Caring about the other 47% of the water channels. Focus on “Basolateral targeting and microtubule-dependent transcytosis of the aquaporin-2 water channel”

2013 ◽  
Vol 304 (1) ◽  
pp. C33-C35 ◽  
Author(s):  
Curtis T. Okamoto
Keyword(s):  
Water Channel ◽  
Water Channels ◽  
The Other ◽  
Aquaporin 2 ◽  
Basolateral Targeting

Molecular physiology of urinary concentrating mechanism: regulation of aquaporin water channels by vasopressin

1997 ◽  
Vol 272 (1) ◽  
pp. F3-F12 ◽  
Author(s):  
M. A. Knepper
Keyword(s):  
Collecting Duct ◽  
Water Channel ◽  
Renal Medulla ◽  
Water Channels ◽  
Renal Physiology ◽  
Molecular Physiology ◽  
Water Excretion ◽  
Aquaporin 2 ◽  
New Research

The purpose of this review is to illustrate the application of molecular methodologies to the investigation of a fundamentally integrative problem in renal physiology, namely, the mechanism of regulation of water excretion by the kidney and the concomitant concentration of solutes in the urine. A new revolution in renal physiology is occurring as new research tools have become available as a result of the cloning of cDNAs for many of the major transporters and receptors in the renal medulla. Among the important renal medullary transporters are the aquaporin water channels, which mediate the osmotic water transport across renal medullary epithelia. One of these water channels, aquaporin-2, has been shown to be the target for short-term regulation of collecting duct water permeability by vasopressin. In addition, two collecting duct water channels, aquaporin-2 and aquaporin-3, are targets for long-term regulation by vasopressin through effects on the absolute expression levels of the water channel proteins. This review focuses on the mechanisms of both short- and long-term regulation of these water channels by vasopressin.

Radio and Electrical Measurements on Glacial Streams

1987 ◽  
Vol 33 (114) ◽  
pp. 239-242
Author(s):  
M. E. R. Walford
Keyword(s):  
Electrical Conductivity ◽  
Water Channel ◽  
Water System ◽  
Low Frequency ◽  
Water Channels ◽  
Radiative Loss ◽  
Radio Waves ◽  
Electrical Measurements ◽  
Water Conductivity ◽  
Glacier Surface

AbstractWe discuss the suggestion that small underwater transmitters might be used to illuminate the interior of major englacial water channels with radio waves. Once launched, the radio waves would naturally tend to be guided along the channels until attenuated by absorption and by radiative loss. Receivers placed within the channels or at the glacier surface could be used to detect the signals. They would provide valuable information about the connectivity of the water system. The electrical conductivity of the water is of crucial importance. A surface stream on Storglaciären, in Sweden, was found, using a low-frequency technique, to have a conductivity of approximately 4 × 10−4 S m−1. Although this is several hundred times higher than the conductivity of the surrounding glacier ice, the contrast is not sufficient to permit us simply to use electrical conductivity measurements to establish the connectivity of englacial water channels. However, the water conductivity is sufficiently small that, under favourable circumstances, radio signals should be detectable after travelling as much as a few hundred metres along an englacial water channel. In a preliminary field experiment, we demonstrated semi quantitatively that radio waves do indeed propagate as expected, at least in surface streams. We conclude that under-water radio transmitters could be of real practical value in the study of the englacial water system, provided that sufficiently robust devices can be constructed. In a subglacial channel, however, we expect the radio range would be much smaller, the environment much harsher, and the technique of less practical value.

Downregulation of renal vasopressin V2 receptor and aquaporin-2 expression parallels age-associated defects in urine concentration

2004 ◽  
Vol 287 (4) ◽  
pp. F797-F805 ◽  
Author(s):  
Ying Tian ◽  
Ryota Serino ◽  
Joseph G. Verbalis
Keyword(s):  
Collecting Duct ◽  
Water Channel ◽  
Age Groups ◽  
Urine Osmolality ◽  
Brown Norway ◽  
Water Restriction ◽  
Water Excretion ◽  
F1 Hybrid ◽  
Young Rats ◽  
Aquaporin 2

Renal concentrating ability is known to be impaired with aging. The antidiuretic hormone AVP plays an important role in renal water excretion by regulating the membrane insertion and abundance of the water channel aquaporin-2 (AQP2); this effect is primarily mediated via the V2 subtype of the AVP receptor (V2R). This study evaluated the hypothesis that decreased renal sensitivity to AVP, with subsequent altered renal AQP2 expression, contributes to the reduced urinary concentrating ability with aging. Our results show that under baseline conditions, urine osmolality is significantly lower in aged Fischer 344 and Brown-Norway F1 hybrid (F344BN) rats despite equivalent plasma AVP concentrations as in young rats. Levels of kidney V2R mRNA expression and AQP2 abundances were also significantly decreased in aged F344BN rats, as was AQP2 immunostaining in collecting duct cells. In response to moderate water restriction, urine osmolality increased by significantly lesser amounts in aged F344BN rats compared with young rats despite similar increases in plasma AVP levels. Moderate water restriction induced equivalent relative increases in renal AQP2 abundances in all age groups but resulted in significantly lower abundances in total kidney AQP2 protein in aged compared with young F344BN rats. These results therefore demonstrate a functional impairment of renal concentrating ability in aged F344BN rats that is not due to impaired secretion of AVP but rather appears to be related to impaired responsiveness of the kidney to AVP that is secondary, at least in part, to a downregulation of renal V2R expression and AQP2 abundance.

Water transport across mammalian cell membranes

1996 ◽  
Vol 270 (1) ◽  
pp. C12-C30 ◽  
Author(s):  
A. S. Verkman ◽  
A. N. van Hoek ◽  
T. Ma ◽  
A. Frigeri ◽  
W. R. Skach ◽  
...  
Keyword(s):  
Water Transport ◽  
Cell Membranes ◽  
Water Channel ◽  
Water Channels ◽  
Channel Structure ◽  
Level Information ◽  
Selective Channel ◽  
Transcriptional Units ◽  
Measurement Strategies

This review summarizes recent progress in water-transporting mechanisms across cell membranes. Modern biophysical concepts of water transport and new measurement strategies are evaluated. A family of water-transporting proteins (water channels, aquaporins) has been identified, consisting of small hydrophobic proteins expressed widely in epithelial and nonepithelial tissues. The functional properties, genetics, and cellular distributions of these proteins are summarized. The majority of molecular-level information about water-transporting mechanisms comes from studies on CHIP28, a 28-kDa glycoprotein that forms tetramers in membranes; each monomer contains six putative helical domains surrounding a central aqueous pathway and functions independently as a water-selective channel. Only mutations in the vasopressin-sensitive water channel have been shown to cause human disease (non-X-linked congenital nephrogenic diabetes insipidus); the physiological significance of other water channels remains unproven. One mercurial-insensitive water channel has been identified, which has the unique feature of multiple overlapping transcriptional units. Systems for expression of water channel proteins are described, including Xenopus oocytes, mammalian and insect cells, and bacteria. Further work should be directed at elucidation of the role of water channels in normal physiology and disease, molecular analysis of regulatory mechanisms, and water channel structure determination at atomic resolution.

Urinary excretion of the water channel aquaporin 2 correlated with the pharmacological effect of tolvaptan in cirrhotic patients with ascites

2015 ◽  
Vol 51 (6) ◽  
pp. 620-627 ◽  
Author(s):  
Hiroyuki Nakanishi ◽  
Masayuki Kurosaki ◽  
Takanori Hosokawa ◽  
Yuka Takahashi ◽  
Jun Itakura ◽  
...  
Keyword(s):  
Urinary Excretion ◽  
Water Channel ◽  
Pharmacological Effect ◽  
Aquaporin 2 ◽  
Cirrhotic Patients

Progesterone inhibition of water permeability in Bufo arenarum oocytes and urinary bladder

1996 ◽  
Vol 270 (5) ◽  
pp. F880-F885 ◽  
Author(s):  
P. Ford ◽  
G. Amodeo ◽  
C. Capurro ◽  
C. Ibarra ◽  
R. Dorr ◽  
...  
Keyword(s):  
Urinary Bladder ◽  
Xenopus Laevis ◽  
Water Permeability ◽  
Water Channel ◽  
Water Channels ◽  
Toad Urinary Bladder ◽  
Osmotic Permeability ◽  
Bufo Arenarum ◽  
Mrna Extraction

The ovarian oocytes from Bufo arenarum (BAO) but not those from Xenopus laevis (XLO) would have water channels (WC). We now report that the injection of the mRNA from BAO into the oocytes from XLO increased their water osmotic permeability (Pi) (reduced by 0.3 mM HgCl2 and reversed by 5 mM beta-mercaptoethanol). A 30-min challenge with progesterone induced, 18 h later, a reduction of the mercury-sensitive fraction of Pf in the BAO (but not in XLO). The mRNA from BAO pretreated with progesterone lost its capacity to induce WC in the XLO, but the hormone did not affect the expression of the WC in XLO previously injected with the mRNA from BAO. Pf was also measured in urinary bladders of BAO. Eighteen hours after a challenge with progesterone, a reduction in the hydrosmotic response to oxytocin was observed. Finally, the mRNA from the urinary bladder of BAO was injected into XLO. An increase in Pf was observed. This was not the case if, before the mRNA extraction, the bladders were treated with progesterone. We conclude that the BAO WC share progesterone sensitivity with the oxytocin-regulated water channel present in the toad urinary bladder.

scholarly journals Expression of VAMP-2-like protein in kidney collecting duct intracellular vesicles. Colocalization with Aquaporin-2 water channels.

1995 ◽  
Vol 96 (4) ◽  
pp. 1834-1844 ◽  
Author(s):  
S Nielsen ◽  
D Marples ◽  
H Birn ◽  
M Mohtashami ◽  
N O Dalby ◽  
...  
Keyword(s):  
Collecting Duct ◽  
Water Channels ◽  
Kidney Collecting Duct ◽  
Aquaporin 2 ◽  
Intracellular Vesicles

scholarly journals Reversed polarized delivery of an aquaporin-2 mutant causes dominant nephrogenic diabetes insipidus

2003 ◽  
Vol 163 (5) ◽  
pp. 1099-1109 ◽  
Author(s):  
Erik-Jan Kamsteeg ◽  
Daniel G. Bichet ◽  
Irene B.M. Konings ◽  
Hubert Nivet ◽  
Michelle Lonergan ◽  
...  
Keyword(s):  
Diabetes Insipidus ◽  
Water Conservation ◽  
Nephrogenic Diabetes Insipidus ◽  
Water Channel ◽  
Apical Plasma Membrane ◽  
Apical Surface ◽  
Aquaporin 2 ◽  
Frame Shift ◽  
Polarized Delivery ◽  
Mutant Forms

Vasopressin regulates body water conservation by redistributing aquaporin-2 (AQP2) water channels from intracellular vesicles to the apical surface of renal collecting ducts, resulting in water reabsorption from urine. Mutations in AQP2 cause autosomal nephrogenic diabetes insipidus (NDI), a disease characterized by the inability to concentrate urine. Here, we report a frame-shift mutation in AQP2 causing dominant NDI. This AQP2 mutant is a functional water channel when expressed in Xenopus oocytes. However, expressed in polarized renal cells, it is misrouted to the basolateral instead of apical plasma membrane. Additionally, this mutant forms heterotetramers with wild-type AQP2 and redirects this complex to the basolateral surface. The frame shift induces a change in the COOH terminus of AQP2, creating both a leucine- and a tyrosine-based motif, which cause the reversed sorting of AQP2. Our data reveal a novel cellular phenotype in dominant NDI and show that dominance of basolateral sorting motifs in a mutant subunit can be the molecular basis for disease.

Design Considerations for Artificial Water Channel–Based Membranes

2018 ◽  
Vol 48 (1) ◽  
pp. 57-82 ◽  
Author(s):  
Woochul Song ◽  
Chao Lang ◽  
Yue-xiao Shen ◽  
Manish Kumar
Keyword(s):  
Historical Perspective ◽  
Water Channel ◽  
Water Channels ◽  
Structure And Properties ◽  
High Permeability ◽  
Functional Elements ◽  
Design Considerations ◽  
Biological Water ◽  
Naturally Occurring ◽  
Artificial Water

Aquaporins (AQPs) are naturally occurring water channel proteins. They can facilitate water molecule translocation across cellular membranes with exceptional selectivity and high permeability that are unmatched in synthetic membrane systems. These unique properties of AQPs have led to their use as functional elements in membranes in recent years. However, the intricate nature of AQPs and concerns regarding their stability and processability have encouraged researchers to develop synthetic channels that mimic the structure and properties of AQPs and other biological water-conducting channels. These channels have been termed artificial water channels. This article reviews current progress and provides a historical perspective as well as an outlook toward developing scalable membranes based on artificial water channels.

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