Int. J. Mol. Sci. 2017, 18(6), 1147; doi:10.3390/ijms18061147
Mutual Regulation of NOD2 and RIG-I in Zebrafish Provides Insights into the Coordination between Innate Antibacterial and Antiviral Signaling Pathways
1
Laboratory of Biochemistry and Molecular Biology, School of Marine Sciences, Ningbo University, Ningbo 315211, China
2
College of Life Sciences, Zhejiang University, Hangzhou 310058, China
3
Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China
*
Authors to whom correspondence should be addressed.
Academic Editor: Li Lin
Received: 1 April 2017 / Revised: 15 May 2017 / Accepted: 23 May 2017 / Published: 27 May 2017
(This article belongs to the Section Biochemistry, Molecular and Cellular Biology)
Abstract
Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) and retinoic acid-inducible gene I (RIG-I) are two important cytosolic pattern recognition receptors (PRRs) in the recognition of pathogen-associated molecular patterns (PAMPs), initiating innate antibacterial and antiviral signaling pathways. However, the relationship between these PRRs, especially in teleost fish models, is rarely reported. In this article, we describe the mutual regulation of zebrafish NOD2 (DrNOD2) and RIG-I (DrRIG-I) in innate immune responses. Luciferase assays were conducted to determine the activation of NF-κB and interferon signaling. Morpholino-mediated knockdown and mRNA-mediated rescue were performed to further confirm the regulatory roles between DrNOD2 and DrRIG-I. Results showed that DrNOD2 and DrRIG-I shared conserved structural hallmarks with their mammalian counterparts, and activated DrRIG-I signaling can induce DrNOD2 production. Surprisingly, DrNOD2-initiated signaling can also induce DrRIG-I expression, indicating that a mutual regulatory mechanism may exist between them. Studies conducted using HEK293T cells and zebrafish embryos showed that DrRIG-I could negatively regulate DrNOD2-activated NF-κB signaling, and DrNOD2 could inhibit DrRIG-I-induced IFN signaling. Moreover, knocking down DrRIG-I expression by morpholino could enhance DrNOD2-initiated NF-κB activation, and vice versa, which could be rescued by their corresponding mRNAs. Results revealed a mutual feedback regulatory mechanism underlying NOD2 and RIG-I signaling pathways in teleosts. This mechanism reflects the coordination between cytosolic antibacterial and antiviral PRRs in the complex network of innate immunity. View Full-TextKeywords:
zebrafish NOD2; zebrafish RIG-I; NF-κB signaling; IFN signaling; negative mutual regulation
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Nie, L.; Xu, X.-X.; Xiang, L.-X.; Shao, J.-Z.; Chen, J. Mutual Regulation of NOD2 and RIG-I in Zebrafish Provides Insights into the Coordination between Innate Antibacterial and Antiviral Signaling Pathways. Int. J. Mol. Sci. 2017, 18, 1147.
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