Sphingolipids are required for the stable membrane association of glycosylphosphatidylinositol-anchored proteins in yeast.
Ongoing sphingolipid synthesis is specifically required in vivo for the endoplasmic reticulum (ER) to Golgi transport of glycosylphosphatidylinositol (GPI)-anchored proteins. However, the sphingolipid intermediates that are required for transport nor their role(s) have been identified. Using stereoisomers of dihydrosphingosine, together with specific inhibitors and a mutant defective for sphingolipid synthesis, we now show that ceramides and/or inositol sphingolipids are indispensable for GPI-anchored protein transport. Furthermore, in the absence of sphingolipid synthesis, a significant fraction of GPI-anchored proteins is no longer associated tightly with the ER membrane. The loose membrane association is neither because of the lack of a GPI-anchor nor because of prolonged ER retention of GPI-anchored proteins. These results indicate that ceramides and/or inositol sphingolipids are required to stabilize the association of GPI-anchored proteins with membranes. They could act either by direct involvement as membrane components or as substrates for the remodeling of GPI lipid moieties.
Watanabe
Reika
R
Biozentrum of the University of Basel, Klingelbergstrasse 70, Basel 4056, Switzerland.
Funato
Kouichi
K
Venkataraman
Krishnan
K
Futerman
Anthony H
AH
Riezman
Howard
H
D018797:Cell Cycle Proteins; D002462:Cell Membrane / Q000378:metabolism; D002518:Ceramides / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D058851:GPI-Linked Proteins; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism; D050356:Lipid Metabolism; D008565:Membrane Proteins / Q000378:metabolism; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D013107:Sphingolipids / Q000378:metabolism*; D013237:Stereoisomerism; D013379:Substrate Specificity; D015003:Yeasts / Q000378:metabolism
D018797:Cell Cycle Proteins; D002518:Ceramides; C096192:GAS1 protein, human; D058851:GPI-Linked Proteins; D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; D013107:Sphingolipids