Masato Yasui

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Aquaporin (AQP) water-channel proteins are freely permeated by water but not by ions or charged solutes. Although mammalian aquaporins were believed to be located in plasma membranes, rat AQP6 is restricted to intracellular vesicles in renal epithelia. Here we show that AQP6 is functionally distinct from other known aquaporins. When expressed in Xenopus(More)
All characterized mammalian aquaporins (AQPs) are localized to plasma membranes where they function chiefly to mediate water transport across cells. Here we show that AQP6 is localized exclusively in intracellular membranes in renal epithelia. By using a polyclonal antibody to the C terminus of AQP6, immunoblots revealed a major 30-kDa band in membranes(More)
The water permeability of biological membranes has been a longstanding problem in physiology, but the proteins responsible for this remained unknown until discovery of the aquaporin 1 (AQP1) water channel protein. AQP1 is selectively permeated by water driven by osmotic gradients. The atomic structure of human AQP1 has recently been defined. Each subunit of(More)
damental to life. Water constitutes roughly 70% of the mass of most living organisms, so the orderly distribution of water is required to maintain proper fluid balance within different anatomic compartments. Although water is known to diffuse through lipid bilayers, diffusion is not sufficiently rapid for many physiological processes. To accommodate these(More)
Aquaporins (AQP) were originally regarded as plasma membrane channels that are freely permeated by water or small uncharged solutes but not by ions. Unlike other aquaporins, AQP6 overexpressed in Xenopus laevis oocytes was previously found to exhibit Hg2+ or pH-activated ion conductance. AQP6 could not be analyzed electrophysiologically in mammalian cells,(More)
Aquaporin-2 (AQP2), the protein that mediates arginine vasopressin (AVP)-regulated apical water transport in the renal collecting duct, possesses a single consensus phosphorylation site for cAMP-dependent protein kinase A (PKA) at Ser256. The aim of this study was to examine whether AVP, and other agents that increase cAMP levels, could stimulate the(More)
Aquaporin-6 (AQP6) has recently been identified as an intracellular vesicle water channel with anion permeability that is activated by low pH or HgCl2. Here we present direct evidence of AQP6 channel gating using patch clamp techniques. Cell-attached patch recordings of AQP6 expressed in Xenopus laevis oocytes indicated that AQP6 is a gated channel with(More)
Recent discovery of a family of water-specific membrane channel proteins, the aquaporins, has provided new insights into the molecular basis of membrane water permeability. Eleven mammalian aquaporins have been identified to date, with homolog present across the spectrum of life, including bacteria, yeast and plants. The distribution of the mammalian(More)
BACKGROUND INFORMATION Most AQPs (aquaporins) function at the plasma membrane, however AQP6 is exclusively localized to membranes of intracellular vesicles in acid-secreting type-A intercalated cells of renal collecting ducts. The intracellular distribution indicates that AQP6 has a function distinct from trans-epithelial water movement. RESULTS We show(More)
The selectivity of aquaporins for water and solutes is determined by pore diameter. Paradoxically, the wider pores of glycerol facilitators restrict water passage by an unknown mechanism. Earlier we characterized an aquaglyceroporin from Plasmodium falciparum with high permeability for both glycerol and water. We use point mutations to demonstrate that(More)