDP sensing and NF-κB activation, and even NOD2-v1-induced NF-κB activation.