A basic investigation on evolution of CL-L1 in vertebrates and its bioactivities in black rockfish (Sebastes schlegelii)

Abstract

Collectins, which belong to C-type lectins, are pattern recognition molecules of the innate immune system exhibiting binding ability to carbohydrate structures on microorganisms. CL-L1, a member of the collectin family, participates in host defense via recognizing pathogen structures and modulating complement activation, and also plays roles in developmental processes. Although research progress obtained in mammals, comparative studies of CL-L1s outside mammals are still very limited so far. In this research, CL-L1s from a range of vertebrates were analyzed in gene synteny, phylogenetic relationship and protein features. It's revealed that CL-L1 is widely distributed and generally conserved in vertebrates. The gene locus of CL-L1 exists stably and protein modules, i.e. the N-terminal region, collagen-like region, neck region and CRD, are conserved in a series of vertebrates. But it's worth noting that some characteristic motifs, i.e. EPN and WND, which are important in binding carbohydrates, are partly or completely lost in the CRDs of CL-L1s in teleost species. The CL-L1 in a marine teleost, the black rockfish, designated as SsCL-L1, is analyzed next. SsCL-L1 has incomplete motifs in its CRD, but shows different binding affinities to a series of monosaccharide. SsCL-L1 can bind different bacteria with different intensities, and agglutinate bacteria in the presence of Ca2+. Sugar binding mechanism of SsCL-L1 needs further studies and results in this work will promote the understanding of CL-L1 evolution in vertebrates and facilitate knowledge of immunological roles of fish collectins.