Osmotic Swelling Activates two Pathways for K&lt;sup&gt;+&lt;/sup&gt; Efflux in a Rat Hepatoma Cell Line

Junankar, Pauline R.; Karjalainen, Ari; Kirk, Kiaran

doi:10.1159/000078106

Cited by 13 publications

(9 citation statements)

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“…It has also been proposed, again mostly on the basis of pharmacological inhibition, that a hyposmotic challenge induces the transport of taurine and K + (Rb + ) via a shared pathway in trout erythrocytes [107]. Cell-swelling stimulates taurine release and activates at least two K + (Rb + ) efflux pathways, one of which is blocked by barium, in rat hepatoma HTC cells [108]. The barium-insensitive moiety of volume-sensitive K + (Rb + ) efflux shares several characteristics with the taurine efflux component: both have similar time-courses and pharmacological profiles which has led to the suggestion that they share a common pathway [108].…”

Section: Does Cell Swelling Induce Taurine and K + Transport Via A Simentioning

confidence: 99%

“…Cell-swelling stimulates taurine release and activates at least two K + (Rb + ) efflux pathways, one of which is blocked by barium, in rat hepatoma HTC cells [108]. The barium-insensitive moiety of volume-sensitive K + (Rb + ) efflux shares several characteristics with the taurine efflux component: both have similar time-courses and pharmacological profiles which has led to the suggestion that they share a common pathway [108]. It has also been claimed that taurine and K + efflux from human erythroleukemia cells under hyposmotic conditions share a pathway for transport.…”

Section: Does Cell Swelling Induce Taurine and K + Transport Via A Simentioning

confidence: 99%

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Swelling-Induced Taurine Transport: Relationship with Chloride Channels, Anion-Exchangers and Other Swelling-Activated Transport Pathways

Shennan¹

2008

Cell Physiol Biochem

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Cells have to regulate their volume in order to survive. Moreover, it is now evident that cell volume per se and the membrane transport processes which regulate it, comprise an important signalling unit. For example, macromolecular synthesis, apoptosis, cell growth and hormone secretion are all influenced by the cellular hydration state. Therefore, a thorough understanding of volume-activated transport processes could lead to new strategies being developed to control the function and growth of both normal and cancerous cells. Cell swelling stimulates the release of ions such as K⁺ and Cl^- together with organic osmolytes, especially the β-amino acid taurine. Despite being the subject of intense research interest, the nature of the volume-activated taurine efflux pathway is still a matter of controversy. On the one hand it has been suggested that osmosensitive taurine efflux utilizes volume-sensitive anion channels whereas on the other it has been proposed that the band 3 anion-exchanger is a swelling-induced taurine efflux pathway. This article reviews the evidence for and against a role of anion channels and exchangers in osmosensitive taurine transport. Furthermore, the distinct possibility that neither pathway is involved in taurine transport is highlighted. The putative relationship between swelling-induced taurine transport and volume-activated anionic amino acid, α-neutral amino acid and K⁺ transport is also examined.

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Section: Does Cell Swelling Induce Taurine and K + Transport Via A Simentioning

confidence: 99%

Section: Does Cell Swelling Induce Taurine and K + Transport Via A Simentioning

confidence: 99%

Swelling-Induced Taurine Transport: Relationship with Chloride Channels, Anion-Exchangers and Other Swelling-Activated Transport Pathways

Shennan¹

2008

Cell Physiol Biochem

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“…Most recently, volumesensitive anion channels have been implicated in porcine sperm where RVD induced by an osmolality of 180 mmol/kg is inhibited by the chloride channel blockers NPPB (5-nitro-2(3-phenylpropylamino) benzoic acid), tamoxifen and DIDS (diisothiocyanatostilbene-2,2 0 -disulfonic acid) (Petrunkina et al, 2004b). There is evidence in various somatic cell types that different magnitudes of osmolality challenge invoke different pathways or efflux of different osmolytes in volume regulation (Kinne, 1998;MacLeod and Hamilton, 1999a,b;Junankar et al, 2004;Ordaz et al, 2004). In the present study, changes in osmolality mimicking physiological conditions were employed to study RVDC in addition to K þ channels.…”

Section: Introductionmentioning

confidence: 99%

The role of anion channels and Ca²⁺ in addition to K⁺ channels in the physiological volume regulation of murine spermatozoa

Yeung

Barfield

Cooper

2005

Molecular Reproduction Devel

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Studies in the human, transgenic mice, and cattle indicate that sperm cell volume regulation plays an important role in male fertility as spermatozoa encounter a hypo-osmotic challenge upon ejaculation into the female tract. Physiological regulatory volume decrease (RVD) was examined using flow cytometry in murine sperm released into incubation medium mimicking uterine osmolality and including putative channel inhibitors. The involvement of K+ channels was indicated by the recovery of volume regulation by the K+ ionophore valinomycin in defective sperm from infertile transgenic mice, and from blockage of RVD by quinine in normal sperm. However, in neither case was the recovery complete. The involvement of volume-sensitive osmolyte and anion channels (VSOAC) were investigated using blockers effective in other cell types. NPPB (5-nitro-2(3-phenylpropylamino) benzoic acid) and tamoxifen inhibited RVD but SITS (4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulphonic acid) at 0.4 and 1 mM had no effect whereas DIDS (di-isothiocyanato-stilbene-2,2'-disulphonic acid) at 1 mM enhanced RVD. Verapamil, but not another P-glycoprotein antagonist cyclosporin, caused sperm swelling which persisted in the presence of valinomycin, in Ca2+-free medium and in the presence of thapsigargin, but swelling was abolished by the Ca2+ ionophore A23187. Nifedipine was slightly effective in blocking RVD. Analysis by Western blotting failed to reveal ClC-2 and ClC-3 members of the chloride channel family in murine or rat sperm proteins despite signal bands in positive tissue controls. These findings implicate the involvement of some unidentified VSOAC in sperm volume regulation, which is probably Ca+-dependent.

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“…This would support a potential role for SK channels in hepatocellular volume regulation. On the other hand, alanine uptake, which elicits hepatocellular swelling, has been shown to evoke the opening of 30 -90 pS K ϩ channels (15), and the IK channel blocker clotrimazole, but not the SK channel blocker apamin, attenuates hepatocellular swelling-induced K ϩ efflux (16). These findings support a potential role for IK channels in hepatocellular volume regulation.…”

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confidence: 71%

Ca2+-activated IK1 Channels Associate with Lipid Rafts upon Cell Swelling and Mediate Volume Recovery

Barfod

Moore

Roe

et al. 2007

Journal of Biological Chemistry

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Restoration of cell volume in the continued presence of osmotic stimuli is essential, particularly in hepatocytes, which swell upon nutrient uptake. Responses to swelling involve the Ca 2؉ -dependent activation of K ؉ channels, which promote fluid efflux to drive volume recovery; however, the channels involved in hepatocellular volume regulation have not been identified. We found that hypotonic exposure of HTC hepatoma cells evoked the opening of 50 pS K ؉ -permeable channels, consistent with intermediate conductance (IK) channels. We isolated from rat liver and HTC cells a cDNA with sequence identity to the coding region of IK1. Swelling-activated currents were inhibited by transfection with a dominant interfering IK1 mutant. The IK channel blockers clotrimazole and TRAM-34 inhibited whole cell swelling-activated K ؉ currents and volume recovery. To determine whether IK1 underwent volume-sensitive localization, we expressed a green fluorescent protein fusion of IK1 in HTC cells. The localization of IK1 was suggestive of distribution in lipid rafts. Consistent with this, there was a time-dependent increase in colocalization between IK1 and the lipid raft ganglioside GM1 on the plasma membrane, which subsequently decreased with volume recovery. Pharmacological disruption of lipid rafts altered the plasma membrane distribution of IK1 and inhibited volume recovery after hypotonic exposure. Collectively, these findings support the hypothesis that IK1 regulates compensatory responses to hepatocellular swelling and suggest that regulation of cell volume involves coordination of signaling from lipid rafts with IK1 function.As a metabolically active organ, the liver is subjected to physiological stimuli that elicit dynamic alterations in cell volume. For example, after meals, hepatocytes swell as a consequence of Na ϩ -coupled amino acid uptake and insulin-stimulated changes in cation permeability (1, 3 and large conductance (BK) K ϩ channels, and consistent with this, IK, SK, and BK channel genes have been found to be expressed in these tissues (9 -12). We and others have shown functional evidence of 10 pS Ca 2ϩ -activated K ϩ channels and expression of the SK isoforms SK2 and SK3 in hepatocytes (9,13,14). This would support a potential role for SK channels in hepatocellular volume regulation. On the other hand, alanine uptake, which elicits hepatocellular swelling, has been shown to evoke the opening of 30 -90 pS K ϩ channels (15), and the IK channel blocker clotrimazole, but not the SK channel blocker apamin, attenuates hepatocellular swelling-induced K ϩ efflux (16). These findings support a potential role for IK channels in hepatocellular volume regulation. Others have reported that alanine evokes the opening of BK (200 pS) channels in hepatocytes (17). In liver, immunolabeling studies have suggested that IK1 protein (also known as SK4, KCa3.1, and KCNN4) is predominantly expressed in bile duct epithelia (18); however, volume recovery has been found to be predominantly mediated by SK2 channels in those cells (9). I...

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Osmotic Swelling Activates two Pathways for K<sup>+</sup> Efflux in a Rat Hepatoma Cell Line

Cited by 13 publications

References 49 publications

Swelling-Induced Taurine Transport: Relationship with Chloride Channels, Anion-Exchangers and Other Swelling-Activated Transport Pathways

Swelling-Induced Taurine Transport: Relationship with Chloride Channels, Anion-Exchangers and Other Swelling-Activated Transport Pathways

The role of anion channels and Ca²⁺ in addition to K⁺ channels in the physiological volume regulation of murine spermatozoa

Ca2+-activated IK1 Channels Associate with Lipid Rafts upon Cell Swelling and Mediate Volume Recovery

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Osmotic Swelling Activates two Pathways for K<sup>+</sup> Efflux in a Rat Hepatoma Cell Line

Cited by 13 publications

References 49 publications

Swelling-Induced Taurine Transport: Relationship with Chloride Channels, Anion-Exchangers and Other Swelling-Activated Transport Pathways

Swelling-Induced Taurine Transport: Relationship with Chloride Channels, Anion-Exchangers and Other Swelling-Activated Transport Pathways

The role of anion channels and Ca2+ in addition to K+ channels in the physiological volume regulation of murine spermatozoa

Ca2+-activated IK1 Channels Associate with Lipid Rafts upon Cell Swelling and Mediate Volume Recovery

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The role of anion channels and Ca²⁺ in addition to K⁺ channels in the physiological volume regulation of murine spermatozoa