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J Biol Chem, Vol. 273, Issue 38, 24737-24743, September 18, 1998

Molecular Characterization of a Broad Selectivity Neutral Solute Channel^*

Hiroyasu Tsukaguchi, Chairat Shayakul^§, Urs V. Berger, Bryan Mackenzie^¶, Sreenivas Devidas, William B. Guggino, Alfred N. van Hoek^**, and Matthias A. Hediger^§§

From the Renal Division, Department of Medicine, Brigham & Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, the  Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, and the ^** Renal Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02129

	ABSTRACT

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In all living cells, coordination of solute and water movement across cell membranes is of critical importance for osmotic balance. The current concept is that these processes are of distinct biophysical nature. Here we report the expression cloning of a liver cDNA encoding a unique promiscuous solute channel (AQP9) that confers high permeability for both solutes and water. AQP9 mediates passage of a wide variety of non-charged solutes including carbamides, polyols, purines, and pyrimidines in a phloretin- and mercury-sensitive manner, whereas amino acids, cyclic sugars, Na⁺, K⁺, Cl, and deprotonated monocarboxylates are excluded. The properties of AQP9 define a new evolutionary branch of the major intrinsic protein family of aquaporin proteins and describe a previously unknown mechanism by which a large variety of solutes and water can pass through a single pore, enabling rapid cellular uptake or exit of metabolites with minimal osmotic perturbation.

	INTRODUCTION

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Transport of solutes such as ions, nutrients, neurotransmitters, and metabolic waste products across cell membranes is of fundamental importance to all mammalian cells. Despite the identification of many selective solute transporters and water channels (1-4), it has remained unclear how transport of large amounts of solutes is coordinated with water movement in metabolically highly active cells such as hepatocytes, spermatocytes, neurons, and glia. The liver is a major site of production and elimination of metabolites such as urea, nucleotides, and ketone bodies, and substantial amounts of these solutes must rapidly cross the hepatocyte plasma membrane with minimal osmotic perturbation (5). In testis, a solute transport mechanism is presumably required to supply nutrients to rapidly growing spermatocytes and to provide an exit pathway for metabolites. In brain, regulation of solute transport is critical because osmolality changes in extracellular fluids can affect neuronal cell function (6).

Among metabolically active tissues, liver was selected as a target for expression cloning of a new solute-transporting protein because a phloretin-sensitive urea exit mechanism had been described (7-9).

	MATERIALS AND METHODS

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Expression Cloning-- Total RNA was extracted from rats fed a high protein diet (50%, w/w) for 2 weeks. Poly(A)⁺ RNA purified by oligo(dT) chromatography was size-fractionated by preparative agarose gel electrophoresis (30). Specific fractions were screened for 1 mM [¹⁴C]urea uptake activity in RNA-injected Xenopus oocytes (4, 30). A directional cDNA library was constructed from the positive fraction by using the SuperScript Plasmid System (Life Technologies, Inc.), and cDNA clones were screened for urea uptake (4).

Northern Analysis and in Situ Hybridization-- Poly(A)⁺ RNA (3 µg) from rat tissues was electrophoresed in a formaldehyde-agarose gel and transferred to a nylon membrane. The filter was probed with ³²P-labeled full-length AQP9¹ cDNA, hybridized at 42 °C, and washed with 0.1% SDS, 0.1× SSC, at 65 °C. Autoradiography was performed at 80 °C for 5 days. Digoxigenin-labeled sense and antisense probes were synthesized as described (10) and hybridized on 12-µm cryosections of fresh-frozen rat liver and testis. The hybridized probes were visualized using digoxigenin Fab fragment (Boehringer Mannheim) and bromochloroindolyl phosphate/nitro blue tetrazolium substrate.

Oocyte Expression and Radiotracer Uptake Assay-- AQP9-cRNA was synthesized from pSPORT1 after linearization with NotI, using T7 RNA polymerase. Human AQP1-cDNA (a gift of Dr. Peter Agre) and rat AQP3-cDNA (a gift of Dr. Gustavo Frindt) were prepared as described previously (11, 12). AQP1-cRNA (10 ng), AQP3-cRNA, and AQP9-cRNA (25 ng) were injected into collagenase-treated, manually defolliculated oocytes maintained at 18 °C for 2-3 days prior to assays. Radiotracer studies were performed as described (10). Briefly, oocytes were incubated for 90 s with Barth's solution (88 mM NaCl, 1 mM KCl, 0.33 mM Ca(NO₃)₂, 0.41 mM CaCl₂, 0.82 mM MgSO₄, 2.4 mM NaHCO₃, 10 mM HEPES, pH 7.4) including 1 mM unlabeled compound and 1-2 µCi/ml radiolabeled compound. Uptake was terminated by adding ice-cold Barth's solution with 1 mM unlabeled compound, and oocytes were solubilized in 200 µl of 10% SDS. P_s (where P_s indicates diffusive solute permeability coefficient (cm/s)) was determined from the following relation: P_s = N/(A × c), where N is radiotracer uptake (pmol/s); A is the membrane area (0.045 cm²), and c is the concentration difference of the solute (in pmol/cm³). The Arrhenius activation energy was calculated from P_s values at 4, 22, and 30 °C.

Volumetric Assays-- Water permeability was determined by volumetric swelling induced by hypotonic perturbation of oocytes (12). The oocytes were transferred from 200 to 70 mosm of diluted Barth's solution at 22 °C; oocyte swelling was monitored by video microscopy, and the coefficient of osmotic water permeability (P_f) was determined. The Arrhenius activation energy was calculated from P_f at 4, 22, and 30 °C. Iso-osmotic swelling assays were performed as described (11). Briefly, the swelling rate of the oocytes was measured by a video microscope every 10 s for 2 min, after transferring the oocytes from standard Barth's solution to modified Barth's solution in which 88 mM NaCl was replaced by solutes (adjusted to final osmolality of 200 ± 20 mosm) or water. Osmolality was measured by freezing point depression.

Electrophysiological Studies-- A two-microelectrode voltage clamp (Dagan Clampator-1B) was used to measure currents in water-injected oocytes and oocytes expressing AQP1 or AQP9. Microelectrodes (1-5 M) were filled with 3 M KCl. Oocytes were superfused at 23 ± 1 °C in Barth's medium and clamped at a holding potential of 50 mV. Step changes in membrane potential (between +50 and 150 mV, in 20-mV increments) were applied for a duration of 100 ms. Current was filtered at 500 Hz, digitized at 5 kHz, and acquired using the Digidata1200 interface and pCLAMP6 software (Axon Instruments). The steady-state current-voltage relationships were determined with the help of software written by Donald D. F. Loo, UCLA School of Medicine. Functional expression of AQP9 or AQP1 in individual oocytes used for voltage-clamp experiments was subsequently confirmed by radiotracer uptakes or osmotic swelling (lysis) measurements.

	RESULTS AND DISCUSSION

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Expression Cloning of AQP9 cDNA-- We first determined 1 mM [¹⁴C]urea uptake in Xenopus oocytes injected with rat liver mRNA. RNA-injected oocytes exhibited a 2-fold increase in urea uptake compared with water-injected controls (Fig. 1A). When rats were fed a high protein diet, liver mRNA injection induced an 8-fold increase in urea uptake. Liver mRNA from rats fed a high protein diet was fractionated by preparative agarose gel electrophoresis (4), and fractions were analyzed by oocyte expression. A fraction of size 1.5-2.0 kb maximally stimulated urea uptake (12-fold above background, data not shown). This fraction was used to construct a cDNA library from which we isolated a 1.5-kb cDNA that encodes a 295-amino acid residue hydrophobic protein, AQP9. AQP9 has low-to-moderate homology with the mammalian aquaporins AQP3 (48% identity) (11, 13, 14), AQP7 (46% identity) (15), AQP1 (30% identity) (1-3), and with the bacterial glycerol facilitator GlpF (37% identity) (16) (Fig. 1, B and C). A homologue of AQP9 was recently reported from human leucocytes (17), but its unique properties have not yet been investigated. There is no significant homology with members of the urea transporter family. Kyte-Doolittle hydropathy analysis predicted six transmembrane domains separated by five connecting loops (Fig. 1D). AQP9 has two Asn-Pro-Ala (NPA) consensus motifs, characteristic of members of the major intrinsic protein (MIP) family (1-3) (Fig. 1B).

View larger version (41K): [in this window] [in a new window]   Fig. 1.   Expression cloning and deduced amino acid sequence of AQP9. A, uptake of 1 mM [14C]urea in Xenopus oocytes injected with 50 ng of poly(A)+ RNA from rats fed normal and high protein (50% w/w) diets. B, amino acid sequence alignment of AQP9, rat AQP1 (GenBankTM P29975), rat AQP3 (GenBankTM L35108), rat AQP7 (GenBankTM AB000507), and Escherichia coli GlpF (GenBankTM M55990) was performed using the PILEUP program (Genetics Computer Group). Putative membrane-spanning regions are underlined and numbered 1-6. Conserved residues are indicated by shading. Asn-Pro-Ala (NPA) consensus motifs are highlighted by boxes. The potential sites for N-linked glycosylation (Asn-142) (double line), protein kinase C phosphorylation site (Ser-222), and casein kinase II phosphorylation site (Ser-271) (asterisks) are depicted. No consensus motifs of protein kinase A phosphorylation were found. C, phylogenic analysis of AQP9. Deduced amino acid sequences were analyzed using PILEUP. The percent amino acid identity between AQP9 and others is indicated. D, structural model of AQP9. Topology was determined according to the Kyte-Doolittle algorithm. The numbering of putative membrane-spanning regions corresponds to those of B.

Tissue Localization of AQP9-- High stringency Northern analysis revealed a strong 1.5-kb transcript in liver (Fig. 2A). Signals of 2.2 kb were detected in testis and brain, suggesting alternative splicing or use of different polyadenylation sites. No hybridization signals were detected in kidney, colon, heart, and skeletal muscle. Nonradioactive in situ hybridization in rat liver showed that AQP9 is expressed evenly among hepatocytes (Fig. 2B). In testis, AQP9 mRNA was detected in the inner surface of seminiferous tubules and in the interstitial Leydig cells. In seminiferous tubules, signals were obtained in spermatocytes at early developmental stages but not at later stages and not in Sertoli cells. AQP9 mRNA was detected in astrocytes throughout the brain (data not shown).

View larger version (65K): [in this window] [in a new window]   Fig. 2.   Tissue localization of AQP9-mRNA. A, Northern blot analysis from various rat tissues. B, AQP9 mRNA in rat liver and testis detected by in situ hybridization. Bright field micrographs of cryosections hybridized to digoxigenin-labeled AQP9 antisense cRNA probe are shown. Upper panel, cross-section of liver (CV, central vein). AQP9 mRNA was found in hepatocytes (arrows). Hybridization of sense AQP9 cRNA probe did not reveal any signal (data not shown). Lower panel, cross-section of testis. Asterisks indicate the lumen of the seminiferous tubules, containing mature spermatocytes with long tails. AQP9 mRNA was detected selectively in immature spermatocytes (large arrows) and also in the interstitial Leydig cells (small arrows). Bar = 100 µm.

Functional Expression in Xenopus Oocytes-- When expressed in cRNA-injected oocytes, AQP9 increased the urea permeability coefficient (P_s) from 1.5 × 10⁶ ± 0.2 × 10⁶ cm/s (water-injected) to 23.5 × 10⁶ ± 2.0 × 10⁶ cm/s (Fig. 3A). The increase in P_s was similar to that observed in oocytes expressing the urea transporters UT2 and UT3 (P_s = 25-45 × 10⁶ cm/s) (cf. Refs. 4, 10, and 18). The activation energy estimated from Arrhenius plots was 7.8 ± 1.5 kcal/mol, consistent with movement through a pore. We then determined the selectivity of the AQP9 pore (Fig. 3A) and obtained P_s values for polyols (glycerol, mannitol, and sorbitol), purines (adenine), pyrimidines (uracil and the chemotherapeutic agent 5-fluorouracil), and urea analogues (thiourea) ranging from 15 to 25 × 10⁶ cm/s, suggesting a promiscuous permselectivity profile for AQP9. Radiotracer uptake studies revealed that AQP9 was impermeable to cyclic sugars (D-glucose, D-mannose, and myo-inositol), the nucleoside uridine, and amino acids (glutamine and glycine) (data not shown).

View larger version (36K): [in this window] [in a new window]   Fig. 3.   Functional properties of AQP9 expressed in Xenopus oocytes. A, solute permeability in oocytes expressing AQP9. Uptake of 1 mM 14C- or 3H-labeled carbamides, polyols, purines, pyrimidines, nucleosides, and monocarboxylates was measured over 90 s in oocytes injected with water (control) or AQP9 cRNA. Measurements were performed at 22 °C except for lactate uptakes which were performed at 4 °C to minimize thecontribution from endogenous lactate transport (29). 5-FU, 5-fluorouracil; -HB, -hydroxybutyrate. Data are mean ± S.E. from 6 to 8 oocytes. B, pH-dependent monocarboxylate permeation. Uptake of 1 mM 14C-labeled lactate and -hydroxybutyrate was measured at physiological pH (Barth's solution pH 7.3-7.5) and at pH 5.5. The increase in permeability was obtained as the ratio of the uptake at pH 5.5 to the uptake at 7.3-7.5. C, solute permeability in oocytes expressing AQP1 and AQP3. Uptake of 1 mM radiolabeled solute was measured under identical experimental conditions as in A with oocytes expressing AQP1 or AQP3. D, the osmotic water permeability (Pf) was measured in oocytes expressing AQP1, AQP3, or AQP9. Where indicated, oocytes were preincubated in the presence of either 0.1 mM phloretin (10 min) or 0.3 mM HgCl2 (5 min) and during uptake. The reversal of mercurial inhibition was studied by incubation with 5 mM -mercaptoethanol for 15 min following 10 min of treatment with 0.3 mM HgCl2. Data represent the mean ± S.E. from 6 to 8 oocytes. E, macroscopic ionic conductance in oocytes expressing AQP9 and AQP1 under initial conditions and after 15 min superfusing with 10 µM forskolin. Data are mean ± S.E. from 5 oocytes in each group. F, inhibition of water and solute permeability by phloretin and HgCl2. Percent inhibition of water and solute permeability was examined by incubation with 0.1 mM (or 0.5 mM) phloretin or 0.3 mM HgCl2, for 10 and 5 min, respectively. Asterisks indicate no significant difference from zero (t test).

To investigate the effect of electric charge on solute permeability, we tested uptake of the monocarboxylates lactate and -hydroxybutyrate, each of physiological importance in hepatocytes. Their P_s values were significantly increased at physiological pH, but an additional 4-fold increase was observed at pH 5.5 (Fig. 3B), whereas mannitol uptake was independent of pH. In voltage-clamped oocytes expressing AQP9, monocarboxylates at concentrations up to 10 mM evoked no significant currents (less than 5 nA), regardless of pH_o. Together with pH dependence of radiotracer uptakes, these results indicate that monocarboxylates permeate AQP9 only in their protonated form. The low permeabilities of the purine analogues xanthine and uric acid at pH 7.4 suggest that, likewise, these compounds permeate AQP9 in their protonated form (Fig. 3A).

We measured radiotracer uptake in oocytes expressing the aquaporins AQP1 and AQP3 to compare their solute permeabilities with those of AQP9 (Fig. 3C). AQP1 did not mediate significant uptake of any solute tested, indicating that AQP1 is a selective water channel (1-3). AQP3 facilitated glycerol uptake at levels similar to that for AQP9, but a weak urea permeability was detected in AQP3 (25% of the P_s value for AQP9). In addition, AQP3 was impermeable to the urea analogue thiourea, to polyols larger than glycerol, and to purines and pyrimidines. Our results suggest that the pore selectivity in the aquaporins decreases in the order AQP1 > AQP3 > AQP9. The osmotic permeability coefficient P_f was increased 30-fold (to 0.014 ± 0.0013 cm/s) in oocytes expressing AQP9 (cf. 0.0005 ± 0.00002 cm/s in water-injected oocytes) (Fig. 3D). AQP9 showed a P_f similar to that for AQP1 (0.016 ± 0.0014 cm/s), but AQP3 exhibited a lower P_f (0.0073 ± 0.0008 cm/s). The Arrhenius activation energy for AQP9-mediated P_f was 3.6 ± 1.3 kcal/mol, again consistent with movement through a pore (1-3).

Notably, unlike other known aquaporins, water permeability was sensitive to 0.1 mM phloretin (86% inhibition). In AQP9, P_f was reduced 61% in the presence of 0.3 mM HgCl₂. A cysteine residue thought to be involved in mercurial binding lies 3 amino acid residues N-terminal to the second NPA box (1-3). Thus, AQP9 possesses general features of water channels in addition to the distinctive phloretin-inhibitable permeability for a large variety of non-charged solutes.

Ion Conductance of AQP9-- It has been generally considered that none of the aquaporins mediates any type of ion conductance under normal conditions (1-3). A recent report (19) suggested that forskolin induced a nonspecific cation conductance via AQP1, despite the absence of a typical consensus protein kinase A phosphorylation site. This phenomenon has been disputed by others (20) applying the same protocols. By using voltage-clamped oocytes expressing either AQP1 or AQP9, we determined the macroscopic conductance from the slope of the linear current-voltage relationship (between +50 mV and 150 mV) before and after superfusion with 10 µM forskolin in Barth's solution for 15 min (Fig. 3E). Only low ionic conductance was observed in the presence and absence of forskolin, in oocytes expressing AQP1 or AQP9, and in water-injected oocytes. The reversal potential was unchanged in all groups following forskolin treatment. Forskolin administered by direct microinjection into the oocytes was also ineffective (not shown). Therefore, neither AQP1 nor AQP9 mediates any ionic conductance under basal or forskolin-treated conditions.

Inhibition Profiles of AQP9-- A fundamental question is whether or not solutes and water share a single pore in AQP9. To address this issue, we first examined the inhibition profiles of solute permeabilities by phloretin and mercurial compounds. Phloretin (0.1 mM) and HgCl₂ (0.3 mM) effectively inhibited the water permeability as well as the permeabilities for mannitol, uracil, adenine, and -hydroxybutyrate (75-90%) (Fig. 3F). Glycerol and urea permeabilities were inhibited 35-45% by 0.1 mM phloretin. Glycerol permeability was inhibited 50% by 0.3 mM HgCl₂, but urea permeability was not significantly affected by HgCl₂. In oocytes expressing AQP3, water and urea permeabilities were partially inhibited by 0.1 mM phloretin and 0.3 mM HgCl₂ (15-20%), whereas the glycerol permeability was unchanged. The similar inhibition profiles of solute and water permeabilites in AQP9 indicate that solutes and water share a common transmembrane pathway.

Determination of Reflection Coefficients-- This common pathway was further investigated by volumetric assays under iso-osmotic conditions as well as by mathematical simulation of water and solute flows. Oocytes expressing AQP9 were transferred from standard Barth's solution into Barth's solution containing test solute (176 mosm). In AQP9 expressing oocytes, rapid swelling was observed for mannitol and glycerol (Fig. 4A), whereas in AQP3 expressing oocytes, rapid swelling was observed only for glycerol (Fig. 4B). When the test solute was replaced by water (hypo-osmotic solution), oocytes expressing AQP9 exhibited the same rapid swelling as for test solutes, suggesting that there is no discrimination between permeable solutes and water.

View larger version (22K): [in this window] [in a new window]   Fig. 4.   Hypo- and iso-osmotic responses in oocytes expressing AQP9, AQP1, and AQP3. Time course of osmotic swelling of oocytes expressing AQP9 (A) and AQP3 (B). Data are the mean from triplicate trials. C, determination of Staverman's reflection coefficient () in oocytes expressing AQP9, AQP1, and AQP3. DMT, 1,3-dimethylthiourea. Data are mean ± S.E. from 4 to 7 oocytes. , AQP1; , AQP9; , AQP3. D, osmotic lysis assays of oocytes expressing AQP9. A range of solutes was examined by observing osmotic lysis of oocytes under the microscope 10 min after applying modified Barth's solution as described in A. The radius (nm) of each substrate was estimated from the molecular weight (Mr) and density () (26); r = (Mr/ × 1/ × 3/4)1/3; +, oocytes lysed; , oocytes showed no volume changes; n, number of oocytes; n.a., data not available.

The Staverman's reflection coefficient () which is an indicator of the efficacy of a solute to induce osmosis was determined by simulation of solute and water movement (Fig. 4, A and B) using the Kedem and Katchalsky equations (Equations 1 and 2) for volume flow (J_v) and solute flux (J_s) (21, 22),

(Eq. 1)

(Eq. 2)

in which P_f is the osmotic water permeability coefficient; P_s is the diffusive solute permeability coefficient; A is the membrane area (0.045 cm²); V_w is the molar volume of water (18 cm³/mol);  is the reflection coefficient of the test solute; and C_i = ([Na⁺]_in + [Cl]_in)  ([Na⁺]_out + [Cl]_out); _p = ([test solute]_in + [test solute]_out)/2; and c_p = [test solute]_in  [test solute]_out. A  value near unity indicates that the solute elicits the full osmotic pressure, whereas a  value near zero indicates that the solute induces a negligible osmotic pressure. The former is indicative of distinct pathways and the latter of a common pathway for water and solute.

Mathematical simulation (23) according to the above equations, using P_f values from hypotonic swelling experiments (Fig. 3D) and P_s values from tracer uptake studies (Fig. 3A), revealed  values that were close to zero. (We did not use P_s values from iso-osmotic assays (Fig. 4) because they are valid only when J_v  J_s (24).) Most of the permeable solutes gave  values near zero (Fig. 4C). In contrast, oocytes expressing AQP3 gave  values close to unity for polyols larger than glycerol (mannitol, threitol, and erythritol) and were close to zero only for small polyols (glycerol and 1,3-propanediol). In experiments with AQP1,  was 1 for all solutes tested. These data substantiate our claim that AQP9 has a common pathway for structurally unrelated neutral solutes and water.

To define the selectivity of AQP9 in further detail, experiments were performed using an osmotic lysis approach (Fig. 4D), in which solutes (176 mosm) were tested for their ability to induce osmotic lysis under iso-osmotic conditions in oocytes expressing AQP9. Osmotic lysis was induced by xylitol, erythritol, 1,3-propanediol, dimethylthiourea, and acetamide but not by raffinose, sucrose, methyl-D-glucopyranoside, glucose 6-phosphate, glycerol 3-phosphate, sodium or potassium gluconate, KCl, and choline chloride. To test the possibility that AQP9 is a rectifying solute channel, oocytes expressing AQP9 were exposed to hypertonic Barth's solutions containing 1.0 M mannitol or 1.0 M NaCl. NaCl induced shrinkage, whereas mannitol did not (data not shown), supporting the concept that AQP9 is a symmetrical channel.

The discovery of AQP9 may now highlight the roles that members of the aquaporin family could play in rapid movement of solutes across cell membranes with minimal osmotic perturbation, particularly in tissues that accumulate high levels of metabolites. The liver is a major site of urea production, and a rapid urea exit mechanism is required, and the lack of specialized urea transporters and selective functional water channels in hepatocytes (1-3, 10) emphasizes the need of these cells for AQP9 as an indiscriminate channel. In addition to urea, AQP9 may provide an exit route for purines and pyrimidines derived from nucleotide synthesis de novo, ensuring the plentiful supply of nucleotides to the brain, muscle, and hematopoietic tissues, in which only a salvage pathway is available (25). Purine and pyrimidine analogues such as 5-fluorouracil and 6-mercaptopurine are commonly used as chemotherapeutic agents. AQP9 may indirectly affect the chemosensitivity and resistance to these agents in cancer tissues. Permeation of monocarboxylates such as lactate and -hydroxybutyrate is necessary because liver is a major site of lactate utilization and ketone body formation (5). Hepatocytes secrete lactate under hypoxic conditions and export a large amount of ketone bodies such as -hydroxybutyrate and acetoacetate induced by fasting or diabetic conditions. Notably, AQP9 mRNA was up-regulated in liver from streptozotocin-induced diabetic rats.²

In summary, we report the first characterization of a broad selectivity, neutral solute channel, AQP9, that permits solutes to cross cell membranes rapidly and with minimal osmotic perturbation. The observations from inhibition studies (Fig. 3F), and oocyte swelling assays (Fig. 4A), as well as the reflection coefficients (Fig. 4C) strongly indicate that AQP9 provides a common transmembrane pathway for both solutes and water. Our findings have significant physiological implications, particularly in cells that require absorption and excretion of large amounts of metabolites. AQP9's indiscriminate nature, which allows passage of a wide range of structurally unrelated solutes, highlights its pharmacological relevance and the need for structural studies (27, 28) to elucidate the molecular design of this unique promiscuous pore.

	FOOTNOTES

^* This work was supported in part by National Institutes of Health Grants DK46289 (to M. A. H.) and DK32753 (to W. B. G.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank^TM/EMBL Data Bank with accession number(s) AF016406.

Supported by a Research Fellowship of the National Kidney Foundation.

^§ Supported by the Siriraj-China Medical Board, Mahidol University, Thailand.

^¶ Samuel A. Levine Fellow of the American Heart Association, Massachusetts Affiliate.

Supported by National Institutes of Health Grant DK38452 (to Dr. Dennis Brown).

^§§ To whom correspondence should be addressed: Renal Division, Brigham & Women's Hospital, 77 Ave. Louis Pasteur, Boston MA 02115. Tel.: 617-525-5820; Fax: 617-525-5830; E-mail: mhediger{at}rics.bwh.harvard.edu.

The abbreviations used are: AQP, aquaporin; UT, urea transporter; kb, kilobase pairs.

² H. Tsukaguchi and M. A. Hediger, unpublished data.

	REFERENCES

Top Abstract Introduction Materials & Methods Results & Discussion References

1. Verkman, A. S., Shi, L.-B., Frigeri, A., Hasegawa, H., Farinas, J., Mitra, A., Skach, W., Brown, D., van Hoek, A. N., and Ma, T. (1995) Kidney Int. 48, 1069-1081[Medline] [Order article via Infotrieve]
2. Agre, P., Brown, D., and Nielsen, S. (1995) Curr. Opin. Cell Biol. 7, 472-483[CrossRef][Medline] [Order article via Infotrieve]
3. Knepper, M. A., Wade, J. B., Terris, J., Ecelbarger, C. A., Marples, D., Mandon, B., Chou, C. L., Kishore, B. K., and Nielsen, S. (1996) Kidney Int. 49, 1712-1717[Medline] [Order article via Infotrieve]
4. You, G., Smith, C. P., Kanai, Y., Lee, W.-S., Stelzner, M., and Hediger, M. A. (1993) Nature 365, 844-847[CrossRef][Medline] [Order article via Infotrieve]
5. Erlinger, S. (1994) in The Liver: Biology and Pathobiology (Arias, I. M., Boyer, J. L., Fausto, N., Jacoby, W. B., Schachter, D. A., and Shafritz, D. A., eds), 3rd Ed., pp. 769-786, Raven Press, Ltd., New York
6. Strange, K. (1992) J. Am. Soc. Nephrol. 3, 12-27[Abstract]
7. Hasegawa, H., and Verkman, A. S. (1993) Am. J. Physiol. 265, C514-C520[Abstract/Free Full Text]
8. Effros, R. M., Jacobs, E., Hacker, A., Ozker, K., and Murphy, C. (1993) J. Clin. Invest. 91, 2822-2828
9. vom Dahl, S., and Haussinger, D. (1996) J. Biol Chem. 377, 25-37
10. Tsukaguchi, H., Shayakul, C., Berger, U. V., Tokui, T., Brown, D., and Hediger, M. A. (1997) J. Clin. Invest. 99, 1506-1515[Medline] [Order article via Infotrieve]
11. Echevarria, M., Windhager, E. E., Tate, S. S., and Frindt, G. (1994) Proc. Natl. Acad. Sci. U. S. A. 91, 10997-11001[Abstract/Free Full Text]
12. Preston, G. M., Carroll, T. P., Guggino, W. B., and Agre, P. (1992) Science 256, 385-387[Abstract/Free Full Text]
13. Ishibashi, K., Sasaki, S., Fushimi, K., Uchida, S., Kuwahara, M., Saito, H., Furukawa, T., Nakajima, K., Yamaguchi, Y., Gojobori, T., and Marumo, F. (1994) Proc. Natl. Acad. Sci. U. S. A. 91, 6269-6273[Abstract/Free Full Text]
14. Ma, T., Frigeri, A., Hasegawa, H., and Verkman, A. S. (1994) J. Biol. Chem. 269, 21845-21849[Abstract/Free Full Text]
15. Ishibashi, K., Kuwahara, M., Gu, Y., Kageyama, Y., Tohsaka, A., Suzuki, F., Marumo, F., and Sasaki, S. (1997) J. Biol. Chem. 272, 20782-20786[Abstract/Free Full Text]
16. Maurel, C., Reizer, J., Schroeder, J. I., and Chrispeels, M. J. (1993) EMBO J. 12, 2241-2247[Medline] [Order article via Infotrieve]
17. Ishibashi, K., Kuwahara, M., Gu, Y., Tanaka, Y., Marumo, F., and Sasaki, S. (1998) Biochem. Biophys. Res. Commun. 244, 268-274[CrossRef][Medline] [Order article via Infotrieve]
18. Smith, C. P., Lee, W.-S., Martial, S., You, G., Sands, J. M., and Hediger, M. A. (1995) J. Clin. Invest. 96, 1556-1563
19. Yool, A. J., Stamer, W. D., and Regan, J. W. (1996) Science 273, 1216-1218[Abstract]
20. Agre, P., Lee, M. D., Devidas, S., Guggino, W. B., Sasaki, S., Uchida, S., Kuwahara, M., Fushimi, K., Marumo, F., Verkman, A. S., Yang, B., Deen, P. M. T., Mulders, S. M., Kansen, S. M., van Os, C. H., Fischbarg, J., Kuang, K., Li, J., Iserovich, P., Wen, Q., Patil, R. V., Han, Z., and Wax, M. B. (1997) Science 275, 1490-1492[Free Full Text]
21. Kedem, O., and Katchalsky, A. (1958) Biochim. Biophys. Acta 27, 229-246[Medline] [Order article via Infotrieve]
22. Mannuzzu, L. M., Moronne, M. M., and Macey, R. I. (1993) J. Member. Biol. 133, 85-97[Medline] [Order article via Infotrieve]
23. Fairness, J., Simanek, V., and Vermin, A. S. (1995) Biopsy. J. 68, 1613-1620
24. Verkman, A. S., Dix, J. A., and Seifter, J. L. (1985) Am. J. Physical. 248, F650-F655
25. Che, M., Gatmaitan, Z., and Arias, I. M. (1997) FASEB J. 11, 101-108[Abstract]
26. Lide, D. R. (ed) (1997) Handbook of Chemistry and Physics, 78th Ed., CRC Press, Inc., Boca Raton, FL
27. Walz, T., Hirai, T., Murata, K., Heymann, J. B., Mitsuoka, K., Fujiyoshi, Y., Smith, B. L., Agre, P., and Engel, A. (1997) Nature 387, 624-627[CrossRef][Medline] [Order article via Infotrieve]
28. Cheng, A., van Hoek, A. N., Yeager, M., Verkman, A. S., and Mitra, A. S. (1997) Nature 387, 627-630[CrossRef][Medline] [Order article via Infotrieve]
29. Garcia, C. K., Brown, M. S., Pathak, R. K., and Goldstein, G. L. (1995) J. Biol. Chem. 270, 1843-1849[Abstract/Free Full Text]
30. Romero, M. F., Kanai, Y., Gunshin, H., and Hediger, M. A. (1998) Methods Enzymol. 296

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