title: Protein-lipid interactions and enzyme requirements for light subtype generation on cycling reconstituted surfactant.
abstract: Surfactant convertase is required for conversion of heavy density (H) natural surfactant to light density (L) subtype during cycling in vitro, a technique that reproduces surfactant metabolism. To study mechanisms of H to L conversion, we prepared liposomes of dipalmitoylphosphatidylcholine (DPPC) and phosphatidylglycerol (PG), or the phospholipids (PL) in combination with either surfactant protein A (SP-A), surfactant protein B (SP-B), or both SP-A and SP-B. Phospholipids alone showed time-dependent conversion from heavy to light subtype on cycling in the absence of convertase, which was decreased by adding SP-B, but not SP-A, to phospholipids (p < 0.01 for PL+SP-B, or PL+SP-A+SP-B vs. PL, or PL+SP-A). The ultrastructure, surface activity, buoyant density, and L subtype generation on cycling PL+SP-A+SP-B with partially purified convertase or with phospholipase D were similar to those of natural TM. In conclusion, a reconstituted surfactant mimics the behavior of natural surfactant on cycling, and reveals that interaction of SP-B with phospholipids decreases L subtype generation. In addition, esterase/ phospholipase D activity is required for conversion of heavy to light subtype on cycling.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Edward Hines Jr. Veterans Affairs Hospital, Hines, Illinois, USA.
authors.forename: R
authors.initials: R
authors.lastname: Dhand
authors.forename: V K
authors.initials: VK
authors.lastname: Sharma
authors.forename: A L
authors.initials: AL
authors.lastname: Teng
authors.forename: S
authors.initials: S
authors.lastname: Krishnasamy
authors.forename: N J
authors.initials: NJ
authors.lastname: Gross
mesh_terms: D000818:Animals; D001688:Biological Products; D005260:Female; D051379:Mice; D009186:Myelin Sheath; D010739:Phospholipase D / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D011506:Proteins; D011510:Proteolipids / Q000378:metabolism / Q000648:ultrastructure; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000145:classification / Q000378:metabolism* / Q000648:ultrastructure; D012697:Serine Endopeptidases / Q000378:metabolism; D013046:Specific Gravity
chemical_list: D001688:Biological Products; D010743:Phospholipids; D011506:Proteins; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; C018167:tubular myelin; D010739:Phospholipase D; D012697:Serine Endopeptidases; C068328:surfactant subtype convertase