TRPV4 in porcine lens epithelium regulates hemichannel-mediated ATP release and Na-K-ATPase activity

In several tissues, transient receptor potential vanilloid 4 (TRPV4) channels are involved in the response to hyposmotic challenge. Here we report TRPV4 protein in porcine lens epithelium and show that TRPV4 activation is an important step in the response of the lens to hyposmotic stress. Hyposmotic solution (200 mosM) elicited ATP release from intact lenses and TRPV4 antagonists HC 067047 and RN 1734 prevented the release. In isosmotic solution, the TRPV4 agonist GSK1016790A (GSK) elicited ATP release. When propidium iodide (PI) (MW 668) was present in the bathing medium, GSK and hyposmotic solution both increased PI entry into the epithelium of intact lenses. Increased PI uptake and ATP release in response to GSK and hyposmotic solution were abolished by a mixture of agents that block connexin and pannexin hemichannels, 18α-glycyrrhetinic acid and probenecid. Increased Na-K-ATPase activity occurred in the epithelium of lenses exposed to GSK and 18α-glycyrrhetinic acid + probenecid prevented the response. Hyposmotic solution caused activation of Src family kinase and increased Na-K-ATPase activity in the lens epithelium and TRPV4 antagonists prevented the response. Ionomycin, which is known to increase cytoplasmic calcium, elicited ATP release, the magnitude of which was no greater when lenses were exposed simultaneously to ionomycin and hyposmotic solution. Ionomycin-induced ATP release was significantly reduced in calcium-free medium. TRPV4-mediated calcium entry was examined in Fura-2-loaded cultured lens epithelium. Hyposmotic solution and GSK both increased cytoplasmic calcium that was prevented by TRPV4 antagonists. The cytoplasmic calcium rise in response to hyposmotic solution or GSK was abolished when calcium was removed from the bathing solution. The findings are consistent with hyposmotic shock-induced TRPV4 channel activation which triggers hemichannel-mediated ATP release. The results point to TRPV4-mediated calcium entry that causes a cytoplasmic calcium increase which is an essential early step in the mechanism used by the lens to sense and respond to hyposmotic stress.

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TRPV4 in Porcine Lens Epithelium Regulates Hyposmotic Stress‐Induced ATP Release and Na, K‐ATPase Activity

The FASEB Journal ◽

10.1096/fasebj.26.1_supplement.1064.4 ◽

2012 ◽

Vol 26 (S1) ◽

Author(s):

Mohammad Shahidullah ◽

Amritlal Mandal ◽

Nicholas A Delamere

Keyword(s):

Atpase Activity ◽

Atp Release ◽

Lens Epithelium ◽

Hyposmotic Stress

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Hyposmotic stress causes ATP release and stimulates Na,K-ATPase activity in porcine lens

Journal of Cellular Physiology ◽

10.1002/jcp.22858 ◽

2012 ◽

Vol 227 (4) ◽

pp. 1428-1437 ◽

Cited By ~ 29

Author(s):

M. Shahidullah ◽

A. Mandal ◽

C. Beimgraben ◽

N.A. Delamere

Keyword(s):

Atpase Activity ◽

Atp Release ◽

Hyposmotic Stress

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Dynamic regulation of extracellular ATP in Escherichia coli

Biochemical Journal ◽

10.1042/bcj20160879 ◽

2017 ◽

Vol 474 (8) ◽

pp. 1395-1416 ◽

Cited By ~ 7

Author(s):

Cora Lilia Alvarez ◽

Gerardo Corradi ◽

Natalia Lauri ◽

Irene Marginedas-Freixa ◽

María Florencia Leal Denis ◽

...

Keyword(s):

Escherichia Coli ◽

Atpase Activity ◽

Atp Release ◽

Membrane Vesicles ◽

Fold Increase ◽

Extracellular Atp ◽

Outer Membrane Vesicles ◽

Dynamic Regulation ◽

E Coli

We studied the kinetics of extracellular ATP (ATPe) in Escherichia coli and their outer membrane vesicles (OMVs) stimulated with amphipatic peptides melittin (MEL) and mastoparan 7 (MST7). Real-time luminometry was used to measure ATPe kinetics, ATP release, and ATPase activity. The latter was also determined by following [32P]Pi released from [γ-32P]ATP. E. coli was studied alone, co-incubated with Caco-2 cells, or in rat jejunum segments. In E. coli, the addition of [γ-32P]ATP led to the uptake and subsequent hydrolysis of ATPe. Exposure to peptides caused an acute 3-fold (MST7) and 7-fold (MEL) increase in [ATPe]. In OMVs, ATPase activity increased linearly with [ATPe] (0.1–1 µM). Exposure to MST7 and MEL enhanced ATP release by 3–7 fold, with similar kinetics to that of bacteria. In Caco-2 cells, the addition of ATP to the apical domain led to a steep [ATPe] increase to a maximum, with subsequent ATPase activity. The addition of bacterial suspensions led to a 6–7 fold increase in [ATPe], followed by an acute decrease. In perfused jejunum segments, exposure to E. coli increased luminal ATP 2 fold. ATPe regulation of E. coli depends on the balance between ATPase activity and ATP release. This balance can be altered by OMVs, which display their own capacity to regulate ATPe. E. coli can activate ATP release from Caco-2 cells and intestinal segments, a response which in vivo might lead to intestinal release of ATP from the gut lumen.

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Involvement of VNUT-exocytosis in transient receptor potential vanilloid 4-dependent ATP release from gastrointestinal epithelium

PLoS ONE ◽

10.1371/journal.pone.0206276 ◽

2018 ◽

Vol 13 (10) ◽

pp. e0206276 ◽

Cited By ~ 7

Author(s):

Hiroshi Mihara ◽

Kunitoshi Uchida ◽

Schuichi Koizumi ◽

Yoshinori Moriyama

Keyword(s):

Transient Receptor Potential ◽

Atp Release ◽

Receptor Potential ◽

Transient Receptor Potential Vanilloid ◽

Gastrointestinal Epithelium ◽

Transient Receptor

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Hyposmotic Stress‐induced Cytoplasmic Calcium Increase Involves TRPV4 and Src Family Kinase Activation

The FASEB Journal ◽

10.1096/fasebj.26.1_supplement.1064.3 ◽

2012 ◽

Vol 26 (S1) ◽

Author(s):

Amritlal Mandal ◽

Mohammad Shahidullah ◽

Nicholas A Delamere

Keyword(s):

Cytoplasmic Calcium ◽

Src Family Kinase ◽

Kinase Activation ◽

Hyposmotic Stress

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The Sensitivity of the Pedal Ganglion of the Slug to Osmotic Pressure Changes

Journal of Experimental Biology ◽

10.1242/jeb.33.3.493 ◽

1956 ◽

Vol 33 (3) ◽

pp. 493-501

Author(s):

G. A. KERKUT ◽

B. J. R. TAYLOR

Keyword(s):

Osmotic Pressure ◽

Ionic Concentration ◽

The Body ◽

Bathing Solution ◽

Pedal Ganglion ◽

Bathing Medium ◽

Rates Of Change ◽

Fluid Concentration ◽

Locke Solution ◽

Pressure Changes

1. The effects of different dilutions of Locke solution on the electrical activity of the isolated pedal ganglion of the slug can be reproduced by adding different concentrations of glucose of mannitol to a given concentration of Locke. 2. This indicates that certain cells in the pedal ganglion are sensitive to the osmotic pressure of the solution and not its ionic concentration. 3. The preparation is sensitive to slow changes in the concentration of the bathing medium. The cells increased their activity when the bathing solution was slowly changed from 0.7 Locke to 0.6 Locke, the change taking 43 min. This corresponds approximately to a change of 1% of the body fluid concentration over 4 min. Such rates of change are found in the normal intact animal. 4. The sensitivity of the preparation compares well with that of the mammalian osmoreceptors.

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Recovery of Transmembrane Potentials in Plants Resistant to Aryloxyphenoxypropanoate Herbicides: A Phenomenon Awaiting Explanation

Weed Science ◽

10.1017/s0043174500080413 ◽

1994 ◽

Vol 42 (2) ◽

pp. 293-301 ◽

Cited By ~ 21

Author(s):

Joseph A. M. Holtum ◽

Rainer E. Häusler ◽

Malcolm D. Devine ◽

Stephen B. Powles

Keyword(s):

Plasma Membrane ◽

Single Gene ◽

Membrane Vesicles ◽

Bathing Solution ◽

Root Tips ◽

Plasma Membrane Vesicles ◽

Bathing Medium ◽

Transmembrane Potentials ◽

Wild Oats ◽

Rigid Ryegrass

Aryloxyphenoxypropanoate (APP) herbicides, such as diclofop, depolarize membranes in parenchyma cells of coleoptiles and root tips, and isolated tonoplast or plasma membrane vesicles from a variety of plant species. Some APP-resistant biotypes of rigid ryegrass and wild oat repolarize membranes after removal of herbicide from a bathing medium. The repolarization ability does not require presence of either APP-insensitive acetyl coenzyme A carboxylase or an increased capacity for herbicide detoxification. The kinetics of depolarization and repolarization depend upon the herbicide, the herbicide concentration, the biotype, and the pH of the bathing solution. For rigid ryegrass, depolarization in the presence of diclofop acid is more rapid than in the presence of diclofop-methyl, and 50% depolarization required about 4 μM diclofop acid. Both the nonherbicidal S(–) and the herbicidal R(+) enantiomers of diclofop acid depolarized membranes in susceptible and resistant ryegrass. Susceptible biotypes regenerated transmembrane potentials following removal of the S(–) but not the R(+) enantiomer, whereas resistant biotypes repolarized following exposure to either enantiomer or a mixture of the two. The herbicide 2,4-D affected, in a complex manner, the ability of both susceptible and resistant ryegrass biotypes to depolarize and repolarize. It is postulated that the intracellular concentration of diclofop acid in susceptible and resistant plants is not the same due to differences in the partitioning of diclofop acid between the extracellular spaces and the cytoplasm. The mechanism producing the postulated difference is unknown, but observations on the proton extrusion capacity of both ryegrass and wild oats, the responses of ryegrass to [K+] and PCMBS, and the single-gene inheritance pattern of resistance in wild oats indicate that changes in the diclofop sensitivity of a plasma membrane protein involved in the generation of proton or ion gradients may be involved.

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