scholarly journals Relative CO2/NH3 selectivities of mammalian aquaporins 0–9

2013 ◽  
Vol 304 (10) ◽  
pp. C985-C994 ◽  
Author(s):  
R. Ryan Geyer ◽  
Raif Musa-Aziz ◽  
Xue Qin ◽  
Walter F. Boron
Keyword(s):  
Plasma Membrane ◽  
Water Permeability ◽  
Xenopus Oocytes ◽  
Video Microscopy ◽  
Osmotic Water Permeability ◽  
Permeability Ratio ◽  
Diverse Range ◽  
Surface Ph ◽  
Aquaporin 1 ◽  
Osmotic Water

Previous work showed that aquaporin 1 (AQP1), AQP4-M23, and AQP5 each has a characteristic CO2/NH3 and CO2/H2O permeability ratio. The goal of the present study is to characterize AQPs 0–9, which traffic to the plasma membrane when heterologously expressed in Xenopus oocytes. We use video microscopy to compute osmotic water permeability ( Pf) and microelectrodes to record transient changes in surface pH (ΔpHS) caused by CO2 or NH3 influx. Subtracting respective values for day-matched, H2O-injected control oocytes yields the channel-specific values Pf* and ΔpHS*. We find that Pf* is significantly >0 for all AQPs tested except AQP6. (ΔpHS*)CO2 is significantly >0 for AQP0, AQP1, AQP4-M23, AQP5, AQP6, and AQP9. (ΔpHS*)NH3 is >0 for AQP1, AQP3, AQP6, AQP7, AQP8, and AQP9. The ratio (ΔpHS*)CO2/ Pf* falls in the sequence AQP6 (∞) > AQP5 > AQP4-M23 > AQP0 ≅ AQP1 ≅ AQP9 > others (0). The ratio (ΔpHS*)NH3/ Pf* falls in the sequence AQP6 (∞) > AQP3 ≅ AQP7 ≅ AQP8 ≅ AQP9 > AQP1 > others (0). Finally, the ratio (ΔpHS*)CO2/(−ΔpHS*)NH3 falls in the sequence AQP0 (∞) ≅ AQP4-M23 ≅ AQP5 > AQP6 > AQP1 > AQP9 > AQP3 (0) ≅ AQP7 ≅ AQP8. The ratio (ΔpHS*)CO2/(−ΔpHS*)NH3 is indeterminate for both AQP2 and AQP4-M1. In summary, we find that mammalian AQPs exhibit a diverse range of selectivities for CO2 vs. NH3 vs. H2O. As a consequence, by expressing specific combinations of AQPs, cells could exert considerable control over the movements of each of these three substances.

Expression of Aquaporin-1 in the Peritoneal Tissues: Localization and Regulation by Hyperosmolality

2002 ◽  
Vol 22 (3) ◽  
pp. 307-315 ◽  
Author(s):  
Tomoko Ota ◽  
Michio Kuwahara ◽  
Shuling Fan ◽  
Yoshio Terada ◽  
Takashi Akiba ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Water Permeability ◽  
Water Channel ◽  
Mesothelial Cells ◽  
Scattering Method ◽  
Osmotic Water Permeability ◽  
Peritoneal Mesothelial Cells ◽  
Aquaporin 1 ◽  
Osmotic Water ◽  
Aqp1 Expression

Objective The purpose of this study was to determine the localization of the aquaporin-1 (AQP1) water channel in peritoneal tissues and the effect of hyperosmolality on the peritoneal expression and function of AQP1. Methods Immunohistochemical localization of AQP1 was identified in rat peritoneal tissues. Cultured rat peritoneal mesothelial cells (RPMCs) were exposed to hyperosmolality by adding 4% glucose to the culture medium. After 1 hour, 4 hours, 24 hours, and 48 hours, AQP1 was identified by semiquantitative immunoblot and immunocytochemistry. Osmotic water permeability was measured using a light-scattering method. Results Immunohistochemistry of rat peritoneal tissues showed the presence of AQP1 in mesothelial cells, venular endothelial cells, and capillary endothelial cells, but not in arteriole and interstitial cells. Semiquantitative immunoblot revealed that exposure to hyperosmolality significantly increased AQP1 expression after 24 hours in whole RPMC lysates (3.3-fold at 24 hours and 3.9-fold at 48 hours). Consistent with the immunoblot, osmotic water permeability of RPMC was augmented 1.7-fold and 2.7-fold after 1 hour and 24 hours, respectively, in a hyperosmotic environment. In RPMC membrane fractions, AQP1 expression was significantly increased after 1 hour of exposure to hyperosmolality (3.9-fold at 1 hour, 7.1-fold at 4 hours, and 8.7-fold at 24 hours). Immunocytochemistry of RPMCs showed that AQP1 was gradually redistributed from the perinuclear area to the peripheral cytoplasm, and then to the plasma membrane after a 1-hour hyperosmotic challenge, suggesting hyperosmolality-induced translocation of AQP1. Upregulation of AQP1 was also observed in the omentum of rats loaded intraperitoneally with hyperosmotic dialysate every day for 10 weeks. Conclusion AQP1 is widely distributed in the peritoneal cavity and may provide the major aqueous pathway across the peritoneal barrier. In addition, our findings suggested that hyperosmolality increases AQP1-dependent water permeability in peritoneal tissues by regulating the translocation and synthesis of AQP1 protein.

Acetazolamide inhibits osmotic water permeability by interaction with aquaporin-1

2006 ◽  
Vol 350 (2) ◽  
pp. 165-170 ◽  
Author(s):  
Junwei Gao ◽  
Xiaohua Wang ◽  
Yongjie Chang ◽  
Jianzhao Zhang ◽  
Qianliu Song ◽  
...  
Keyword(s):  
Water Permeability ◽  
Osmotic Water Permeability ◽  
Aquaporin 1 ◽  
Osmotic Water

scholarly journals Metformin, an AMPK activator, stimulates the phosphorylation of aquaporin 2 and urea transporter A1 in inner medullary collecting ducts

2016 ◽  
Vol 310 (10) ◽  
pp. F1008-F1012 ◽  
Author(s):  
Janet D. Klein ◽  
Yanhua Wang ◽  
Mitsi A. Blount ◽  
Patrick A. Molina ◽  
Lauren M. LaRocque ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Water Permeability ◽  
Therapeutic Option ◽  
Apical Plasma Membrane ◽  
Osmotic Water Permeability ◽  
Urea Transporter ◽  
Aquaporin 2 ◽  
Urea Permeability ◽  
Osmotic Water ◽  
Collecting Ducts

Nephrogenic diabetes insipidus (NDI) is characterized by production of very large quantities of dilute urine due to an inability of the kidney to respond to vasopressin. Congenital NDI results from mutations in the type 2 vasopressin receptor (V2R) in ∼90% of families. These patients do not have mutations in aquaporin-2 (AQP2) or urea transporter UT-A1 (UT-A1). We tested adenosine monophosphate kinase (AMPK) since it is known to phosphorylate another vasopressin-sensitive transporter, NKCC2 (Na-K-2Cl cotransporter). We found AMPK expressed in rat inner medulla (IM). AMPK directly phosphorylated AQP2 and UT-A1 in vitro. Metformin, an AMPK activator, increased phosphorylation of both AQP2 and UT-A1 in rat inner medullary collecting ducts (IMCDs). Metformin increased the apical plasma membrane accumulation of AQP2, but not UT-A1, in rat IM. Metformin increased both osmotic water permeability and urea permeability in perfused rat terminal IMCDs. These findings suggest that metformin increases osmotic water permeability by increasing AQP2 accumulation in the apical plasma membrane but increases urea permeability by activating UT-A1 already present in the membrane. Lastly, metformin increased urine osmolality in mice lacking a V2R, a mouse model of congenital NDI. We conclude that AMPK activation by metformin mimics many of the mechanisms by which vasopressin increases urine-concentrating ability. These findings suggest that metformin may be a novel therapeutic option for congenital NDI due to V2R mutations.

scholarly journals Dynamic Changes in the Osmotic Water Permeability of Protoplast Plasma Membrane

2004 ◽  
Vol 135 (4) ◽  
pp. 2301-2317 ◽  
Author(s):  
Menachem Moshelion ◽  
Nava Moran ◽  
François Chaumont
Keyword(s):  
Plasma Membrane ◽  
Water Permeability ◽  
Osmotic Water Permeability ◽  
Dynamic Changes ◽  
Osmotic Water

scholarly journals Expression of multiple water channel activities in Xenopus oocytes injected with mRNA from rat kidney.

1993 ◽  
Vol 101 (6) ◽  
pp. 827-841 ◽  
Author(s):  
M Echevarria ◽  
G Frindt ◽  
G M Preston ◽  
S Milovanovic ◽  
P Agre ◽  
...  
Keyword(s):  
Water Permeability ◽  
Antisense Oligonucleotide ◽  
Xenopus Oocytes ◽  
Rat Kidney ◽  
Water Channel ◽  
Water Channels ◽  
Renal Tissue ◽  
Osmotic Water Permeability ◽  
Volume Increase ◽  
Osmotic Water

To test the hypothesis that renal tissue contains multiple distinct water channels, mRNA prepared from either cortex, medulla, or papilla of rat kidney was injected into Xenopus oocytes. The osmotic water permeability (Pf) of oocytes injected with either 50 nl of water or 50 nl of renal mRNA (1 microgram/microliter) was measured 4 d after the injection. Pf was calculated from the rate of volume increase on exposure to hyposmotic medium. Injection of each renal mRNA preparation increased the oocyte Pf. This expressed water permeability was inhibited by p-chloromercuriphenylsulfonate and had a low energy of activation, consistent with the expression of water channels. The coinjection of an antisense oligonucleotide for CHIP28 protein, at an assumed > 100-fold molar excess, with either cortex, medulla, or papilla mRNA reduced the expression of the water permeability by approximately 70, 100, and 30%, respectively. Exposure of the oocyte to cAMP for 1 h resulted in a further increase in Pf only in oocytes injected with medulla mRNA. This cAMP activation was not altered by the CHIP28 antisense oligonucleotide. These results suggest that multiple distinct water channels were expressed in oocytes injected with mRNA obtained from sections of rat kidney: (a) CHIP28 water channels in cortex and medulla, (b) cAMP-activated water channels in medulla, and (c) cAMP-insensitive water channels in papilla.

scholarly journals Role of multiple phosphorylation sites in the COOH-terminal tail of aquaporin-2 for water transport: evidence against channel gating

2009 ◽  
Vol 296 (3) ◽  
pp. F649-F657 ◽  
Author(s):  
Hanne B. Moeller ◽  
Nanna MacAulay ◽  
Mark A. Knepper ◽  
Robert A. Fenton
Keyword(s):  
Plasma Membrane ◽  
Water Transport ◽  
Water Permeability ◽  
Laser Scanning Microscopy ◽  
Apical Plasma Membrane ◽  
Phosphorylation Sites ◽  
Osmotic Water Permeability ◽  
Aquaporin 2 ◽  
Osmotic Water

Arginine vasopressin (AVP)-regulated phosphorylation of the water channel aquaporin-2 (AQP2) at serine 256 (S256) is essential for its accumulation in the apical plasma membrane of collecting duct principal cells. In this study, we examined the role of additional AVP-regulated phosphorylation sites in the COOH-terminal tail of AQP2 on protein function. When expressed in Xenopus laevis oocytes, prevention of AQP2 phosphorylation at S256A (S256A-AQP2) reduced osmotic water permeability threefold compared with wild-type (WT) AQP2-injected oocytes. In contrast, prevention of AQP2 single phosphorylation at S261 (S261A), S264 (S264A), and S269 (S269A), or all three sites in combination had no significant effect on water permeability. Similarly, oocytes expressing S264D-AQP2 and S269D-AQP2, mimicking AQP2 phosphorylated at these residues, had similar water permeabilities to WT-AQP2-expressing oocytes. The use of high-resolution confocal laser-scanning microscopy, as well as biochemical analysis demonstrated that all AQP2 mutants, with the exception of S256A-AQP2, had equal abundance in the oocyte plasma membrane. Correlation of osmotic water permeability relative to plasma membrane abundance demonstrated that lack of phosphorylation at S256, S261, S264, or S269 had no effect on AQP2 unit water transport. Similarly, no effect on AQP2 unit water transport was observed for the 264D and 269D forms, indicating that phosphorylation of the COOH-terminal tail of AQP2 is not involved in gating of the channel. The use of phosphospecific antibodies demonstrated that AQP2 S256 phosphorylation is not dependent on any of the other phosphorylation sites, whereas S264 and S269 phosphorylation depend on prior phosphorylation of S256. In contrast, AQP2 S261 phosphorylation is independent of the phosphorylation status of S256.

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