A galectin from roughskin sculpin, Trachidermus fasciatus: molecular cloning and characterization

Galectins are a family of β-galactoside-binding lectins, which have been proved to be involved in host-pathogen interactions by recognizing pathogen associated molecular patterns (PAMPs) on the surface of virus, bacteria, fungi and protozoa. In this study, a galactoside-binding lectin homolog was identified from roughskin sculpin Trachidermus fasciatus, named TfGal. The full-length of TfGal cDNA was 1016 bp with a 5' untranslated region (UTR) of 134 bp and a 3' UTR of 474 bp, and the open reading frame (ORF) is 408 bp. The deduced protein was composed of 135 amino acids, including a carbohydrate-recognition domain and a galactoside-type carbohydrate-binding motif H-NPR/W--E-R. The deduced amino acid sequence shared 58.52%-87.4% similarities with the galectins of the other fishes. Quantitative real-time PCR (qRT-PCR) analysis demonstrated that TfGal mRNA was abundantly expressed in the ovary, heart, stomach, skin, moderately expressed in the liver, brain, gills, spleen, and rarely expressed in the hemocytes, meat and intestine. The expression of TfGal mRNA in the hemocytes and the skin was dramatically up-regulated after challenged with LPS, reaching the highest level at 2 h post-challenge, and then dropped abruptly, while the expression of TfGal mRNA in the liver was up-regulated at 2-6 h post-challenge, and then returned to the normal level, with an increase at 96 h post-challenge again. However, no obvious change of the expression of TfGal mRNA was detected in the stomach. Recombinant TfGal purified from Escherichia coli (BL21) could agglutinate and/or bind microorganisms in Ca(2+)-independent manner. These results suggested that TfGal might be involved in the innate immune response of roughskin sculpin.