Molecular characterization and expression profiling of tandem-repeat galectin-8 from red-spotted grouper (Epinephelus akaara): Potential antibacterial, antiviral, and wound healing activities

Galectin-8 is a typical β-galactoside binding lectin, which primarily functions as a pattern recognition receptor and/or danger receptor that is engaged in pathogen recognition by the host innate immune system. Although several fish galectins have been identified, the role of galectin-8 in teleost immunity is still not fully understood. In this study, molecular, transcriptional, and immune-related functions of galectin-8 (EaGal8) from red-spotted grouper (Epinephelus akaara) were analyzed. The open reading frame of EaGal8 comprised 960 bp encoding 319 amino acids of a ∼35 kDa protein, composed of the N- and C-terminal carbohydrate recognition domains joined by a short hinge peptide. Phylogenetic analysis revealed that EaGal8 was closely related to the Epinephelus lanceolatus galectin-8-like protein. Although EaGal8 showed ubiquitous tissue expression, the highest expression level was observed in the blood. Immunostimulants, including lipopolysaccharide, poly(I:C), and nervous necrosis virus, significantly upregulated the EaGal8 transcription level in a time-dependent manner (p < 0.05). Furthermore, recombinant EaGal8 (rEaGal8) showed a binding affinity toward seven different carbohydrates in a concentration-dependent manner. In addition, rEaGal8 caused strong agglutination of fish red blood cells and several gram-positive and gram-negative bacteria, including Streptococcus iniae, Streptococcus parauberis, Lactococcus garvieae, Escherichia coli, Edwardsiella tarda, Vibrio alginolyticus, Vibrio parahaemolyticus, and Pseudomonas aeruginosa. For the first time in teleosts, we report the wound healing ability of galectin-8 in this study. At low concentrations, rEaGal8 showed potential wound healing responses in FHM cells, in vitro. Thus, this study reinforces the role of EaGal8 in innate immune responses against bacterial and viral infections and wound healing in red-spotted grouper.