Protein-lipid interactions and enzyme requirements for light subtype generation on cycling reconstituted surfactant.
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.
Dhand
R
R
Division of Pulmonary and Critical Care Medicine, Edward Hines Jr. Veterans Affairs Hospital, Hines, Illinois, USA.
Sharma
V K
VK
Teng
A L
AL
Krishnasamy
S
S
Gross
N J
NJ
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
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