2-Transmembrane C-type lectin from oriental river prawn Macrobrachium nipponense participates in antibacterial immune response.

As a type of pattern-recognition proteins (PRRs), C-type lectins (CTLs) perform important functions in non-self recognition and clearance of pathogens in innate immunity. In this study, a unique 2-transmembrane CTL (designated as Mn-2TM-cLec) with a single carbohydrate recognition domain (CRD) was isolated from Macrobrachium nipponense. The full-length cDNA of Mn-2TM-cLec consisted of 3265 bp with an 837 bp open reading frame encoding a protein with 278 amino acids. Mn-2TM-cLec was ubiquitously distributed in various tissues of normal prawn, particularly in the hemocytes, hepatopancreas, and gills. The expression of Mn-2TM-cLec was significantly up-regulated in the gills and hepatopancreas after the prawns were challenged with Staphylococcus aureus and Vibrio parahaemolyticus. RNA interference knock-down of Mn-2TM-cLec gene decreased the transcription levels of three antimicrobial peptides (anti-lipopolysaccharide factor (ALF) 1, ALF2, and Crustin (Crus) 1) after V. parahaemolyticus infection. The recombinant CRD of Mn-2TM-cLec could bind lipopolysaccharide, peptidoglycans, and diverse bacterial strains and agglutinate S. aureus and V. parahaemolyticus in a Ca-dependent manner. In addition, the rCRD enhanced the clearance of V. parahaemolyticus injected in prawns. In summary, Mn-2TM-cLec might act as a PRR to participate in the prawn immune defense against pathogens through its antimicrobial activity.