Temperature-dependent localization of GPI-anchored intestinal alkaline phosphatase in model rafts.
In plasma membranes, most of glycosylphosphatidylinositol (GPI)-anchored proteins would be associated with rafts, a category of ordered microdomains enriched in sphingolipids and cholesterol (Ch). They would be also concentrated in the detergent resistant membranes (DRMs), a plasma membrane fraction extracted at low temperature. Preferential localization of GPI-anchored proteins in these membrane domains is essentially governed by their high lipid order, as compared to their environment. Changes in the temperature are expected to modify the membrane lipid order, suggesting that they could affect the distribution of GPI-anchored proteins between membrane domains. Validity of this hypothesis was examined by investigating the temperature-dependent localization of the GPI-anchored bovine intestinal alkaline phophatase (BIAP) into model raft made of palmitoyloleoylphosphatidylcholine/sphingomyelin/cholesterol (POPC/SM/Chl) supported membranes. Atomic force microscopy (AFM) shows that the inserted BIAP is localized in the SM/Chl enriched ordered domains at low temperature. Above 30 degrees C, BIAP redistributes and is present in both the 'fluid' POPC enriched and the ordered SM/Chl domains. These data strongly suggest that in cells the composition of plasma membrane domains at low temperature differs from that at physiological temperature.
Giocondi
Marie-Cécile
MC
Institut National de la Santé et de la Recherche Médicale, Unité 554, Montpellier, France.
Besson
Françoise
F
Dosset
Patrice
P
Milhiet
Pierre-Emmanuel
PE
Le Grimellec
Christian
C
D000469:Alkaline Phosphatase / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D017261:Glycosylphosphatidylinositols / Q000737:chemistry / Q000378:metabolism*; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism*; D008560:Membrane Fluidity / Q000502:physiology; D021962:Membrane Microdomains / Q000378:metabolism* / Q000648:ultrastructure*; D018625:Microscopy, Atomic Force; D008954:Models, Biological; D013696:Temperature; D014018:Tissue Distribution
D017261:Glycosylphosphatidylinositols; D007527:Isoenzymes; C415670:Alpi protein, rat; D000469:Alkaline Phosphatase