Identification and characterization of the melanoma differentiation – associated gene 5 in sea perch, Lateolabrax japonicus. (August 2016) - Jia, Peng
Abstract: The RIG-I-like receptors family is a group of cytosolic RNA helicase proteins that can recognize viral RNA via binding to pathogen associated molecular pattern motifs within RNA ligands. A novel vertebrate RLR counterpart named LjMDA5 was firstly identified from the marine fish sea perch Lateolabrax japonicus in this study. The full-length cDNA of LjMDA5 is 3750 bp and encodes a polypeptide of 988 amino acids, containing two N-terminal tandem caspase activation and recruitment domains, a DExH (Asp-Glu-X-His) box domain, an HELICc domain, and a C-terminal domain RIG-I. Phylogenetic analysis showed that LjMDA5 shared the closest genetic relationship with the MDA5 of Larimichthys crocea. Quantitative RT-PCR analysis showed that LjMDA5 was ubiquitously expressed and up-regulated significantly in all selected tissues in vivo post NNV infection. Time course analysis showed that LjMDA5 transcripts significantly increased in spleen and kidney. We found LjMDA5 could be regulated in the sea perch LJB and LJF cell lines after lipopolysaccharide, polyinosinic-polycytidylic acid treatment and NNV challenge. RNA interference experiment indicated that silencing of LjMDA5 significantly increased RGNNV replication and virus production in NNV infected LJF cells. Our results revealed that MDA5 was essential for host defense against NNV, which provided new insights into the function of RLR signaling pathway during NNV infection in fish. Highlights: The first MDA5 was identified from sea perch. LjMDA5 transcripts were constitutively expressed in all examined tissues. LjMDA5 transcripts were induced greatly in immune and non-immune organs post NNV infection in vivo. LjMDA5 involved in response to LPS and poly(I:C) stimulation and NNV infection in vitro. Silencing of LjMDA5 by RNAi benefited the replication and virus production of RGNNV in vitro.