Abstract
NF-κB signaling is tightly regulated and essential to innate and adaptive immune responses, its regulatory mechanism remains unclear in various organisms, especially teleosts. In this study, we reported that IRF3 can negatively regulate TRIF-mediated NF-κB signaling pathway. Overexpression of IRF3 can inhibit TRIF-mediated NF-κB signaling pathway. However, knockdown of IRF3 had an opposite effect. IRF3 can promote the degradation of TRIF protein in mammal and fish cells, but this effect could be inhibited by MG132 treatment. Furthermore, we found that the inhibitory effect of IRF3 primary depended on its IRF association domain domain. IRF3 is crucial for the polyubiquitination and proteasomal degradation of TRIF. Our findings indicate that IRF3 negatively regulates TLR-mediated NF-κB signaling pathway by targeting TRIF for ubiquitination and degradation. This study provides a novel evidence on the negative regulation of innate immune signaling pathways in teleost fish and thus might provide new insights into the regulatory mechanisms in mammals.
Highlights
Vertebrates have evolved various immune defense systems to protect themselves against invading microorganisms and eliminate infective pathogens [1]
The innate immune system is the first line of host defense against pathogens, such as viruses and bacteria, and can recognize a limited, but highly conserved set of molecular structures known as pathogen-associated molecular patterns (PAMPs) [1]
To construct the expression plasmids, TRIF of the miiuy croaker was cloned into the Kpn I and BamH I sites of pEGFP-N1 and to the Kpn I and EcoR I sites of pCDNA3.1 (Invitrogen) with Flag tag; IRF3 of the miiuy croaker was cloned into the Kpn I and Xba I sites of pCDNA3.1 with myc tag; TBK1 of the miiuy croaker was cloned into the Hind III and EcoR I sites of pCDNA3.1 with HA tag; STAT1a of the miiuy croaker was cloned into the BamH I and EcoR I sites of pCDNA3.1 with myc tag; p65 of the miiuy croaker was cloned into the Hind III and Kpn I sites of pCDNA3.1 with Flag tag
Summary
Vertebrates have evolved various immune defense systems to protect themselves against invading microorganisms and eliminate infective pathogens [1]. The innate immune system is the first line of host defense against pathogens, such as viruses and bacteria, and can recognize a limited, but highly conserved set of molecular structures known as pathogen-associated molecular patterns (PAMPs) [1]. Aberrant immune responses occur, which leads to severe or even fatal bacterial sepsis, autoimmune, and chronic inflammatory diseases [7, 8]. These crucial signaling pathways have to be tightly regulated to maintain immune balance, which is essential to both innate and adaptive immunity
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