A Novel C-type Lectin From Eriocheir Sinensis Functions As A Pattern Recognition Receptor With Antibacterial Activity

C-type lectins as one of pattern recognition receptors play great roles in recognizing and eliminating pathogens in innate immunity.In this study, a novel C-type lectin (EsLecD) was identified from Eriocheir sinensis. The cloning of full-length EsLeD cDNA were based on the initial expressed sequence tags (EST) isolated from a hepatopancreatic cDNA library.The full-length cDNA of EsLecD was686bp with an open reading frame of468bp encoding a putative protein of155amino acids with a N-terminal signal peptide and a single carbohydrate-recognition domain (CRD). The mRNA transcripts of EsLecD was mainly detected in hepatopancreas but not in other tissues by Reverse transcription-PCR analysis and post LPS immune challenge, the mRNA expression level in hemocytes significantly up-regulated. The recombinant EsLecD(rEsLecD) protein can bind to some Gram-positive, Gram-negative bacteria and Yeast and Calcium (Ca2+) can increase the binding activity, but not essential. rEslecD may bind to pathogen with a wide range. The recombinant protein can inhibit the grouth of the microorganism we tested at absent of Ca2+. Our results showed rEsLecD agglutinated some microorganism in a Ca2+-dependent manner. Except for the binding activities, rEsLecD could induce the aggregation but does not happen in the absence of Ca2+. It has been shown that the rEsLecD could also stimulate hemocyte encapsulation. In conclusion, our study suggested that rEsLecD as a significant PRR have a part in recognizing invading pathogens in crabs and play a great role in innate immunity.