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

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

Research output: Contribution to journalJournal articleResearchpeer-review

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.
Original languageEnglish
JournalProceedings of the National Academy of Science of the United States of America
Volume96
Issue number19
Pages (from-to)10794-9
Number of pages5
ISSN0027-8424
Publication statusPublished - 1999

Keywords

  • Amino Acid Sequence
  • Cloning, Molecular
  • Glycoproteins
  • Humans
  • Intestine, Small
  • Islets of Langerhans
  • Lung
  • Macrophages, Alveolar
  • Models, Genetic
  • Molecular Sequence Data
  • Mucous Membrane
  • Opsonin Proteins
  • Proteolipids
  • Pulmonary Surfactant-Associated Protein D
  • Pulmonary Surfactant-Associated Proteins
  • Pulmonary Surfactants
  • Receptors, Immunologic
  • Reverse Transcriptase Polymerase Chain Reaction
  • Salivary Ducts
  • Sequence Homology, Amino Acid
  • Tissue Distribution

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