Molecular cloning and functional analysis of common carp (Cyprinus carpio) integrin α6 and the correlation with the resistance to CyHV-3 infection

Abstract

Integrin α6 (ITGα6) is involved in a variety of cellular physiological responses and plays an important role in the immune response. Currently, common carp is severely affected by the virus of Cyprinid herpesvirus 3 (CyHV-3) in aquaculture. Studies have shown that ITGα6 is associated with herpesvirus infection. However, the role of ITGα6 in the response to CyHV-3 virus infection is still unclear. In this paper, we cloned the ITGα6 from common carp (CcITGα6) and studied its expression profile after infection with CyHV-3. Two transcripts of CcITGα6 were cloned, named CcITGα6a and CcITGα6b. The full-length cDNA of the CcITGα6a transcript was 3867 bp, the ORF was 3273 bp, and 1090 amino acids were encoded. The full-length cDNA of the CcITGα6b transcript was 3368 bp, the ORF was 3189 bp, and 1062 amino acids were encoded. Two transcripts of CcITGα6 consist of four parts: the signal peptide, extracellular region, transmembrane region, and cytoplasmic region. The difference between the two CcITGα6 transcripts lies in the cytoplasmic region and no homologous sequence. Similarly, the secondary structure, glycosylation sites, and phosphorylation sites were different in the cytoplasmic region. Phylogenetic analysis showed that CcITGα6 was highly conserved and clustered with zebrafish ITGα6b. The two CcITGα6 transcripts were constitutively expressed in ten sample tissues but displayed distinct expression patterns. The highest relative expression levels of the two transcripts of CcITGα6 were observed in the head kidney, whereas the lowest was observed in the heart. The relative expression levels of the CcITGα6b transcript in the five tissues were significantly higher than the relative expression levels of the CcITGα6a transcript (p < 0.05), and they were significantly lower in the brain (p < 0.05). After CyHV-3 infection, the relative expression levels of two transcripts of CcITGα6 were higher in the breeding strain than in the non-breeding strain and reached the highest at 48 h and the lowest at 144 h. However, the expression of CcITGα6b in the breeding strain was significantly higher than the expression of CcITGα6b in the non-breeding strain at all infection stages (p < 0.05). This result indicated that CcITGα6b might play an important role in resistance to CyHV-3 in common carp, which provides a theoretical basis for the study of the CyHV-3 resistance mechanism of common carp and lays the foundation for guiding breeding.