title: Biochemical and genetic evidence for the involvement of yeast Ypt6-GTPase in protein retrieval to different Golgi compartments.
abstract: Yeast Ypt6p, the homologue of the mammalian Rab6 GTPase, is not essential for cell viability. Based on previous studies with ypt6 deletion mutants, a regulatory role of the GTPase either in protein retrieval to the trans-Golgi network or in forward transport between the endoplasmic reticulum (ER) and early Golgi compartments was proposed. To assess better the primary role(s) of Ypt6p, temperature-sensitive ypt6 mutants were generated and analyzed biochemically and genetically. Defects in N-glycosylation of proteins passing the Golgi and of Golgi-resident glycosyltransferases as well as protein sorting defects in the trans-Golgi were recorded shortly after functional loss of Ypt6p. ER-to-Golgi transport and protein secretion were delayed but not interrupted. Mis-sorting of the vesicular SNARE Sec22p to the late Golgi was also observed. Combination of the ypt6-2 mutant allele with a number of mutants in forward and retrograde transport between ER, Golgi, and endosomes led to synthetic negative growth defects. The results obtained indicate that Ypt6p acts in endosome-to-Golgi, in intra-Golgi retrograde transport, and possibly also in Golgi-to-ER trafficking.
authors.affiliation: Max Planck Institute for Biophysical Chemistry, Department of Molecular Genetics, D-37070 Göttingen, Germany.
authors.forename: Zongli
authors.initials: Z
authors.lastname: Luo
authors.forename: Dieter
authors.initials: D
authors.lastname: Gallwitz
mesh_terms: D004721:Endoplasmic Reticulum / Q000378:metabolism; D006023:Glycoproteins / Q000032:analysis; D006031:Glycosylation; D016695:Glycosyltransferases / Q000502:physiology; D006056:Golgi Apparatus / Q000378:metabolism*; D020559:Monomeric GTP-Binding Proteins / Q000502:physiology*; D009154:Mutation; D021381:Protein Transport; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013696:Temperature; D020691:rab GTP-Binding Proteins / Q000502:physiology
chemical_list: D006023:Glycoproteins; D029701:Saccharomyces cerevisiae Proteins; D016695:Glycosyltransferases; C060755:YPT1 protein, S cerevisiae; D020559:Monomeric GTP-Binding Proteins; C499307:YPT6 protein, S cerevisiae; D020691:rab GTP-Binding Proteins