Isolation and characterization of two novel C-type lectins from the oriental river prawn, Macrobrachium nipponense

C-type lectins are a family of calcium-dependent carbohydrate-binding proteins which are believed to play important roles in the innate immunity of invertebrates. This study identified two novel C-type lectins, designated as MnCTLDcp2 and MnCTLDcp3, from the oriental river prawn Macrobrachium nipponense. The full-length cDNA of MnCTLDcp2 was of 1582 bp with an open reading frame (ORF) of 972 bp encoding a polypeptide of 323 amino acids. The complete nucleotide sequence of MnCTLDcp3 cDNA was 583 bp, containing a 555 bp ORF encoding a putative protein of 184 deduced amino acids. The deduced MnCTLDcp2 and MnCTLDcp3 proteins both contained a single C-type lectin-like domain (CTLD). Besides, MnCTLDcp2 contains a signal peptide and an low-density lipoprotein receptor class A (LDLa) domain. Reverse transcription PCR showed that MnCTLDcp2 was expressed in the heart, gill, nerve hepatopancreas and intestine; MnCTLDcp3 was expressed in the hepatopancreas, heart, nerve, gill and muscle. Their expression in the heart tissue was regulated following challenge with bacteria. The microbial agglutination assay showed that both MnCTLDcp2 and MnCTLDcp3 could agglutinated bacteria in the presence of calcium. All these results suggested that MnCTLDcp2 and MnCTLDcp3 functioned as pattern recognition receptors in the immune system of M. nipponense.