Molecular cloning and characterization of the lipopolysaccharide and β-1,3-glucan binding protein from oriental river prawn, Macrobrachium nipponense.

The lipopolysaccharide and β-1,3-glucan binding protein (LGBP), one of the pattern recognition proteins, plays an important role in the innate immune response of invertebrates. A 1,506 bp full-length cDNA of a LGBP gene was cloned and characterized from the oriental river prawn Macrobrachium nipponense (named as MnLGBP). Analysis of the nucleotide sequence revealed that the cDNA clone has an open reading frame of 1,119 bp, encoding a protein of 372 amino acids including a 21-aa signal peptide. The calculated molecular mass of the mature protein (351 aa) was 39.9 kDa with an estimated pI of 4.63. The MnLGBP sequence contains: (1) two putative integrin-binding motifs, (2) a glucanase motif, (3) two putative N-glycosylation sites, (4) one protein kinase C phosphorylation site, and (5) a putative recognition motif for β-1,3-linkage of polysaccharides. Sequence comparison based on the deduced amino acid sequence of MnLGBP showed varied identity of 89, 76 and 74% with those of Macrobrachium rosenbergii LGBP, Marsupenaeus japonicus β-1,3-glucan binding proteins, and Fenneropenaeus chinensis LGBP, respectively. Quantitative RT-PCR results showed that MnLGBP was expressed in nerve, intestine, muscle, gill, heart, haemocytes and at the highest level in hepatopancreas. After challenge with the pathogen, Aeromonas hydrophila and Vibrio parahaemolyticus, the expression of MnLGBP mRNA was significantly upregulated in the hepatopancreas compared to the control group. At the same time, the mRNA level of MnproPO increased dramatically at 48 h after injection of bacteria. These data should be helpful to better understand the function of MnLGBP in the prawn immune system.