Immune recognition, antimicrobial and opsonic activities mediated by a sialic acid binding lectin from Ruditapes philippinarum

Abstract

In the present study, a sialic acid-binding lectin was identified and characterized from Manila clam Ruditapes philippinarum (designed as RpSABL-1). Multiple alignments strongly suggested that RpSABL-1 was a new member of the sialic acid-binding lectin family. In non-stimulated clams, RpSABL-1 transcripts were constitutively expressed in all five tested tissues, especially in hepatopancreas. After Vibrio anguillarum challenge, the expression of RpSABL-1 mRNA was significantly up-regulated at 6 h (P < 0.05), 12 h (P < 0.01) and 24 h (P < 0.01). Recombinant RpSABL-1 protein (rRpSABL-1) displayed apparent binding activities towards lipopolysaccharides (LPS) and peptidoglycan (PGN), but not to glucan or chitin in vitro. Coinciding with the PAMPs binding assay, rRpSABL-1 exhibited obvious agglutination activities against Gram-positive bacterium Staphyloccocus aureus, Gram-negative bacteria Escherichia coli, V. anguillarum and Vibrio harveyi. Meanwhile, rRpSABL-1 showed antibacterial activities against E. coli, and biofilm formation of E. coli could also be inhibited after incubated with rRpSABL-1. Moreover, the encapsulation, phagocytosis and chemotactic ability of hemocytes could be enhanced by rRpSABL-1. All these results suggested that RpSABL-1 could function as a pattern recognition receptor with versatile functions in the innate immune responses of R. philippinarum.

Extensive Tandem Duplication Events Drive the Expansion of the C1q-Domain-Containing Gene Family in Bivalves

“…Bivalve C1qDC proteins are expressed in different tissues [13] and, upon secretion in the extracellular environment, they might be released in the hemolymph [7], in the extrapallial fluid [21] or in the mucus that covers the gills [13], offering a first line of defense against invading microorganisms in different body districts. The recognition of MAMPs by bivalve C1qDC proteins, which is probably aided by additional humoral factors, promotes the agglutination of bacterial cells [15,22], also triggering the migration and phagocytic activity of hemocytes [22,23,24], which clearly indicate an opsin-like function for these important soluble PRRs.…”

Identification and Characterization of a Novel Lectin from the Clam Glycymeris yessoensis and Its Functional Characterization under Microbial Stimulation and Environmental Stress

“…Additionally, these values increased with corresponding increases of GYL concentration, suggesting that the binding activities of GYL towards these examined PAMPs exhibit dose-dependent effects ( Figure 5 a). A sialic-acid-binding lectin (SABL) from the manila clam Ruditapes philippinarum displayed apparent binding activity towards LPS and PGN, but not to glucan, and exhibited obvious agglutination activities against the Gram-positive bacterium Vibrio harveyi [ 50 ]. The CTL from the oyster Crassostrea gigas (designated as CgCLec-2) could bind various PAMPs, including LPS, mannan, and PGN.…”