A low-density lipoprotein receptor-related protein (LRP)-like molecule identified from Chlamys farreri participated in immune response against bacterial infection

Low-density lipoprotein receptor-related protein (LRP) is a group of important endocytic receptors contributing to binding ligands and maintaining internal environment. In the present study, an LRP-like molecule was identified from Zhikong scallop Chlamys farreri (CfLPR), and its mRNA expression profiles, tissue location, and immunology activities were analyzed to explore its possible function in the innate immune system. The ORF of CfLRP was of 1971 bp encoding a polypeptide of 656 amino acids with ten low-density lipoprotein-receptor YWTD (LY) domains and one scavenger receptor cysteine-rich (SRCR) domain. It shared similar structure with out-membrane domains of LRP family members in mammalian. The mRNA transcripts of CfLRP were dominantly expressed in hepatopancreas and mantle (P < 0.01), and its mRNA level in hemocytes was up-regulated (P < 0.01) significantly after the stimulations of lipopolysaccharides (LPS), peptidoglycan (PGN) and β-glucan. Western blotting assay using polyclonal antibody specific for CfLRP revealed that CfLRP was localized in the plasma. The recombinant protein of CfLRP (rCfLRP) could bind acetylated low density lipoprotein (Ac-LDL), metalloprotease SPF1 of Vibrio splendidus and mannan, but could not bind other typical PAMPs such as LPS, PGN, β-glucan and zymosan. Meanwhile, rCfLRP also exhibited strong bacteriostatic activity to Gram-negative bacteria Vibrio anguillarum and V. splendidus. These results indicated that CfLRP could serve as a receptor to recognize and eliminate the invading pathogens, which provided a new implication in the function of LRP-like molecules in invertebrate immunity.