Mercury-Sensitive Residues and Pore Site in AQP3 Water Channel

Kuwahara, Michio; Gu, Yong; Ishibashi, Keiichiro; Marumo, Fumiaki; Sasaki, Sei

doi:10.1021/bi9711442

Cited by 95 publications

(67 citation statements)

References 18 publications

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“…However, it was not possible to reverse this effect by mercaptoethanol treatment. This is in contrast to the observations of human AQP3 and AQP10, where at 1·mmol·l -1 HgCl2 there is significant inhibition of water transport, which is partially reversed in the presence of mercaptoethanol (Ishibashi et al, 2002;Kuwahara et al, 1997b).…”

Section: Cloning Of Cdna and Amino Acid Sequence Analysiscontrasting

confidence: 99%

Isolation of a novel aquaglyceroporin from a marine teleost (Sparus auratus): function and tissue distribution

Santos

Estêvão

Fuentes

et al. 2004

Journal of Experimental Biology

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SUMMARYThe aquaporins (formerly called the major intrinsic protein family) are transmembrane channel proteins. The family includes the CHIP group, which are functionally characterised as water channels and the GLP group, which are specialised for glycerol transport. The present study reports the identification and characterisation of a novel GLP family member in a teleost fish, the sea bream Sparus auratus. A sea bream aquaporin (sbAQP)cDNA of 1047 bp and encoding a protein of 298 amino acids was isolated from a kidney cDNA library. Functional characterization of the sbAQP using a Xenopus oocyte assay revealed that the isolated cDNA stimulated osmotic water permeability in a mercury-sensitive manner and also stimulated urea and glycerol uptake. Northern blotting demonstrated that sbAQP was expressed at high levels in the posterior region of the gut, where two transcripts were identified (1.6 kb and 2 kb), and in kidney, where a single transcript was present (2 kb). In situ hybridisation studies with a sbAQP riboprobe revealed its presence in the lamina propria and smooth muscle layer of the posterior region of the gut and in epithelial cells of some kidney tubules. sbAQP was also present in putative chloride cells of the gill. Phylogenetic analysis of sbAQP, including putative GLP genes from Fugu rubripes, revealed that it did not group with any of the previously isolated vertebrate GLPs and instead formed a separate group, suggesting that it may be a novel GLP member.

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Section: Cloning Of Cdna and Amino Acid Sequence Analysiscontrasting

confidence: 99%

Isolation of a novel aquaglyceroporin from a marine teleost (Sparus auratus): function and tissue distribution

Santos

Estêvão

Fuentes

et al. 2004

Journal of Experimental Biology

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“…Mercury affects AQPs by acting on cysteine residues of the water channels. The mercury-sensitive cysteine in AQP3, Cys 11 , is located in the NH 2 -terminal part of the protein (23). Thus, mercury has to penetrate the cell membrane to reach its target, which makes the mercury effect relatively slow.…”

Section: Discussionmentioning

confidence: 99%

Copper Inhibits the Water and Glycerol Permeability of Aquaporin-3

Zelenina

Tritto

Bondar

et al. 2004

Journal of Biological Chemistry

123

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Aquaporin-3 (AQP3) is an aquaglyceroporin expressed in erythrocytes and several other tissues. Erythrocytes are, together with kidney and liver, the main targets for copper toxicity. Here we report that both water and glycerol permeability of human AQP3 is inhibited by copper. Inhibition is fast, dose-dependent, and reversible. If copper is dissolved in carbonic acid-bicarbonate buffer, the natural buffer system in our body, doses in the range of those observed in Wilson disease and in copper poisoning caused significant inhibition. AQP7, another aquaglyceroporin, was insensitive to copper. Copper is an essential trace element in the human body. It is present in the blood and is incorporated in several vital proteins, such as Cu,Zn-SOD, dopamine ␤-hydroxylase, ceruloplasmin, cytochrome c oxidase, etc. (recently reviewed in Ref. 1). Blood levels of copper are increased in several pathological conditions, such as Wilson disease, Indian childhood cirrhosis, juvenile rheumatoid arthritis, thalassemia, and sickle cell anemia (1-5).Aquaporin-3 (AQP3) 1 is an aquaglyceroporin expressed in several mammalian tissues including erythrocytes (6 -12). It is well established that erythrocytes are permeable for glycerol, but the molecular mechanism for this effect is still obscure. It is also well established that glycerol permeability of erythrocytes is extremely sensitive to copper. We have recently shown that AQP3 water permeability is sensitive to nickel (13). Here we report that copper is a potent inhibitor of AQP3 permeability for glycerol and water. We expressed AQP3 in a human cell line and tested the effect of copper on glycerol and water permeability of the transfected cells. Three extracellular amino acid residues were found to be responsible for the copper sensitivity. We modeled the situation when AQP3 is co-expressed with another AQP, not permeable for glycerol, and found that only glycerol but not water permeability will be inhibited by copper in such cells. The results of this study provide a better understanding of processes that occur in severe copper metabolism defects and copper poisoning. MATERIALS AND METHODScDNA Constructs-The constructs for expression of human AQP3 (wild type and mutants) and the long form of AQP4 have been described previously (13). cDNA fragments encoding full-length AQP3 and AQP4 were obtained by amplification from the human lung QUICK-Clone cDNA library (Clontech). cDNA encoding mouse AQP7 was a kind gift from J. M. Carbrey and P. Agre (Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD). The cDNA fragments were subcloned in-frame into the pEGFP-N2 vector for AQP3 tagged with green fluorescent protein (GFP) at the COOH terminus into pIRES2-EGFP vector (Clontech) for AQP3 and GFP expressed in the same cell as separate proteins and into the pEGFP-C2 vector for AQP4 and AQP7 tagged with GFP at NH 2 termini. The point mutations in extracellular loops of human AQP3 were generated by PCR-based mutagenesis using wild-type cDNA as a template and c...

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“…AQP3 is a relatively weak transporter of water but functions as an efficient glycerol transporter (4). Reflection coefficient measurements (5) and mutagenesis studies (6) suggested that water and glycerol share a common pathway through the AQP3 protein, although inhibition experiments were interpreted as suggesting different pathways (7). Immunocytochemistry in rat showed AQP3 protein expression in basolateral membrane of kidney collecting duct and large airways, as well as in several tissues that are thought not to have an important water-transporting role including urinary bladder, conjunctiva, and epidermis (8)(9)(10)(11).…”

mentioning

confidence: 99%

Nephrogenic diabetes insipidus in mice lacking aquaporin-3 water channels

Song

Yang

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

363

251

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Aquaporin-3 (AQP3) is a water channel expressed at the basolateral plasma membrane of kidney collecting-duct epithelial cells. The mouse AQP3 cDNA was isolated and encodes a 292-amino acid water͞glycerol-transporting glycoprotein expressed in kidney, large airways, eye, urinary bladder, skin, and gastrointestinal tract. The mouse AQP3 gene was analyzed, and AQP3 null mice were generated by targeted gene disruption. The growth and phenotype of AQP3 null mice were grossly normal except for polyuria. AQP3 deletion had little effect on AQP1 or AQP4 protein expression but decreased AQP2 protein expression particularly in renal cortex. Fluid consumption in AQP3 null mice was more than 10-fold greater than that in wild-type litter mates, and urine osmolality (<275 milliosmol) was much lower than in wild-type mice (>1,200 milliosmol). After 1-desamino-8-D-arginine-vasopressin administration or water deprivation, the AQP3 null mice were able to concentrate their urine partially to Ϸ30% of that in wild-type mice. Osmotic water permeability of cortical collecting-duct basolateral membrane, measured by a spatial filtering optics method, was >3-fold reduced by AQP3 deletion. To test the hypothesis that the residual concentrating ability of AQP3 null mice was due to the inner medullary collecting-duct water channel AQP4, AQP3͞AQP4 double-knockout mice were generated. The double-knockout mice had greater impairment of urinary-concentrating ability than did the AQP3 single-knockout mice. Our findings establish a form of nephrogenic diabetes insipidus produced by impaired water permeability in collecting-duct basolateral membrane. Basolateral membrane aquaporins may thus provide blood-accessible targets for drug discovery of aquaretic inhibitors.water transport ͉ AQP3 ͉ kidney ͉ urinary-concentrating mechanism ͉ polyuria A quaporin-3 (AQP3, originally called glycerol intrinsic protein, GLIP, based on its glycerol-transport function) was cloned from rat kidney by our laboratory (1) as well as by Ishibashi et al. (2) and Echevarria et al. (3). AQP3 is a relatively weak transporter of water but functions as an efficient glycerol transporter (4). Reflection coefficient measurements (5) and mutagenesis studies (6) suggested that water and glycerol share a common pathway through the AQP3 protein, although inhibition experiments were interpreted as suggesting different pathways (7). Immunocytochemistry in rat showed AQP3 protein expression in basolateral membrane of kidney collecting duct and large airways, as well as in several tissues that are thought not to have an important water-transporting role including urinary bladder, conjunctiva, and epidermis (8-11). Recent studies report strong AQP3 expression in various regions of the gastrointestinal tract including small intestine (12). Another unique feature of AQP3 is its gene structure, which is different from the water-selective mammalian aquaporins (13). AQP3, AQP7, and AQP9 have been called ''aquaglyceroporins'' because of their relatively broad solute specificity and sequence ho...

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Mercury-Sensitive Residues and Pore Site in AQP3 Water Channel

Cited by 95 publications

References 18 publications

Isolation of a novel aquaglyceroporin from a marine teleost (Sparus auratus): function and tissue distribution

Isolation of a novel aquaglyceroporin from a marine teleost (Sparus auratus): function and tissue distribution

Copper Inhibits the Water and Glycerol Permeability of Aquaporin-3

Nephrogenic diabetes insipidus in mice lacking aquaporin-3 water channels

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