Phospholipid-Diacylglycerol Complexes Regulate Colipase Adsorption to Monolayers

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• 作者：Nancy K. Mizuno ; Janice M. Smaby ; Beth A. Cunningham ; Maureen M. Momsen ; and Howard L. Brockman
• 刊名：Langmuir
• 出版年：2003
• 出版时间：March 4, 2003
• 年：2003
• 卷：19
• 期：5
• 页码：1802 - 1808
• 全文大小：124K
• 年卷期：v.19,no.5(March 4, 2003)
• ISSN：1520-5827

文摘

Monomolecular films of a 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine and any of several non-phospholipids, like diacylglycerols and free fatty acids, inhibit the initial rate of adsorption of an amphipathicprotein, colipase, more effectively than the same two-dimensional concentration of phosphatidylcholinealone, even though the non-phospholipids alone have no effect [Sugar, I. P.; Mizuno, N. K.; Momsen, M.M.; Brockman, H. L. Biophys. J. 2001, 81, 3387-3397]. Inhibition correlates with complex formationbetween the phosphatidylcholine and non-phospholipid constituents of the monolayer. In the presentstudy, we have examined the formation of complexes of 1,3-dioleoylglycerol with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and other species more representative of the phospholipid classes more typicallyfound in the inner leaflet of cellular plasma membranes. These were bovine liver phosphatidylinositol and1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine, -phosphoserine, and -phosphate. Analysis of surfacepressure-surface potential-molecular area isotherms showed that all phospholipid species tested weremiscible with and formed complexes with 1,3-dioleoylglycerol. Complex compositions were in the rangeof 0.14-0.25 mole fraction of diacylglycerol. For the phosphatidylcholine, phosphatidylethanolamine,phosphatidylserine, and phosphatidylinositol mixtures with diacylglycerol at surface pressures near collapse,the initial rate of adsorption of colipase was near zero up to at least the complex composition. With increasingdiacylglycerol, the initial adsorption rate increased rapidly to the value observed in the absence of lipid.In contrast, adsorption rates with the phosphatidic acid species increased rapidly beginning at lowdiacylglycerol mole fractions and were half-maximal at the complex composition. All the data could beanalyzed successfully with a statistical model based on the phospholipid exhibiting an excluded area thatis independent of overall lipid composition and packing. Values of the excluded areas obtained from theanalysis showed an approximate 1:1 correspondence with molecular areas of the complexes, assuming nocomplex for phosphatidic acid. This study shows that phospholipid classes of the type typically exposedto peripheral proteins in the cytoplasm of cells can complex with non-phospholipid second messengers, likediacylglycerols, that are generated in the inner leaflet in response to ligand-receptor interaction on thecell surface. Thus, their complexation with phospholipids has the potential, as for colipase binding, toregulate the translocation of peripheral proteins to the plasma membrane.