title: Analysis of fused-membrane structures in bronchoalveolar lavage fluid from patients with alveolar proteinosis.
abstract: Alveolar macrophages of patients with alveolar proteinosis, obtained by lung lavage, contain a large number of intracytoplasmic inclusions with mutlilamellar membranous structures, called fused-membrane structures, having a periodicity of 4.7 nm. To analyze the composition of these structures, we concentrated them from the bronchoalveolar lavage fluid of patients by a combination of sucrose density-gradient ultracentrifugation and enzyme hydrolysis using proteinase K. Fused-membrane structures were most numerous (26.2%) in a fraction obtained at the interface between 1.0 and 1.1 M sucrose solutions separated after proteinase K hydrolysis. This fraction was rich in acidic phospholipids. Hydrophobic surfactant apoproteins constituted about 77% of the proteins in this fraction, and a remarkable increase in the content of surfactant-associated protein C (SP-C) was found. The phospholipid-to-protein ratio was 0.25:1. Based on these results, we tried to reconstitute fused-membrane structures from purified lipids and hydrophobic proteins isolated from the patients' lavage fluid or from pig lungs. Only in the presence of both phospholipids and SP-C were similar multilamellar structures, having a periodicity of 4.3 to 4.5 nm, formed. These results suggest that fused-membrane structures have a close relationship to a hydrophobic surfactant-associated protein, SP-C, which accumulates in alveolar macrophages, possibly by incomplete digestion.
authors.affiliation: Department of Molecular Pathology, Kyoto University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Suzuki
authors.forename: H Q
authors.initials: HQ
authors.lastname: Shen
authors.forename: A
authors.initials: A
authors.lastname: Sato
authors.forename: S
authors.initials: S
authors.lastname: Nagai
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry / Q000166:cytology*; D002458:Cell Fractionation; D005260:Female; D006801:Humans; D002479:Inclusion Bodies / Q000737:chemistry / Q000648:ultrastructure; D016676:Macrophages, Alveolar / Q000737:chemistry / Q000648:ultrastructure; D008297:Male; D008561:Membrane Fusion; D008854:Microscopy, Electron; D008875:Middle Aged; D008969:Molecular Sequence Data; D010743:Phospholipids / Q000032:analysis; D011506:Proteins / Q000032:analysis / Q000235:genetics; D011510:Proteolipids / Q000032:analysis / Q000235:genetics; D011649:Pulmonary Alveolar Proteinosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D011663:Pulmonary Surfactants / Q000032:analysis / Q000235:genetics; D013552:Swine
chemical_list: D010743:Phospholipids; D011506:Proteins; D011510:Proteolipids; D011663:Pulmonary Surfactants