title: Assessment of the roles of ordered lipid microdomains in post-endocytic trafficking of glycosyl-phosphatidylinositol-anchored proteins in mammalian fibroblasts.
abstract: We have used artificial phosphatidylethanolamine-polyethylene glycol (PE-PEG)-anchored proteins, incorporated into living mammalian cells, to evaluate previously proposed roles for ordered lipid 'raft' domains in the post-endocytic trafficking of glycosylphosphatidylinositol (GPI)-anchored proteins in CHO and BHK cells. In CHO cells, endocytosed PE-PEG protein conjugates colocalized strongly with the internalized GPI-anchored folate receptor, concentrating in the endosomal recycling compartment, regardless of the structure of the hydrocarbon chains of the PE-PEG 'anchor'. However, internalized PE-PEG protein conjugates with long-chain saturated anchors recycled to the plasma membrane at a slow rate comparable to that measured for the GPI-anchored folate receptor, whereas conjugates with short-chain or unsaturated anchors recycled at a faster rate similar to that observed for the transferrin receptor. These findings support the proposal (Mayor et al. Cholesterol-dependent retention of GPI-anchored proteins in endosomes. EMBO J 1998;17:4628-4638) that the slow recycling of GPI proteins in CHO cells rests on their affinity for ordered lipid domains. In BHK cells, internalized PE-PEG protein conjugates with either saturated or unsaturated 'anchors' colocalized strongly with simultaneously endocytosed folate receptor and, like the folate receptor, gradually accumulated in late endosomes/lysosomes. These latter findings do not support previous suggestions that the sorting of GPI proteins to late endosomes in BHK cells depends on their association with lipid rafts.
authors.affiliation: Department of Biochemistry, McGill University, Montréal, Québec, Canada.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Refaei
authors.forename: Rania
authors.initials: R
authors.lastname: Leventis
authors.forename: John R
authors.initials: JR
authors.lastname: Silvius
mesh_terms: D000818:Animals; D016466:CHO Cells; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism*; D058973:Folate Receptors, GPI-Anchored / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000737:chemistry / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism; D021962:Membrane Microdomains / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000737:chemistry / Q000378:metabolism; D011092:Polyethylene Glycols / Q000737:chemistry / Q000378:metabolism; D021381:Protein Transport; D011990:Receptors, Transferrin / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D058973:Folate Receptors, GPI-Anchored; D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; D010714:Phosphatidylethanolamines; D011990:Receptors, Transferrin; D011092:Polyethylene Glycols