Existence of a tightly regulated water channel in Saccharomyces cerevisiae.
The Saccharomyces cerevisiae strain Sigma1278b possesses two putative aquaporins, Aqy1-1p and Aqy2-1p. Previous work demonstrated that Aqy1-1p functions as a water channel in Xenopus oocyte. However, no function could be attributed to Aqy2-1p in this system. Specific antibodies were used to follow the expression of Aqy1-1p and Aqy2-1p in the yeast. Aqy1-1p was never detected whatever the growth phase and culture conditions tested. In contrast, Aqy2-1p was detected only during the exponential growth phase in rich medium containing glucose. Aqy2-1p expression was repressed by hyper-osmotic culture conditions. Both immunocytochemistry and biochemical subcellular fractionation demonstrated that Aqy2-1p is located on the endoplasmic reticulum (ER) as well as on the plasma membrane. In microsomal vesicles enriched in ER, a water channel activity due to Aqy2-1p was detected by stopped-flow analysis. Our results show that the expression of aquaporins is tightly controlled. The physiological relevance of aquaporin-mediated water transport in yeast is discussed.
Meyrial
V
V
Département de Biologie Cellulaire et Moléculaire, SBCe, CEA/Saclay, Gif sur Yvette cedex F-91191, France.
Laizé
V
V
Gobin
R
R
Ripoche
P
P
Hohmann
S
S
Tacnet
F
F
D020346:Aquaporins / Q000302:isolation & purification / Q000502:physiology*; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D017022:Flow Injection Analysis; D005656:Fungal Proteins / Q000502:physiology; D015966:Gene Expression Regulation, Fungal; D008861:Microsomes / Q000378:metabolism; D009997:Osmotic Pressure; D011994:Recombinant Proteins; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D014867:Water / Q000378:metabolism*
C115153:AQY1 protein, S cerevisiae; C422454:AQY2 protein, S cerevisiae; D020346:Aquaporins; D005656:Fungal Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D014867:Water