GPI-anchored proteins are attached to the membrane via a glycosylphosphatidylinositol-(GPI) anchor whose carbohydrate core is conserved in all eukaryotes. Apart from membrane attachment, the precise role of the GPI-anchor is not known, but it has been proposed to play a role in protein sorting. We have investigated the transport of the yeast GPI-anchored protein Gas1p. We identified two mutant strains involved in very different cellular processes that are blocked selectively in the transport of GPI-anchored proteins before arrival to the Golgi. The end8-1/lcb1-100 mutant is defective in ceramide synthesis. In vitro data suggest a requirement for ceramides after the exit from the ER. We therefore propose that ceramides might function in the fusion of a GPI-containing vesicle with the Golgi, but we cannot exclude a role in the ER. The second mutant that blocks the transport of GPI-anchored proteins to the Golgi is ret1-1, a mutant in the alpha-subunit of coatomer. In both mutants, GPI-anchor attachment is normal and in ret1-1 cells, the GPI-anchors are remodeled with ceramide to the same extent as in wild-type cells.
Specific requirements for the ER to Golgi transport of GPI-anchored proteins in yeast
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C. Sutterlin, T.L. Doering, F. Schimmoller, S. Schroder, H. Riezman; Specific requirements for the ER to Golgi transport of GPI-anchored proteins in yeast. J Cell Sci 1 November 1997; 110 (21): 2703–2714. doi: https://doi.org/10.1242/jcs.110.21.2703
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