CL-46, a Novel Collectin Highly Expressed in Bovine Thymus and Liver

Abstract

Collectins are oligomeric molecules with C-type lectin domains attached to collagen-like regions via α-helical neck regions. They bind nonself glycoconjugates on the surface of microorganisms and inhibit infection by direct neutralization, agglutination, or opsonization. During the characterization of the gene encoding bovine CL-43 (43-kDa collectin), we identified a novel collectin-gene. We report the cloning and partial characterization of the novel collectin CL-46. The mRNA comprises 1188 nucleotides encoding a protein of 371 aa with an included leader peptide of 20 residues. CL-46 has two cysteine residues in the N-terminal segment, a potential N-glycosylation site in the collagen region, and an extended hydrophilic loop close to the binding site of the carbohydrate recognition domain. It is expressed in the thymus, liver, mammary gland, and tissues of the digestive system. Recombinant CL-46 corresponding to the α-helical neck region and the C-type lectin domain binds preferential N-acetyl-d-glucoseamine and N-acetyl-d-mannoseamine. The gene encoding CL-46 spans ∼10 kb and consists of eight exons, with high structural resemblance to the gene encoding human surfactant protein D. It is located on the bovine chromosome 28 at position q1.8 together with the gene encoding conglutinin and CL-43. Several potential thymus-related cis-regulatory elements were identified in the 5′-upstream sequence, indicating that the expression in thymus may be modulated by signals involved in T cell development.

Collectin 11 (CL-11, CL-K1) Is a MASP-1/3–Associated Plasma Collectin with Microbial-Binding Activity

“…Polyclonal rabbitanti-human CL-11 Abs were raised against untagged human CL-11 expressed in CHO cells. Immunizations and protein G purification of Abs were performed as described previously (10). mAbs were produced by immunization of NMRI mice with recombinant human CL-11 as described previously (26).…”

“…Analyses of the specificity for mono-and disaccharides were carried out as previously described in detail (10). In brief, 96-well plates (Maxisorb; Nunc, Roskilde, Denmark) were coated with mannose-BSA (2 mg/ml; Dextra-laboratories, Reading, U.K.).…”

“…Collectins are part of the innate immune system and structurally defined by having a collagen-like region and C-type lectin domain, also referred to as a carbohydrate recognition domain (CRD) (1). At present, the group of collectins comprises mannan-binding lectin (MBL) (2), surfactant proteins A and D (SP-A and SP-D) (3,4), collectin liver 1 (CL-L1) (5,6), CL-P1 (7,8), conglutinin (9), CL-43 (9), and CL-46 (10). The latter three are limited to the species Bovidae (11), and collectin placenta 1 is a nonclassical collectin, which deviates in both the organization of domains and by being a transmembrane protein (8).…”

Characterization of the Oligomer Structure of Recombinant Human Mannan-binding Lectin

“…Surfactant protein A (36) forms a hexamer bouquetlike structure similar to C1q and MBL. Not much is known about the ultrastructure of the two most recently discovered collectins: liver collectin 1 (37) and CL-46 (38). It is believed that the N-terminal cysteines and their bonding patterns are responsible for the variation in the oligomer structures of the collectins.…”

Surfactant Protein D Gene Regulation

“…The potential importance of the four most upstream motifs is suggested by the spatial conservation of homologous sequences in the rat and mouse SP-D promoters (27,31) and/or in the promoter sequences of bovine conglutinin and CL-43, hepatic host defense collectins believed to have evolved from a primordial SP-D gene (32)(33)(34). A complete C/EBP motif nearly identical to the human sequence at Ϫ432 is found in the mouse gene (TTGaGAAA, reverse) (Fig.…”