Abstract
CD209, a transmembrane lectin belonging to the C-type lectin family, can recognize carbohydrates on the surface of host cells and invading pathogens, and play an important role in cell adhesion and migration, pathogen recognition and immune activation. Although well characterized in mammals, CD209 is still under-researched in fish. Here, we report a CD209-like gene, which was named SsCD209like, in black rockfish Sebastes schlegelii, and analyzed its structure features, expression patterns and ligand-binding activities. SsCD209like displays structural similarities to mammalian CD209s, with a cytosolic tail at N-terminus, a transmembrane region and an extracellular part containing a neck region and a CRD at C-terminus. The extracellular region and the neck region of SsCD209like can both form dimers, which is different with the tetramer in human homologue. This result demonstrates the multimerization of CD209 homologue in fish for the first time. The EPN motif, a functional motif participating in sugar binding and affinity determination, is conserved in the CRD of SsCD209like, which is consistent with the higher binding strength of this lectin to L-fucose, D-GlcNAc and D-mannose. The binding of SsCD209like to different bacteria strains and bacteria-derived pathogen associated molecular patterns (PAMPs) are also observed in a dose-dependent manner. Results in this study show the sequence and structure features of SsCD209like and demonstrate its binding properties as a pathogen recognition receptor, which promotes our understanding of CD209 homologues in fish and provides basis for more in-depth studies of this molecule in the future.