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  • Functional expression of the human CHIP28 water channel in a yeast secretory mutant
    Publication . Laizé, Vincent; Rousselet, G.; Verbavatz, J. M.; Berthonaud, V.; Gobin, R.; Roudier, N.; Abrami, L.; Ripoche, P.; Tacnet, F.
    The temperature-sensitive Saccharomyces cerevisiae mutant strain NY17, deficient in the secretory pathway (sec6-4 mutation), is used for the heterologous expression of the human CHIP28 water channel. After a heat-shock, the protein is present in partially purified post-golgi secretory vesicles, lmmunodetection and water transport studies, directly made on the vesicles, showed that CHIP28 is highly expressed and active in the yeast membranes.
  • Molecular and functional study of AQY1 from Saccharomyces cerevisiae: role of the C-terminal domain
    Publication . Laizé, Vincent; Gobin, R.; Rousselet, G.; Badier, C.; Hohmann, S.; Ripoche, P.; Tacnet, F.
    The yeast YPR192w gene, which encodes a protein (Aqy1p) with strong homology to aquaporins (AQPs), was cloned from nine S. cerevisiae strains. The osmotic water permeability coefficient (Pf) of X. laevis oocytes expressing the gene cloned from the S1278b strain (AQY1-1) was 5.7 times higher than the Pf of oocytes expressing the gene cloned from other strains (AQY1-2). Aqy1-1p, initially cloned without its C-terminus (Aqy1-1DCp), mediated an ;3 times higher water permeability than the full-length protein. This corresponds to a 3-fold higher protein density in the oocyte plasma membrane, as shown by freeze-fracture electron microscopy. Pf measurements in yeast spheroplasts confirmed the presence of functional water channels in S1278b and a pharmacological study indicated that this strain contains at least a second functional aquaporin.
  • Purification and functional reconstitution of the human CHIP28 water channel expressed in Saccharomyces cerevisiae
    Publication . Laizé, Vincent; Ripoche, P.; Tacnet, F.
    The yeast Saccharomyces cerevisiae was used for these proteins are of primary importance to appreciate heterologous expression of the human CHIP28 water their physiological role in living organisms. Aquaporin-1 channel (Aquaporin-1). A nine-amino- Recently, CHIP28 was expressed functionally in acid epitope of the influenza hemagglutinin protein yeast secretory vesicles in our laboratory (3). This work (HA epitope), recognized by the monoclonal antibody indicated that wild-type or mutant aquaporins could 12CA5, was chosen to tag CHIP28 at its N-terminus. be produced easily in this new heterologous expression Epitope-tagged CHIP28 was purified from yeast ex- system for functional analyses. Such studies are fretracts by immunochromatography on protein A/ quently limited in the other known expression systems, 12CA5-coupled beads, after KI extraction and deter- mainly due to maturation or sorting defects (4). It begent solubilization, then concentrated by anion ex- came possible to produce large amounts of aquaporins change chromatography. Purified protein was recon- from yeast cultures for biochemical and biophysical stituted in proteoliposomes and was shown to function studies. Here, we describe a simple method to purify as a water channel by stopped-flow spectrophotome- try. This study demonstrates that the yeast has the yeast-expressed CHIP28, after addition of an epitope capacity to produce functional aquaporins at levels tag at the protein N-terminus. The purification procesufficient for biochemical and biophysical analyses.