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As a non-coding RNA with regulatory functions, microRNAs(miRNAs) can regulate gene expression and participate in a variety of physiological and pathological processes. In recent years, although there have been many studies on miRNA, the regulation mechanisms of miRNA in teleost fish have not been fully elucidated. In this study, it was first predicted that MITA is the target of miR-27c through bioinformatics, and it was confirmed by dual fluorescence experiments. Then we found that miR-27c can inhibit the expression of MITA at the mRNA and protein levels, thereby promoting the NF-κB or IRF3 pathway. It is speculated that miR-27c plays an important role in the innate immunity of teleost fish. This study will help to further understand miRNAs regulatory mechanism in teleost fish.

MyD88 is a typical street protein of the TLRs signaling pathway and is a central player in innate immune signaling, which can regulate the NF-κB signaling pathway and promote downstream inflammatory factors. However, studies on the molecular mechanisms of the MyD88-mediated NF-κB signaling pathway in teleosts have been poorly reported. In this study, we report that Zw10 targets MyD88 to inhibit NF-κB activation. Zw10 inhibits cell proliferation and MyD88-mediated innate immunity in fish. Zw10 interacts with MyD88, and its Δ2 domain is very critical for MyD88 degradation. In addition, we found that Zw10 degrade MyD88 by autophagy, thereby negatively regulating the MyD88-mediated NF-κB signaling pathway. This study not only enriches the research on the innate immunity of teleost fish, but also provides insights for the regulating mechanism for mammals.

microRNAs (miRNAs) are highly conserved, small non-coding endogenous molecule, and can participate in a variety of biological processes in organisms such as development, growth and immune response. Dual-Specificity Phosphatases (DUSPs) are enzymes that can remove phosphate groups from phosphatases. Research found that DUSP1 is an important molecule in the process of MAPK regulation. However, as a significant regulatory factor, the study of DUSP1 was very few in fish. Consequently, in this study, the regulatory role of miRNAs on DUSP1 has been verified through dual-luciferase reporter assay and western blotting analysis. Furethermore, we found that miR-375 mimics and pre-miR-375 plasmid can negatively regulate the target gene DUSP1 in miiuy croaker through combining with 3'untranslated region of DUSP1 gene. These experiment results directly indicate the negative regulatory function of miR-375 to DUSP1. Moreover, miR-375 can negatively regulate NF-κB signaling pathway via target to DUSP1. This study can increase our knowledge and help us to understand complexity of genomic and complex gene expression regulatory networks in teleost fish.

As the central link and executor of cell apoptosis, the caspase protease family has received extensive attention in recent years. However, the genetic characteristics and immune functions of some caspases are still unknown in fish. In our study, we cloned the full-length caspase-2 (mmCasp2) and caspase-8 (mmCasp2) of miiuy croaker, then we analyzed characteristics and functions of these two genes which are upstream of the apoptosis cascade reaction. Mmcasp2 and mmCasp8 exhibited a conserved domain (CASc), and the different part is that the mmCasp2 has a CARD domain, while mmCasp8 have two DED domains. Sequence and evolution analysis results showed that caspase-2 is more conservative than caspae-8 in the process of evolution. Cellular localization analysis showed that the distribution of mmCasp2 and mmCasp2 was in cytoplasm. The real-time PCR analysis showed that these two caspases are constitutively expressed in different tissues, and the expression of mmCasp2 and mmCasp8 were up-regulated in the liver, spleen, and kidney after infection with V. anguillarum. Lastly, qRT-PCR and Luciferase assays analysis showed that mmCasp2 and mmCasp8 can inhibit the NF-кB pathway. In general, we systematically analyzed the structure, evolution and related functional experiments of the caspase-2 and caspase-8 in miiuy croaker, which will help further understand the role caspase family plays in the apoptosis and immune response.

microRNAs (miRNAs), a crucial class of small non-coding RNA species, have been extensively studied as key molecular in immune regulation in the past decades. Here, we discover a new miRNA miR-148-1-5p and we elaborate that miR-148-1-5p functions as a negative regulator to participate in innate immune responses. In this article, it has been researched that the regulation effect of miR-148-1-5p to the nuclear factor kappaB (NF-κB) signaling pathway by targeting IRAK1 in miiuy croaker. First, through bioinformatics software to predict the potential targets of miR-148-1-5p, we found that IRAK1 had a base complementary region with indicated miRNA. Next, the dual-luciferase assays revealed that overexpression of miR-148-1-5p mimics and pre-miR-148 plasmid could significantly inhibit the luciferase activity of wild-type IRAK1-3′UTR. However, miR-148-1-5p inhibitors attenuated the inhibition caused by miR-148-1-5p. In addition, we also confirmed that miR-148-1-5p could suppress the expression of IRAK1 at mRNA level. Collectively, the regulations of miR-148-1-5p to NF-κB signaling pathways via targeting the IRAK1 gene was studied in miiuy croaker, which provided new information to enrich the immune regulation network of miRNA in teleost fish.

Innate immune response is an important response mechanism for the host to achieve self-protection, and it plays an important role in identifying pathogens and resisting pathogen invasion. Growing evidences have shown that microRNA functions as a crucial regulator involved in the host innate immune response. In this study, the regulations of miR-1388-5p to regulate NF-κB signaling pathways via targeting the IRAK1 gene was studied in miiuy croaker. First, through bioinformatics software prediction, we found that IRAK1 is the direct target of miR-1388-5p, and then the prediction results were verified by using dual-luciferase assays. Next, we found that both miR-1388-5p mimics and pre-miR-1388 plasmids inhibit IRAK1 expression by complementing the seed sequence in the 3'-untranslated region (3'-UTR) of IRAK1. Finally, we observed that miR-1388-5p could negatively regulate NF-κB pathways through targeting IRAK1. These results provide new insights into the function of miR-1388-5p in fish innate immunity, meanwhile enriching miRNA-mediated regulatory networks.