N‐Stearoyl‐phosphatidylserine: Synthesis and role in divalent‐cation‐induced aggregation and fusion

N‐Acylphosphatidylserines have been isolated from intact and injured tissues, but the participation of such acidic phospholipids in membrane aggregation and fusion has not been demonstrated. We have synthesized N‐stearoylphosphatidylserine (NSPS) and examined divalent‐cation‐induced aggregation of N...

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Bibliographic Details
Published in:Lipids 1998-06, Vol.33 (6), p.607-616
Main Authors: Morillo, Margarita, Sagristá, M. Luisa, Madariaga, M. Africa
Format: Article
Language:English
Subjects:
Calcium
Cations, Divalent - pharmacology
Chemical degradation
In Vitro Techniques
Liposomes
Magnesium
Magnetic Resonance Spectroscopy
Membrane Fusion - drug effects
Membrane Lipids - chemistry
Microscopy, Electron
NMR
Nuclear magnetic resonance
Particle Size
Phosphatidylserines - chemical synthesis
Phosphatidylserines - chemistry
Phosphatidylserines - metabolism
Phospholipase D - metabolism
Spectrophotometry, Infrared
Streptomyces - enzymology
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Summary:N‐Acylphosphatidylserines have been isolated from intact and injured tissues, but the participation of such acidic phospholipids in membrane aggregation and fusion has not been demonstrated. We have synthesized N‐stearoylphosphatidylserine (NSPS) and examined divalent‐cation‐induced aggregation of NSPS‐liposomes, which leads to membrane destabilization and fusion. The purified lipid was characterized by its chromatographic and spectroscopic (infrared and 1H nuclear magnetic resonance) properties and by its chemical degradation pattern. Aggregation of unilamellar NSPS‐liposomes was studied as a function of calcium and magnesium concentration. The ability of calcium and magnesium to induce vesicle aggregation is higher for phosphatidylserine (PS)‐liposomes (threshold concentration 1.5 mM for calcium and 4.6 mM for magnesium) than for NSPS‐liposomes (threshold concentration 2.8 mM for calcium and 6.6 mM for magnesium). The irreversibility of the aggregation reactions after adding EDTA suggests that vesicle fusion might occur in the presence of calcium and magnesium. Preliminary studies, based on mixing of both lipid and internal aqueous contents, show that fusion rather than aggregation of NSPS‐liposomes occurs in the presence of calcium ions. The tendency of NSPS‐liposomes to aggregate at higher cation concentrations than PS‐liposomes suggests that N‐acylation of phosphatidylserine protects the membrane against degenerative damage caused by aggregation and fusion.
ISSN:0024-4201
1558-9307
DOI:10.1007/s11745-998-0247-1