Surfactant protein D (SP-D) counteracts the inhibitory effect of surfactant protein A (SP-A) on phospholipid secretion by alveolar type II cells. Interaction of native SP-D with SP-A.
The surfactant proteins SP-A and SP-D were obtained from rats given intratracheal instillation of silica. SP-D was isolated from the 33,000 g supernatant of rat bronchoalveolar lavage fluids, and we examined whether SP-D affects surfactant secretion by alveolar type II cells. Native SP-D affected neither basal secretion nor stimulated secretion by type II cells. However, native SP-D counteracted the inhibitory effect of SP-A on surfactant secretion in a concentration-dependent manner; however, SP-D failed to counteract the inhibitory effect of concanavalin A. The activity of SP-D was unaffected by inclusion of excess methyl alpha-mannoside. Excess native SP-D competed with 125I-SP-A for high-affinity binding to type II cells. Heat treatment of SP-D and antibody against SP-D both decreased SP-D activity. Butanol extraction of native SP-D was most effective at destroying SP-D activity and attenuated the ability of the protein to compete with labelled SP-A for binding to type II cells. The butanol-soluble fraction of SP-D possessed the ability to alter the inhibitory effect of SP-A to the same extent as native SP-D. Direct binding of 125I-SP-A on nitrocellulose sheets demonstrated that SP-A could bind native SP-D, but not butanol-extracted SP-D. We conclude that native SP-D alters SP-A activity in type II cells through interaction with it via SP-D-associated lipids.
Kuroki
Y
Y
Department of Biochemistry, Sapporo Medical College, Japan.
Shiratori
M
M
Murata
Y
Y
Akino
T
T
D000818:Animals; D001667:Binding, Competitive; D015153:Blotting, Western; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D006023:Glycoproteins / Q000378:metabolism*; D008766:Methylmannosides / Q000494:pharmacology; D010713:Phosphatidylcholines / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism*; D011510:Proteolipids / Q000378:metabolism* / Q000494:pharmacology; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000378:metabolism*; D037662:Pulmonary Surfactant-Associated Protein A; D037663:Pulmonary Surfactant-Associated Protein D; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D006023:Glycoproteins; D008766:Methylmannosides; D010713:Phosphatidylcholines; D010743:Phospholipids; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037663:Pulmonary Surfactant-Associated Protein D; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; C008466:methylmannoside; D013755:Tetradecanoylphorbol Acetate