INTRACELLULAR-TRANSPORT OF GPI-ANCHORED PROTEINS BY YEAST

We have investigated the effects of an inhibitor of ceramide biosynthe sis on the glycosylphosphatidylinositol (GPI)-anchoring and intracellu lar transport of the yeast Gas1 protein. No effect on anchor attachmen t was demonstrable, but a selective delay in transport from the endopl asmic reticulum to the Golgi complex was observed. The compound also b locked remodeling of GPI-anchors from their base-sensitive to base-res istant forms. A recessive mutation was found that caused resistance to the drug, restored transport of Gas1p, but did not restore ceramide b iosynthesis in the presence of the inhibitor. Our results suggest that intracellular transport of GPI-anchored proteins is stimulated by new ceramide synthesis. The role of ceramide may be direct or may be thro ugh its use in the remodeling of GPI-anchored proteins other than Gas1 p. The need for ceramide can be overcome in the mutant strain.