Characterization of Aquaporin-6 as a Nitrate Channel in Mammalian Cells

Ikeda, Masahiro; Beitz, Eric; Kozono, David; Guggino, William B.; Agre, Peter; Yasui, Masato

doi:10.1074/jbc.m207008200

Cited by 198 publications

(147 citation statements)

References 34 publications

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“…Besides water, aquaporins can also mediate the transport of nitrate, urea, glycerol, other polyols, and arsenic (Ma et al, 1997;Ikeda et al, 2002;Liu et al, 2002;Carbrey et al, 2003;Takata et al, 2004). HgCl 2 has a high affinity for inhibiting aquaporins via covalent modification of cysteine residues within the water pore and in other regions of the protein, causing either blockage or conformational changes to the protein leading to inhibition of water transport (Preston et al, 1993;Barone et al, 1998).…”

Section: Discussionmentioning

confidence: 99%

Physiological characteristics of selenite uptake by maize roots in response to different pH levels

Zhang

Shi

et al. 2010

Z. Pflanzenernähr. Bodenk.

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In selenite solutions, H 2 SeO 3 , HSeO À 3 , and SeO 2À 3 are in equilibrium in proportions that vary with solution pH. The physiological characteristics of selenite uptake were studied with excised roots of maize (Zea mays L.) seedlings at pH 3.0, 5.0, and 8.0. The results showed that 0.10 mM 2,4-dinitrophenol (DNP), 1.0 mM sodium fluoride (NaF), and a temperature of 4°C inhibited selenite uptake by maize roots by 16%, 20%, and 23% at pH 3.0, by up to 80%, 79%, and 78% at pH 5.0, and by 5%, 9%, and 16% at pH 8.0. Hence, selenite may enter roots at pH 5.0 in an energy-dependent manner, in contrast to pH 3.0 and 8.0. The uptake kinetics for selenite were determined for excised roots of maize, and the curves were linear at pH 3.0 and 8.0, but saturated at pH 5.0, showing that carrier-mediated uptake of selenite occurred at pH 5.0, but not at pH 3.0 or 8.0. Further studies showed that HgCl 2 and AgNO 3 inhibited selenite uptake separately by 81% and 76% at pH 3.0 and indicated that selenite was absorbed by maize roots through aquaporins at pH 3.0. At pH 8.0, anion-channel inhibitors only inhibited a small fraction of selenite uptake, indicating that the major absorption pathway of SeO 2À 3 species into roots was not absorbed passively through anion channels, but might involve other processes. According to these results, it is proposed that selenite uptake occurs via different mechanisms depending on its species in solution in response to pH levels.

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Section: Discussionmentioning

confidence: 99%

Physiological characteristics of selenite uptake by maize roots in response to different pH levels

Zhang

Shi

et al. 2010

Z. Pflanzenernähr. Bodenk.

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“…CCL-61) were transfected at 50 -60% confluence using Lipofectamine 2000 (Invitrogen) as described previously (13). Cultured cells on glass coverslips in 35-mm dishes were observed 24 h posttransfection using an FV-300 confocal microscope (Olympus, Japan).…”

Section: Methodsmentioning

confidence: 99%

The NPC Motif of Aquaporin-11, Unlike the NPA Motif of Known Aquaporins, Is Essential for Full Expression of Molecular Function

Ikeda¹,

Andoo²,

Shimono³

et al. 2011

Journal of Biological Chemistry

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The recently identified molecule aquaporin-11 (AQP11) has a unique amino acid sequence pattern that includes an AsnPro-Cys (NPC) motif, corresponding to the N-terminal AsnPro-Ala (NPA) signature motif of conventional AQPs. In this study, we examined the effect of the mutation of the NPC motif on the subcellular localization, oligomerization, and water permeability of AQP11 in transfected mammalian cells. Furthermore, the effect was also assessed using zebrafish. Sitedirected mutation at the NPC motif did not affect the subcellular localization of AQP11 but reduced its oligomerization. A cell swelling assay revealed that cells expressing AQP11 with a mutated NPC motif had significantly lower osmotic water permeability than cells expressing wild-type AQP11. Zebrafish deficient in endogenous AQP11 showed a deformity in the tail region at an early stage of development. This phenotype was dramatically rescued by injection of human wild-type AQP11 mRNA, whereas the effect of mRNA for AQP11 with a mutated NPC motif was less marked. Although the NPA motif is known to be important for formation of water-permeable pores by conventional AQPs, our observations suggest that the corresponding NPC motif of AQP11 is essential for full expression of molecular function.

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“…Aquaporins belong to a highly conserved group of membrane proteins called the major intrinsic proteins (MIPs) that are involved in the transport of water and small solutes such as glycerol, nitrate and urea [1,2].…”

Section: Introductionmentioning

confidence: 99%

Lack of Aquaporin 3 in bovine erythrocyte membranes correlates with low glycerol permeation

Campos

Moura

Oliva

et al. 2011

Biochemical and Biophysical Research Communications

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In general, erythrocytes are highly permeable to water, urea and glycerol.However, expression of aquaporin isoforms in erythrocytes appears to be species characteristic. In the present study, human (hRBC) and bovine (bRBC) erythrocytes were chosen for comparative studies due to their significant difference in membrane glycerol permeability.Osmotic water permeability (P f ) at 23 ºC was (2.89 0.37) 10 -2 and (5.12 0.61) 10 -2 cm s -1 for human and bovine cells respectively, with similar activation energies for water transport. Glycerol permeability (P gly ) for human ((1.37 0.26) 10 -5 cm s -1 ) differed in three orders of magnitude from bovine erythrocytes ((5.82 0.37) 10 -8 cm s -1 ) that also showed higher activation energy for glycerol transport.When compared to human, bovine erythrocytes showed a similar expression pattern of AQP1 glycosylated forms on immunoblot analysis, though in slight higher levels, which could be correlated with the 1.5-fold larger P f found. However, AQP3 expression was not detectable. Immunofluorescence analysis confirmed the absence of AQP3 expression in bovine erythrocyte membranes.In conclusion, lack of AQP3 in bovine erythrocytes points to the lipid pathway as responsible for glycerol permeation and explains the low glycerol permeability and high E a for transport observed in ruminants.

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Characterization of Aquaporin-6 as a Nitrate Channel in Mammalian Cells

Cited by 198 publications

References 34 publications

Physiological characteristics of selenite uptake by maize roots in response to different pH levels

Physiological characteristics of selenite uptake by maize roots in response to different pH levels

The NPC Motif of Aquaporin-11, Unlike the NPA Motif of Known Aquaporins, Is Essential for Full Expression of Molecular Function

Lack of Aquaporin 3 in bovine erythrocyte membranes correlates with low glycerol permeation

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