CHARACTERIZATIONS AND FUNCTIONAL ANALYSIS OF TYPE I INTERFERON RECEPTOR (IFNR) IN ORANGE-SPOTTED GROUPER Epinephelus coioides

Grouper aquaculture was known as high economical species in aquaculture industry, raising interests among fish farmers. However, outbreak of diseases easily caused high death rate of grouper. In order to reduce death rate and increase grouper resistance to virus, mechanism of first line of defense against virus diseases in teleost fish through signaling of secreted cytokine (type I IFN) is studied. Previous result indicated up-regulation of gene expression level of grouper IFN and downstream Mx protein gene in response to virus infection. However, interaction of IFN to its receptor (IFNR) for signaling cascade function is unclear.

To investigate interaction between type I IFN to its receptor (IFNR), full length orange-spotted grouper IFNR1 was firstly cloned and identified. Phylogenetic analysis indicated osgIFNR1 shared high homology similarities with other teleosts. Relative expression of osgIFNR1 was determined using real-time qPCR in regards to interferon treatment using immune organ primary cell culture. Gene expression of osgIFNR1 and downstream osgMx which act as marker was seen up-regulated in 4 hours post-stimulation indicating involvement of transcriptional level responses. We further used GF-1 cell line to observe interaction between ligand and receptor and carried out luciferase assay to analyze promoter activation to mimic signaling from ligand to downstream effector. The present study revealed effect of IFNR1 through up-regulation of gene expression level during 4 hours of interferon (IFN) treatment and up-regulation of Mx promoter expression level as activation of IFN signaling. This study contributed different insights in analysis of orange-spotted grouper IFNR role in type I interferon system.