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Cloning of gp-340, a putative opsonin receptor for lung surfactant protein D.

ABSTRACT: Surfactant protein D (SP-D) is an oligomeric C type lectin that promotes phagocytosis by binding to microbial surface carbohydrates. A 340-kDa glycoprotein (gp-340) has been shown to bind SP-D in the presence of calcium but does so independently of carbohydrate recognition. This protein exists both in a soluble form and in association with the membranes of alveolar macrophages. The primary structure of gp-340 has been established by molecular cloning, which yielded a 7,686-bp cDNA sequence encoding a polypeptide chain of 2, 413 amino acids. The domain organization features 13 scavenger receptor cysteine-rich (SRCR) domains, each separated by an SRCR-interspersed domain, except for SRCRs 4 and 5, which are contiguous. The 13 SRCR domains are followed by two C1r/C1s Uegf Bmp1 domains separated by a 14th SRCR domain and a zona pellucida domain. gp-340 seems to be an alternative spliced form of DMBT1. Reverse transcription-PCR analysis showed that the main sites of synthesis of gp-340 are lung, trachea, salivary gland, small intestine, and stomach. Immunohistochemistry revealed strong staining for gp-340 in alveolar and other tissue macrophages. Immunostaining of the macrophage membrane was either uniform or focal in a way that suggested capping, whereas other macrophages showed strong intracellular staining within the phagosome/phagolysosome compartments. In some macrophages, SP-D and gp-340 were located in the same cellular compartment. Immunoreactive gp-340 was also found in epithelial cells of the small intestine and in the ducts of salivary glands. The distribution of gp-340 in macrophages is compatible with a role as an opsonin receptor for SP-D.

SUBMITTER: Holmskov U

PROVIDER: S-EPMC17962 | biostudies-literature | 1999 Sep

REPOSITORIES: biostudies-literature

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Cloning of gp-340, a putative opsonin receptor for lung surfactant protein D.

Holmskov U U Mollenhauer J J Madsen J J Vitved L L Gronlund J J Tornoe I I Kliem A A Reid K B KB Poustka A A Skjodt K K

Proceedings of the National Academy of Sciences of the United States of America 19990901 19

Surfactant protein D (SP-D) is an oligomeric C type lectin that promotes phagocytosis by binding to microbial surface carbohydrates. A 340-kDa glycoprotein (gp-340) has been shown to bind SP-D in the presence of calcium but does so independently of carbohydrate recognition. This protein exists both in a soluble form and in association with the membranes of alveolar macrophages. The primary structure of gp-340 has been established by molecular cloning, which yielded a 7,686-bp cDNA sequence encod ...[more]

PMID: 10485905

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Project description:Human pulmonary surfactant protein D (SP-D) was identified in lung lavage by its similarity to rat SP-D in both its molecular mass and its Ca(2+)-dependent-binding affinity for maltose [Persson, Chang & Crouch (1990) J. Biol. Chem. 265, 5755-5760]. For structural studies, human SP-D was isolated from amniotic fluid by affinity chromatography on maltose-Sepharose followed by f.p.l.c. on Superose 6, which showed it to have a molecular mass of approx. 620 kDa in non-dissociating conditions. On SDS/PAGE the human SP-D behaved as a single band of 150 kDa or 43 kDa in non-reducing or reducing conditions respectively. The presence of a high concentration of glycine (22%), hydroxyproline and hydroxylysine in the amino acid composition of human SP-D indicated that it contained collagen-like structure. Collagenase digestion yielded a 20 kDa collagenase-resistant globular fragment which retained affinity for maltose. Use of maltosyl-BSA as a neoglycoprotein ligand in a solid-phase binding assay showed that human SP-D has a similar carbohydrate-binding specificity to rat SP-D, but a clearly distinct specificity from that of other lectins, such as conglutinin, for a range of simple saccharides. Amino acid sequence analysis established the presence of collagen-like Gly-Xaa-Yaa triplets in human SP-D and also provided sequence data from the globular region of the molecule which was used in the synthesis of oligonucleotide probes. Screening of a human lung cDNA library with the oligonucleotide probes, and also with rabbit anti-(human SP-D), allowed the isolation of two cDNA clones which overlap to give the full coding sequence of human SP-D. The derived amino acid sequence indicates that the mature human SP-D polypeptide chain is 355 residues long, having a short non-collagen-like N-terminal section of 25 residues, followed by a collagen-like region of 177 residues and a C-terminal C-type lectin domain of 153 residues. Comparison of the human SP-D and bovine serum conglutinin amino acid sequences indicated that they showed 66% identity despite their marked differences in carbohydrate specificity.

Dataset Information

Cloning of gp-340, a putative opsonin receptor for lung surfactant protein D.

Publications

Cloning of gp-340, a putative opsonin receptor for lung surfactant protein D.

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