title: Association of yeast transporters with detergent-resistant membranes correlates with their cell-surface location.
abstract: Detergent-resistant membrane (DRM) fractions enriched in ergosterol and sphingolipids can be isolated from yeast cells and have been proposed to represent the biochemical equivalents of lipid rafts. Most yeast plasma membrane proteins studied for their detergent solubility have been found in DRMs, except for the Hxt1 and Gap1 permeases. We here compared Gap1 detergent solubility in wild-type and various mutant cells under conditions promoting cell surface accumulation or ubiquitin-dependent down-regulation of the permease. We show that Gap1 present at the plasma membrane is associated with DRMs. This association occurs at the Golgi level. In the absence of sphingolipid neosynthesis, Gap1 fails to accumulate at the plasma membrane and is missorted to the vacuolar lumen. Furthermore, the presence of Gap1 at the plasma membrane correlates perfectly with its association with DRMs, whatever the activity or ubiquitination state of the permease and regardless of whether it has reached the cell surface via normal secretion, after recycling, or upon missorting to the vacuole before rerouting to the plasma membrane. Finally, we show that Hxt1 present at the cell surface is also associated with DRMs. We discuss a model where yeast plasma membrane proteins are systematically associated with sphingolipid/ergosterol-enriched microdomains when located at the cell surface.
authors.affiliation: Laboratoire de Physiologie Moléculaire de la Cellule, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles (ULB), Gosselies, Belgium.
authors.forename: Elsa
authors.initials: E
authors.lastname: Lauwers
authors.forename: Bruno
authors.initials: B
authors.lastname: André
mesh_terms: D026905:Amino Acid Transport Systems / Q000378:metabolism; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology*; D004705:Endocytosis; D051246:Glucose Transport Proteins, Facilitative; D006056:Golgi Apparatus / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D012995:Solubility; D013107:Sphingolipids / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D026905:Amino Acid Transport Systems; D003902:Detergents; C491145:GAP1 protein, S cerevisiae; D051246:Glucose Transport Proteins, Facilitative; C090594:HXT1 protein, S cerevisiae; D009004:Monosaccharide Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D013107:Sphingolipids