The Cellular Isopeptidase T Deubiquitinating Enzyme Regulates Kaposi’s Sarcoma-Associated Herpesvirus K7 Degradation

CARD and TM of MAVS of black carp play the key role in its self-association and antiviral ability

Mitochondrial antiviral signaling protein (MAVS) is an adaptor protein of the innate immune system of higher vertebrate. In this paper, the transcription profile of black carp MAVS (bcMAVS) in host cells in response to spring viremia of carp virus (SVCV) and grass carp reovirus (GCRV) infection was identified. EPC cells expressing bcMAVS possessed obviously enhanced antiviral activity against both SVCV and GCRV. Immunofluorescence (IF) staining data demonstrated that bcMAVS molecules were redistributed and formed aggregates on the mitochondria of EPC cells after virus infection. Co-immunoprecipitation (co-IP) assay in HEK293T cells demonstrated that bcMAVS proteins bound to each other, which suggested that this fish protein owned self-association in vivo. IF assay identified that the transmembrane (TM) domain of bcMAVS was crucial for its mitochondrial localization. Co-IP assays among bcMAVS mutants demonstrated that both N-terminal caspase recruitment domain (CARD) and TM domain were indispensible for dimerization of bcMAVS. It was interesting that Truncated-bcMAVS possessed much enhanced interferon-inducing activity and antiviral ability than wild type bcMAVS, which only contains CARD and TM. All the data generated in this study support the idea that oligomerization of bcMAVS on mitochondrion is crucial for the antiviral ability of bcMAVS, which is depend on both CARD and TM domain of this fish MAVS orthologue.

IFNa of triploid hybrid of gold fish and allotetraploid is an antiviral cytokine against SVCV and GCRV

Triploid hybrid of gold fish (Carassius auratus red var., ♀, 2n = 100) and allotetroploid (♂, 2n = 100) displays much improved disease resistance than its parents. In this paper, one of the type I IFNs of triploid hybrid (3nIFNa) has been cloned and characterized. The full-length cDNA of 3nIFNa consists of 740 nucleotides and the predicted 3nIFNa protein contains 183 amino acids. The mRNA transcription of 3nIFNa was detected in all the selected tissues of triploid hybrid and was obviously enhanced after SVCV or GCRV infection. bcIFNa was detected in both whole cell lysate and supernatant media of HEK293T cells transfected with plasmids expressing bcIFNa. It is interesting that the pre-matured 3nIFNa is modified with N-linked glycosylation, which is located within the N-terminal signal peptide. EPC cells showed much-decreased cytopathic effect when treated with 3nIFNa-containing media or transfected with plasmid expressing 3nIFNa at 24 h before SVCV or GCRV infection; and the virus titers in these cells were much lower than those of the control EPC cells. All the above data support the conclusion that 3nIFNa is a secreted cytokine functioning in host innate immune response against virus invasion.

Molecular cloning and characterization of IKKε gene from black carp Mylopharyngodon piceus

IKKε is an IκB kinase functioning in NF-κB signal pathway in the innate immune system of higher vertebrates. To exploit the function of IKKε of black carp (bcIKKε) in its antiviral innate immunity, the IKKε gene has been cloned from the RNA isolated from the spleen of black carp. The full-length cDNA of bcIKKε is 2537 bp, which encodes the peptide of 723 amino acids. bcIKKε contains a S-Tkc domain, a PKc domain and a UBL-TBK1-like domain and bcIKKε shares the highest amino acid sequence similarity with that of grass carp. bcIKKε was constitutively transcribed in the selected tissues of black carp including gill, kidney, heart, intestine, liver, muscle, skin and spleen; and the mRNA level of bcIKKε in these tissues varied right after SVCV or GCRV infection. bcIKKε had been well expressed in HEK293T cells and western blot assay determined that this fish kinase was around 80 KDa. The immunofluorescence assay of both NH3T3 cells and EPC cells demonstrated that bcIKKε was located in the cytosolic part of the cell. Report assay result showed that overexpression of bcIKKε in EPC cells activated the expression of both zebrafish IFN and EPC IFN. All our data suggest that bcIKKε is a novel fish kinase functioning in the innate antiviral immune response of black carp.

Identification and characterization of IKKε gene from grass carp Ctenopharyngodon idella

IKKε is an IKK-related kinase implicated in antiviral immune response in higher vertebrates. To elucidate the function of IKKε in teleost fish, grass carp IKKε (gcIKKε) has been cloned and characterized in this paper. The full-length cDNA of gcIKKε is composed of 2529 nucleotides and encodes a polypeptide of 723 amino acids. The mRNA transcription of gcIKKε was constitutively detected in all the selected tissues and the gcIKKε mRNA level increased at 36 h after GCRV infection. Western blot data of both HEK293T cells and EPC cells demonstrated that gcIKKε was around 80 KDa; and immunofluorescence staining data of both NIH3T3 cells and EPC cells determined gcIKKε was a cytosolic protein. The mRNA level of gcIKKε in CIK cells was increased more than 150 times right after poly(I:C) treatment and PMA treatment triggered gcIKKε mRNA transcription in CIK cells more than 100 times. Over-expression of gcIKKε in EPC cells activated the promoter activity of both zebrafish IFN and fathead minnow IFN. gcIKKε mRNA transcription level in CIK cells was increased from 48 h post GCRV infection with different MOIs. All the data support the idea that gcIKKε is a novel teleost IκB kinase recruited in the IFN-mediated antiviral immunity of grass carp.