ALBERT

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Fish & Shellfish Immunology, Volume 93〈/p〉 〈p〉Author(s): Rajamanthrilage Kasun Madusanka, Thanthrige Thiunuwan Priyathilaka, N.D. Janson, T.D.W. Kasthuriarachchi, Sumi Jung, M.D. Neranjan Tharuka, Jehee Lee〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Galectins are β-galactoside-binding lectins, which are involved in pattern recognition, cell adhesion, and stimulation of the host innate immune responses against microbial pathogens. In spite of several functional studies on different galectins isolated from vertebrates and invertebrates, this is the first report to present functional studies for galectin-8 from the marine teleost tissues. In the present study, we characterized galectin-8 homolog from black rockfish (〈em〉Sebastes schlegelii〈/em〉), in molecular and functional aspects. Rockfish galectin-8 (〈em〉SsGal8〈/em〉) was found to consist of a 969 bp long open reading frame (ORF), encoding a protein of 322 amino acids and the predicted molecular weight was 35.82 kDa. 〈em〉In silico〈/em〉 analysis of 〈em〉SsGal8〈/em〉 revealed the presence of two carbohydrate binding domains (CRDs), at both N and C-termini and a linker peptide of 40 amino acids, in between the two domains. As expected, the phylogenetic tree categorized 〈em〉SsGal8〈/em〉 as a tandem-repeat galectin, and ultimately positioned it in the sub-clade of fish galectin-8. rSsGal8 was able to strongly agglutinate fish erythrocytes and the inhibition of agglutination was successfully exhibited by lactose and 〈span〉d〈/span〉-galactose. Bacterial agglutination assay resulted in agglutination of both Gram (+) and Gram (−) bacteria, including 〈em〉Escherichia coli, Vibrio harveyi, Vibrio parahaemolyticus, Streptococcus parauberis, Lactococcus garvieae, Streptococcus iniae〈/em〉 and 〈em〉Vibrio tapetis.〈/em〉 The tissue distribution analysis based on qPCR assays, revealed a ubiquitous tissue expression of 〈em〉SsGal8〈/em〉 for the examined rockfish tissues, with the most pronounced expression in blood, followed by brain, intestine, head kidney and kidney. Furthermore, the mRNA transcription level of 〈em〉SsGal8〈/em〉 was significantly up-regulated in spleen, liver and head kidney, upon immune challenges with 〈em〉Streptococcus iniae〈/em〉, LPS and poly I:C, in a time dependent manner. Taken together, these findings strongly suggest the contribution of 〈em〉SsGal8〈/em〉 in regulating innate immune responses to protect the rockfish from bacterial infections.〈/p〉〈/div〉 〈/div〉