Aquaporin homologues in plants and mammals transport ammonia

Jahn, Thomas P.; Møller, Anders Hauer; Zeuthen, Thomas; Holm, Lars; Klærke, Dan A.; Mohsin, Brigitte; Kühlbrandt, Werner; Schjøerring, Jan K.

doi:10.1016/j.febslet.2004.08.004

Cited by 310 publications

(255 citation statements)

References 35 publications

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“…That the ar/R region is the key determinant of whether NH 3 or urea are conducted in SoPIP2;1 coincides with mutational results (see below) and former work, in which residues in the ar/R region were involved in the ammonia [1] or urea conductance [7] in plant aquaporin homologs.…”

Section: Simulation Of Small Solute Conduction In a Plant Aquaporinsupporting

confidence: 85%

Molecular determinants of ammonia and urea conductance in plant aquaporin homologs

et al. 2008

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Aquaporins and/or aquaglyceroporins regulate the permeability of plant membranes to water and small, uncharged molecules. Using molecular simulations with a plant plasma membrane aquaporin tetramer, the residues in the channel constriction region were identified as the crucial determinants of ammonia and urea conductance. The impact of these residues was experimentally verified using AtPIP2;1 pore mutants. Several, but not all, mutants with a NIP-like selectivity filter promoted yeast growth on urea or ammonia as sole sources of nitrogen. TIP-like mutants conducted urea but not NH 3 , and a residue without direct contact to the pore lumen was critical for conduction in the mutants.

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Section: Simulation Of Small Solute Conduction In a Plant Aquaporinsupporting

confidence: 85%

Molecular determinants of ammonia and urea conductance in plant aquaporin homologs

et al. 2008

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“…Substitutions within this region have been shown to be at least in part responsible for the substrate specificity in a number of aquaporins (45)(46)(47). Interestingly hAQP8, AtTIP1;1, and AtTIP1;2 share three substitutions in this critical region (F58H, H182I, and C191G), suggesting that indeed these substitutions may classify a new subgroup of H 2 O 2 -channeling aquaporins.…”

Section: Discussionmentioning

confidence: 98%

“…However, TIP2;1 possesses the same substitutions as hAQP8 but failed to increase sensitivity of yeast on medium containing H 2 O 2 (data not shown). TIP2;1 is known to be functionally expressed at the yeast plasma membrane (45). Therefore, additional structural features must be important for diffusion of H 2 O 2 through aquaporins.…”

Section: Discussionmentioning

confidence: 99%

Specific Aquaporins Facilitate the Diffusion of Hydrogen Peroxide across Membranes

Bienert

Møller

Kristiansen

et al. 2007

Journal of Biological Chemistry

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1,164

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The metabolism of aerobic organisms continuously produces reactive oxygen species. Although potentially toxic, these compounds also function in signaling. One important feature of signaling compounds is their ability to move between different compartments, e.g. to cross membranes. Here we present evidence that aquaporins can channel hydrogen peroxide (H 2 O 2 ). Twenty-four aquaporins from plants and mammals were screened in five yeast strains differing in sensitivity toward oxidative stress. Expression of human AQP8 and plant Arabidopsis TIP1;1 and TIP1;2 in yeast decreased growth and survival in the presence of H 2 O 2 . Further evidence for aquaporin-mediated H 2 O 2 diffusion was obtained by a fluorescence assay with intact yeast cells using an intracellular reactive oxygen species-sensitive fluorescent dye. Application of silver ions (Ag ؉ ), which block aquaporin-mediated water diffusion in a fast kinetics swelling assay, also reversed both the aquaporindependent growth repression and the H 2 O 2 -induced fluorescence. Our results present the first molecular genetic evidence for the diffusion of H 2 O 2 through specific members of the aquaporin family.Hydrogen peroxide (H 2 O 2 ) 2 belongs to the group of reactive oxygen species (ROS). ROS are generated in a number of key metabolic processes in cells like the electron transport chain in the inner mitochondrial membrane (1) and, specific for plants, the chloroplast thylakoid membrane (2).Because ROS can potentially damage proteins, lipids, and nucleic acids, cells have a number of ROS-scavenging systems that are able to remove these molecules and to maintain a relatively low and constant ROS concentration (3). However, ROS are also intermediates in various signal transduction pathways and have been shown to initiate responses to various stresses and disorders (for recent reviews, see Refs. 4 and 5). Arabidopsis mutants lacking an NADPH oxidase were not able to respond adequately to potassium deficiency (6) and were impaired in stomatal closure (7), providing genetic evidence for a role of NADPH oxidase in signaling.ROS are interconvertible molecules including singlet oxygen, superoxide, hydroxyl radical, and H 2 O 2 . H 2 O 2 has a distinctive set of features compared with other ROS. (i) It is not charged, (ii) it is not a radical, (iii) it possesses an intermediate oxidation number, (iv) it is relatively stable under physiological conditions, and (v) catalase can disproportionate it into water and molecular oxygen without the expense of reduction equivalents.Although substantial progress has been made regarding the formation and scavenging of ROS, little is known about their transport from the site of origin to the place of action or detoxification. Recently three studies from mammalian systems have provided evidence that H 2 O 2 , in addition to the well studied role in intracellular signaling, is also used as an intercellular signal molecule (8 -10). This implies that a necessary step within these signal transduction pathways is the transport of H 2 O 2 ...

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“…12,[38][39][40] In addition, several metabolically important small neutral solutes and ions have been identified as AQP substrates, namely hydrogen peroxide (H 2 O 2 ). 13,17,41,42 carbon dioxide, 43,44 nitric oxide, 45,46 ammonia, 47,48 metalloids such as arsenite and antimonite, 49-51 selenite, 52 boric acid, 53 and silicic acid. 51 AQP6 with low intrinsic water permeability may function primarily as an anion transporter.…”

Section: Aqp Permeability To Small Solutesmentioning

confidence: 99%

Role of aquaporins in cell proliferation: What else beyond water permeability?

2016

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In addition to the extensive data demonstrating the importance of mammalian AQPs for the movement of water and some small solutes across the cell membrane, there is now a growing body of evidence indicating the involvement of these proteins in numerous cellular processes seemingly unrelated, at least some of them in a direct way, to their canonical function of water permeation. Here, we have presented a broad range of evidence demonstrating that these proteins have a role in cell proliferation by various different mechanisms, namely, by allowing fast cell volume regulation during cell division; by affecting progression of cell cycle and helping maintain the balance between proliferation and apoptosis, and by crosstalk with other cell membrane proteins or transcription factors that, in turn, modulate progression of the cell cycle or regulate biosynthesis pathways of cell structural components. In the end, however, after discussing all these data that strongly support a role for AQPs in the cell proliferation process, it remains impossible to conclude that all these other functions attributed to AQPs occur completely independently of their water permeability, and there is a need for new experiments designed specifically to address this interesting issue.

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Aquaporin homologues in plants and mammals transport ammonia

Abstract: Using functional complementation and a yeast mutant deficient in ammonium (NH þ 4 ) transport (Dmep1-3), three wheat (Triticum aestivum) TIP2 aquaporin homologues were isolated that restored the ability of the mutant to grow when 2 mM NH

Cited by 310 publications

References 35 publications

Molecular determinants of ammonia and urea conductance in plant aquaporin homologs

Molecular determinants of ammonia and urea conductance in plant aquaporin homologs

Specific Aquaporins Facilitate the Diffusion of Hydrogen Peroxide across Membranes

Role of aquaporins in cell proliferation: What else beyond water permeability?

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