Spontaneous insertion and partitioning of alkaline phosphatase into model lipid rafts.
Several cell surface eukaryotic proteins have a glycosylphosphatidylinositol (GPI) modification at the C-terminal end that serves as an anchor to the plasma membrane and could be responsible for the presence of GPI proteins in rafts, a type of functionally important membrane microdomain enriched in sphingolipids and cholesterol. In order to understand better how GPI proteins partition into rafts, the insertion of the GPI-anchored alkaline phosphatase (AP) was studied in real-time using atomic force microscopy. Supported phospholipid bilayers made of a mixture of sphingomyelin-dioleoylphosphatidylcholine containing cholesterol (Chl+) or not (Chl-) were used to mimic the fluid-ordered lipid phase separation in biological membranes. Spontaneous insertion of AP through its GPI anchor was observed inside both Chl+ and Chl- lipid ordered domains, but AP insertion was markedly increased by the presence of cholesterol.
Milhiet
Pierre-Emmanuel
PE
Centre de Biochimie Structurale, CNRS UMR 5048 Université Montpellier I, INSERM UMR554, 29 rue de Navacelles, F-34090 Montpellier cedex, France.
Giocondi
Marie-Cécile
MC
Baghdadi
Omid
O
Ronzon
Frédéric
F
Roux
Bernard
B
Le Grimellec
Christian
C
D000469:Alkaline Phosphatase / Q000378:metabolism*; D021962:Membrane Microdomains / Q000201:enzymology*; D018625:Microscopy, Atomic Force; D010713:Phosphatidylcholines / Q000378:metabolism; D013107:Sphingolipids / Q000378:metabolism
D010713:Phosphatidylcholines; D013107:Sphingolipids; D000469:Alkaline Phosphatase; C017251:1,2-oleoylphosphatidylcholine