Gyp5p and Gyl1p are involved in the control of polarized exocytosis in budding yeast.
We report here elements for functional characterization of two members of the Saccharomyces cerevisiae Ypt/Rab GTPase activating proteins family (GAP): Gyp5p, a potent GAP in vitro for Ypt1p and Sec4p, and the protein Ymr192wp/APP2 that we propose to rename Gyl1p (GYp like protein). Immunofluorescence experiments showed that Gyp5p and Gyl1p partly colocalize at the bud emergence site, at the bud tip and at the bud neck during cytokinesis. Subcellular fractionation and co-immunoprecipitation experiments showed that Gyp5p and Gyl1p co-fractionate with post-Golgi vesicles and plasma membrane, and belong to the same protein complexes in both localizations. We found by co-immunoprecipitation experiments that a fraction of Gyp5p interacts with Sec4p, a small GTPase involved in exocytosis, and that a fraction of Gyl1p associates at the plasma membrane with the Gyp5p/Sec4p complexes. We showed also that GYP5 genetically interacts with SEC2, which encodes the Sec4p exchange factor. Examination of the gyp5Deltagyl1Delta mutants grown at 13 degrees C revealed a slight growth defect, a secretion defect and an accumulation of secretory vesicles in the small-budded cells. These data suggest that Gyp5p and Gyl1p are involved in control of polarized exocytosis.
Institut de Génétique et Microbiologie, CNRS-UMR 8621, Université Paris XI, 91 405 Orsay Cédex, France.
Laurent
L
Chesneau
Sophie
S
Dupré
Anna
A
Burdina
Jérôme
J
Roger
Sophie
S
Le Panse
Michel
M
Jacquet
Marie-Hélène
MH
Cuif
D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D003080:Cold Temperature; D005089:Exocytosis / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors; D046912:Multiprotein Complexes; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D043324:beta-Fructofuranosidase / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; C504621:Gyl1 protein, S cerevisiae; C504620:Gyp5 protein, S cerevisiae; D046912:Multiprotein Complexes; D011993:Recombinant Fusion Proteins; C064456:SEC2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D043324:beta-Fructofuranosidase; D019204:GTP-Binding Proteins; C064320:SEC4 protein, S cerevisiae; D020691:rab GTP-Binding Proteins