The role of the palmitoylation of surfactant associated protein c
in surfactant film formation and stability.
Qanbar, Riad, Stanley Cheng, Fred Possmayer, and Samuel
Sch[umlaut]urch.
MRC group in Fetal and Neonatal Health and Development, Departments
of Biochemistry and Obstetrics and Gynaecology, The University of
Western Ontario, London, Ontario N6A 5A5, Canada and Respiratory
Research Group, Faculty of Medicine, The University of Calgary,
Calgary, Alberta T2N 4N1, Canada
APStracts 3:0092L, 1996.
The effect of palmitoylation of pulmonary surfactant-associated
protein C (SP-C) on the surface activity of phospholipid mixtures of
dipalmitoylphosphatidylcholine and phosphatidylglycerol was studied.
Phospholipids reconstituted with palmitoylated or depalmitoylated
bovine SP-C were examined at neutral and acidic pH using a captive
bubble surfactometer. At low pH, effective lipid adsorption and near
zero surface tensions upon compression were obtained even with
protein-free samples. At physiological pH, only SP-C-containing
samples achieved such properties. Lipid adsorption was decreased by
prior SP-C depalmitoylation. Bubbles with palmitoylated SP-C were
more mechanically stable and required less compression to reach low
surface tensions. Subphase depletion experiments showed that
dynamically cycled surface layers containing palmitoylated SP-C
maintained their surface activity after subphase lipid depletion. In
contrast, surface activity was rapidly lost where depalmitoylated SP
-C or SP-B were included. Our results indicate that although SP-C
palmitoylation has little effect on its ability to enhance lipid
adsorption and surface tension reduction, it greatly enhances lipid
respreading and film stability and is therefore important for
surfactant function.
Received 21 July 1995; accepted in final form 21 May 1996.
APS Manuscript Number L228-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 17 June 96