Proteomic identification and characterization of Ctenopharyngodon idella tumor necrosis factor receptor-associated protein 1 (CiTrap1): An anti-apoptosis factor upregulated by grass carp reovirus infection

• Translational level of CiTrap1 was upregulated 24 h in CIK cells post-GCRV infection.
• Transcriptional expression of CiTrap1 was upregulated following poly (I:C) stimulation and GCRV infection.
• Typical characteristics of apoptosis were observed in CIK cells infected with GCRV.
• Transcriptional levels of CiTrap1-interacting partners (PINK1 and Sorcin) were upregulated after GCRV infection.
• CiTrap1 might serve as an anti-apoptosis factor in antiviral immunity.

Human tumor necrosis factor receptor-associated protein 1 (Trap1) is a mitochondrial protein identical to heat shock protein 75 (HSP75) that plays an important role in protecting cells from oxidative stress and apoptosis. In this study, grass carp (Ctenopharyngodon idella) tumor necrosis factor receptor-associated protein 1 (designated as CiTrap1) was identified through two-dimensional electrophoresis (2-DE) analysis and its pattern of expression was investigated in grass carp kidney (CIK) cells infected with grass carp reovirus (GCRV). The full length cDNA of CiTrap1 contained an opening reading frame of 2157 bp that encoded a peptide of 718 amino acids. Phylogenetic analyses indicated that the CiTrap1 shared 87% identity with its homologue from zebrafish (Danio rerio). The transcriptional level of CiTrap1 in CIK cells was upregulated post virus infection as well as poly (I: C) stimulation. Following virus infection, grass carp PTEN-induced putative kinase 1 (PINK1) and Sorcin, whose coding proteins interact with Trap1 in human, were simultaneously upregulated with CiTrap1. Typical characteristics of apoptosis were observed in CIK cells infected with GCRV by DAPI staining, DNA ladder electrophoresis, TUNEL assay and Annexin Ⅴ labeling. RNAi-mediated silencing of CiTrap1 in CIK cells resulted in the increased rate of virus-induced apoptotic cells. The results of this study suggest that CiTrap1 is involved in the host's innate immune response to viral infection possibly through protecting infected cells from apoptosis.