Phosphatidylethanol counteracts calcium-induced membrane fusion but promotes proton-induced fusion.
The susceptibility of phosphatidylethanol-containing lipid vesicles towards Ca2+- and proton-induced fusion has been investigated, using a system of interacting vesicles. The results show that phosphatidylethanol-rich vesicles are quite resistant to Ca2+-induced fusion while being highly sensitive to proton-induced fusion. Inclusion of phosphatidylethanol was also found to promote and inhibit, respectively, the proton-induced and Ca2+-induced fusion of bilayer vesicles containing also phosphatidylethanolamine and either phosphatidylserine or phosphatidic acid. Thus, phosphatidylethanol affected Ca2+- and proton-induced fusion in opposite directions, in contrast to the naturally occurring anionic phospholipids phosphatidic acid, phosphatidylserine and phosphatidylinositol, which affect the sensitivity to Ca2+- and H+-induced fusion in the same direction. However, the fusion competence of phosphatidylethanol vesicles in response to both Ca2+ and H+ was inversely related to the apparent thickness of the polar headgroup layer, determined by using lectin-glycolipid interaction as a steric probe, as previously found for vesicles containing naturally occurring anionic phospholipids.
D000371:Agglutination; D002118:Calcium; D002352:Carrier Proteins / Q000097:blood*; D005456:Fluorescent Dyes; D020404:Glycerophospholipids; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D037102:Lectins; D008051:Lipid Bilayers; D008565:Membrane Proteins / Q000097:blood; D008954:Models, Biological; D010712:Phosphatidic Acids; D010714:Phosphatidylethanolamines; D010718:Phosphatidylserines; D028021:Sodium-Potassium-Chloride Symporters
D002352:Carrier Proteins; D005456:Fluorescent Dyes; D020404:Glycerophospholipids; D037102:Lectins; D008051:Lipid Bilayers; D008565:Membrane Proteins; D010712:Phosphatidic Acids; D010714:Phosphatidylethanolamines; D010718:Phosphatidylserines; D028021:Sodium-Potassium-Chloride Symporters; C051521:phosphatidylethanol; D002118:Calcium