Molecular characterization and biological effect of a C-type lectin receptor in Qihe crucian carp, Carassius auratus.

Abstract

C-type lectin receptors, as the important members of pattern-recognition receptors, play the crucial roles in the innate immune system, which discriminate self and non-self by recognizing and binding the carbohydrates on the surface of microorganism. In this study, we identified a C-type lectin receptor gene in Qihe crucian carp Carassius auratus (named as CaCLR). The full-length cDNA of CaCLR was composed of 1130 bp, with a 226 bp 5 -untranslated region (UTR), a 792 bp ORF encoding a 263aa protein, and a 112 bp 3 -UTR with a polyadenylation signal sequence AATAAA and a poly (A) tail. The predicted amino acid sequence of CaCLR is a single transmembrane receptor with a typical carbohydrate recognition domain (CRD) at its C-terminus. With regard to the mRNA transcript of CaCLR, it was ubiquitously detected in the tested tissues, among which it was the most abundant in head kidney. The temporal expressions of CaCLR were obviously up-regulated in liver, spleen, kidney, and head kidney after Aeromonas hydrophila and poly I: C challenge, respectively, and the patterns of expression changes were in a time-depended manner. The recombinant CaCLR (rCaCLR) purified from Escherichia coli BL21 (DE3), exhibited strong binding ability with lipopolysaccharide (LPS), peptidoglycan (PGN), β-Glucan, and Mannan, as well as five microorganisms including fungus (Saccharomyces cerevisiae), Gram-negative bacteria (A. hydrophila, E. coli and Vibrio anguillarum), and Gram-positive bacteria (Micrococcus lysodeikticus). In the presence of rCaCLR, the eliminating capacity against A. hydrophila could be enhanced in C. auratus. Taken together, CaCLR is involved in the antibacterial defense in C. auratus.