Identification, expression profile and analysis of the antimicrobial activity of collectin 11 (CL-11, CL-K1), a novel complement-associated pattern recognition molecule, in half-smooth tongue sole (Cynoglossus semilaevis).

Collectin 11 (CL-11, also known as collectin kidney-1, CL-K1), a new member of the vertebrate C-type lectin superfamily, plays an important role in innate immunity as a pattern recognition molecule of the lectin complement pathway. However, little is known about CL-11 in teleosts. In the present study, a CL-11 homolog was identified and characterized from half-smooth tongue sole (Cynoglossus semilaevis) (designated as CsCL-11). The full-length cDNA of CsCL-11 is 1220 bp long and includes a 5'untranslated region (5'-UTR) of 180 bp, a 3'-UTR of 218 bp and an open reading frame (ORF) of 819 bp encoding 273 amino acids. Multiple sequence alignment revealed that the deduced CsCL-11 protein has the typical modular architecture (EPN and WTD) conserved throughout vertebrates, suggesting a conserved function of CsCL-11. Tissue expression profile analysis by quantitative real-time PCR (qRT-PCR) showed CsCL-11 to be ubiquitously distributed in tissues and highly expressed in the ovary and liver. A pattern of significant upregulation of CsCL-11 expression was observed in the blood, spleen, head kidney and gill at 6 h, 12 h and 24 h after infection with Vibrio anguillarum, and western blotting showed that natural CsCL-11 protein levels in the blood were significantly increased after V. anguillarum infection. Moreover, by binding to various bacteria, recombinant CsCL-11 (rCsCL-11) expressed in HEK-293 T cells displayed strong antibacterial activity. Taken together, these results suggest that CsCL-11 is a unique C-type lectin that is likely involved in host defense against bacterial infection. To our knowledge, this is the first study on CL-11 in marine fish.

Identification and characterization of a novel human collectin CL-K1.

Collectins are a family of C-type lectins with two characteristic structures, collagen like domains and carbohydrate recognition domains. They recognize carbohydrate antigens on microorganisms and act as host-defense. Here we report the cloning and characterization of a novel collectin CL-K1. RT-PCR analyses showed CL-K1 mRNA is present in all organs. The deduced amino acid sequence and the data from immunostaining of CL-K1 cDNA expressing CHO cells revealed that CL-K1 is expressed as a secreted protein. CL-K1 is found in blood by immunoblotting and partial amino acid analyses. CL-K1 showed Ca(2+)-dependent sugar binding activity of fucose and weakly mannose but not N-acetyl-galactosamine, N-acetyl-glucosamine, or maltose, though mannose-binding lectin (MBL) containing similar amino acid motif. CL-K1 can recognize specially several bacterial saccharides due to specific sugar-binding character. Elucidation of the role of two ancestor collectins of CL-K1 and CL-L1 could lead to see the biological function of collectin family.

Characterization and expression sites of newly identified chicken collectins.

Collectins are members of the family of vertebrate C-type lectins. They have been found almost exclusively in mammals, with the exception of chicken MBL. Because of their important role in innate immunity, we sought to identify other collectins in chicken. Using the amino acid sequences of known collectins, the EST database was searched and related to the chicken genome. Three chicken collectins were found and designated chicken Collectin 1 (cCL-1), chicken Collectin 2 (cCL-2), and chicken Collectin 3 (cCL-3), which resemble the mammalian proteins Collectin Liver 1, Collectin 11 and Collectin Placenta 1, respectively. Additionally, a lectin was found which resembled Surfactant Protein A, but lacked the collagen domain. Therefore, it was named chicken Lung Lectin (cLL). Tissue distribution analysis showed cCL-1, cCL-2 and cCL-3 are expressed in a wide range of tissues throughout the digestive, the reproductive and the lymphatic system. Similar to SP-A, cLL is mainly localized in lung tissue. Phylogenetic analysis indicates that cCL-1, cCL-2 and cCL-3 represent new subgroups within the collectin family. The newly found collectins may have an important function in avian host defence. Elucidation of the role of these pattern-recognition molecules could lead to strategies that thwart infectious diseases in poultry, which could also be beneficial for public health.