title: Stable cell surface expression of GPI-anchored proteins, but not intracellular transport, depends on their fatty acid structure.
abstract: Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are a class of lipid anchored proteins expressed on the cell surface of eukaryotes. The potential interaction of GPI-APs with ordered lipid domains enriched in cholesterol and sphingolipids has been proposed to function in the intracellular transport of these lipid anchored proteins. Here, we examined the biological importance of two saturated fatty acids present in the phosphatidylinositol moiety of GPI-APs. These fatty acids are introduced by the action of lipid remodeling enzymes and required for the GPI-AP association within ordered lipid domains. We found that the fatty acid remodeling is not required for either efficient Golgi-to-plasma membrane transport or selective endocytosis via GPI-enriched early endosomal compartment (GEEC)/ clathrin-independent carrier (CLIC) pathway, whereas cholesterol depletion significantly affects both pathways independent of their fatty acid structure. Therefore, the mechanism of cholesterol dependence does not appear to be related to the interaction with ordered lipid domains mediated by two saturated fatty acids. Furthermore, cholesterol extraction drastically releases the unremodeled GPI-APs carrying an unsaturated fatty acid from the cell surface, but not remodeled GPI-APs carrying two saturated fatty acids. This underscores the essential role of lipid remodeling to ensure a stable membrane association of GPI-APs particularly under potential membrane lipid perturbation.
authors.affiliation: Department of Biochemistry, University of Geneva Sciences II, CH1-1211 Geneva, Switzerland.
authors.forename: Nina
authors.initials: N
authors.lastname: Jaensch
authors.forename: Ivan R
authors.initials: IR
authors.lastname: Corrêa
authors.forename: Reika
authors.initials: R
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D011992:Endosomes / Q000378:metabolism*; D005227:Fatty Acids / Q000737:chemistry* / Q000378:metabolism; D058851:GPI-Linked Proteins / Q000737:chemistry / Q000378:metabolism*; D021381:Protein Transport
chemical_list: D005227:Fatty Acids; D058851:GPI-Linked Proteins; D002784:Cholesterol
keywords: GPI-enriched early endosomal compartment; SNAP-tag technology; cholesterol; clathrin-independent carrier; endocytosis; glycosylphosphatidylinositol-anchored proteins; golgi apparatus; intracellular protein transport; lipid rafts; lipid remodeling; ordered lipid domains