Selection for MDR1/P-glycoprotein enhances swelling-activated K+ and Cl- currents in NIH/3T3 cells

Luckie, Douglas B.; Krouse, Mauri E.; Harper, K. L.; Law, T.; Wine, Jeffrey J.

doi:10.1152/ajpcell.1994.267.2.c650

Cited by 70 publications

(45 citation statements)

References 16 publications

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“…2 and 3). This result is in good agreement with an increasing number of recent papers, which report lack of correlation between P-gp expression and the magnitude of the volume-sensitive Cl Ϫ conductance (21)(22)(23)(24)(25). Also, in the present study four types of monoclonal antibodies directed against P-gp (C219, MRK16, MRK17, and UIC2) were all found to be ineffective in inhibiting the activity of the volume-sensitive Cl Ϫ channel in Intestine 407 cells (Figs.…”

Section: Absence Of Effect Of Activators Of Protein Kinase C On the Vsupporting

confidence: 91%

“…Subsequently, many laboratories have failed to find any correlation between the size of volume-sensitive Cl Ϫ currents and the P-gp expression level in multidrug-resistant or MDR1-transfected cells and their control counterparts (21)(22)(23)(24)(25). Moreover, volume-sensitive Cl Ϫ currents in many cell types have been found to be insensitive to blockers of P-gp-mediated drug transport (12, 22-24, 26, 27).…”

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confidence: 99%

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Volume-sensitive Chloride Channel Activity Does Not Depend on Endogenous P-glycoprotein

Tominaga

Miwa

et al. 1995

Journal of Biological Chemistry

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To determine whether endogenous P-glycoprotein, the MDR1 gene product that functions as a drug transport pump, is a volume-sensitive Cl ؊ channel molecule or a protein kinase C-mediated regulator of the Cl ؊ channel, whole-cell patch-clamp and molecular biological experiments were carried out in a human small intestinal epithelial cell line. Endogenous expression of P-glycoprotein was confirmed by Northern blot analysis, reverse transcription-polymerase chain reaction, Western blot analysis, and immunostaining. The P-glycoprotein expression was abolished by the antisense (but not sense) oligonucleotide for the MDR1 gene, whereas the magnitude of the Cl ؊ current activated by osmotic swelling was not distinguishable between both antisense-and sense-treated cells. The volume-sensitive Cl ؊ currents were not specifically affected by the anti-P-glycoprotein monoclonal antibodies, MRK16, C219, and UIC2. An inhibitor of P-glycoprotein-mediated pump activity, verapamil, was found to never affect the Cl ؊ current. A substrate for the P-glycoprotein-mediated drug pump, vincristine or daunomycin, did not prevent swelling-induced activation of the Cl ؊ current. Furthermore, the Cl ؊ current was not affected by an activator of protein kinase C (12-O-tetradecanoylphorbol-13-acetate or 1-oleoyl-2-acetyl-sn-glycerol). Thus, it is concluded that the endogenous P-glycoprotein molecule is not itself a volume-sensitive Cl ؊ channel nor a protein kinase C-mediated regulator of the channel in the human epithelial cells.Cell volume regulation is one of the most fundamental functions of living cells. A variety of ion channels and transporters are known to be activated upon osmotic cell swelling and involved in volume regulation (1-3). Among them, volume-sensitive Cl Ϫ channels have recently been studied in a variety of cell species (4 -16). However, the volume-sensitive Cl Ϫ channel molecule has not as yet been identified. P-glycoprotein, the MDR1 gene product, which is an ATPdependent transporter responsible for multidrug resistance to many anti-neoplastic agents (17), was recently proposed as a candidate molecule of the volume-sensitive Cl Ϫ channel (18, 19). Higgins and his collaborators (18) suggested that P-glycoprotein (P-gp) 1 is bifunctional, switching between a drug pump upon exposure to its substrates and a Cl Ϫ channel upon osmotic swelling, based on the following observations. 1) Volume-sensitive Cl Ϫ conductances correlated with P-gp expression induced by transfection with MDR1 (18); 2) inhibitors of the drug pump inhibited the volume-sensitive Cl Ϫ conductance (18, 20); 3) the volume-sensitive Cl Ϫ conductance was abolished by treatment with antisense oligonucleotides against the 5Ј-end of the MDR1 gene (18); and 4) intracellular administration of a substrate for the P-gp-mediated drug pump prevented swelling-induced activation of the Cl Ϫ conductance but failed to inhibit the preactivated volume-sensitive Cl Ϫ conductance (19,20).Subsequently, many laboratories have failed to find any correlation between the size of vol...

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Section: Absence Of Effect Of Activators Of Protein Kinase C On the Vsupporting

confidence: 91%

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confidence: 99%

Volume-sensitive Chloride Channel Activity Does Not Depend on Endogenous P-glycoprotein

Tominaga

Miwa

et al. 1995

Journal of Biological Chemistry

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“…Accordingly, it has been proposed that the putative relationship between Pgp and ICl,swell is due to the exposure to chemotherapeutic agents, and not to Pgp expression per se. By some unknown mechanism, the chemotherapeutic agents could alter the threshold for swelling activation of the Cl¦ current (Luckie et al 1994(Luckie et al , 1996. Our results indicate that C219 inhibits ICl,swell only in cells expressing Pgp, regardless of (a) origin of cDNA (human or hamster; Han et al 1996 and present results, respectively), (b) procedure employed to elicit Pgp expression, i.e.…”

Section: Inhibition Of Iclswell By C219 Requires Pgp Expressionmentioning

confidence: 53%

“…In addition, it has been proposed that the putative Pgp-ICl,swell relationship is due to alterations induced by cell exposure to chemotherapeutic agents, rather than to Pgp expression per se (Luckie et al 1994(Luckie et al , 1996. After the initial report that Pgp expression induced the appearance of ICl,swell (Valverde et al 1992), subsequent experiments showed that Pgp expression is not necessary for ICl,swell and does not augment it (e.g.…”

Section: Discussionmentioning

confidence: 99%

P‐glycoprotein is not a swelling‐activated Cl⁻ channel; possible role as a Cl⁻ channel regulator

Vanoye

Altenberg

Reuss

1997

The Journal of Physiology

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The whole‐cell configuration of the patch‐clamp technique was used to determine if P‐glycoprotein (Pgp) is a swelling‐activated Cl− channel. Hamster pgp1 cDNA was transfected into a mouse fibroblast cell line resulting in expression of functional Pgp in the plasma membrane. This cell line was obtained without exposure to chemotherapeutic agents. Swelling‐activated whole‐cell Cl− current (Icl,swell) was elicited by lowering the bath osmolality. Icl,swell, was characterized in detail in the pgp1‐transfected mouse cell line and compared with that of its parental cell line. Expression of Pgp did not modify the magnitude or properties of Icl,swell, except that addition of the anti‐Pgp antibody C219 to the pipette solution inhibited this current by 75% only in the Pgp‐expressing cells. I Cl,swell in the mouse Pgp‐expressing cell line was compared with that in a Pgp‐expressing hamster fibroblast cell line. The characteristics of ICl,swell (voltage dependence, blocker sensitivity, anion selectivity sequence, requirement for hydrolysable ATP) in Pgp‐expressing cells were different between the two cell lines. These results suggest that the channel(s) responsible for ICl,swell are different between the two cell lines. In addition, C219 inhibited ICl,swell in both Pgp‐expressing cell lines, even though they seem to express different swelling‐activated Cl− channels. We conclude that firstly, Pgp is not a swelling‐activated Cl− channel; secondly, it possibly functions as a Cl− channel regulator; and thirdly, ICl,swell is underlined by different Cl− channels in different cells.

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“…Second, in some but not all cell types, Mdr1 P-glycoproteins regulate swelling-activated Cl Ϫ currents (I Cl-swell ). Effects include enhancement of I Cl-swell and endowment of Cl Ϫ channel sensitivity to protein kinase C (mdr1 gene transfer) and increase in I Cl-swell for a given hypotonic stress (P-glycoprotein overexpression) (7,8). The cellular mechanisms involved in these responses and the implications for other cell types have yet to be clarified.…”

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confidence: 99%

Hepatocellular ATP-binding Cassette Protein Expression Enhances ATP Release and Autocrine Regulation of Cell Volume

Roman¹,

Wang²,

Lidofsky³

et al. 1997

Journal of Biological Chemistry

157

165

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Extracellular ATP is a potent signaling factor that modulates a variety of cellular functions through the activation of P 2 purinergic receptors in the plasma membrane. These receptors are widely distributed among different liver cell types, including hepatocytes, cholangiocytes, macrophages, and endothelial cells, but the physiologic roles have not been fully defined. Cells release ATP in response to both osmotic and mechanical stimuli, and one mechanism may involve opening of a channel-like pathway (1, 2). In respiratory epithelia, ATP release stimulated by cytosolic cAMP activates outwardly rectified Cl Ϫ channels coupled to P 2U receptors and enhances Cl Ϫ secretion (3).Recent studies in a model liver cell line support an alternative pathway where increases in cell volume induce conductive ATP efflux. In these cells, removal of extracellular ATP or P 2 receptor blockade prevents both Cl Ϫ channel activation and volume recovery (1). These findings suggest functional interactions between ATP release, P 2 receptor stimulation, and Cl Ϫ channel opening in epithelial secretion and volume regulation.Members of the ATP-binding cassette (ABC) 1 protein family are likely to be relevant to this volume regulatory pathway for two reasons. First, while the molecular basis for the transmembrane ATP conductance has not been established, heterologous expression or up-regulation of ABC family members in some cell models is associated with enhanced electrodiffusional ATP release. In cystic fibrosis respiratory epithelia, cAMP fails to stimulate channel-mediated ATP efflux, a response that is present in native epithelia; CFTR gene transfer restores the ATP conductance (3, 4). In other cell lines, ATP release is proportional to the expression of mammalian and Drosophila Mdr1 P-glycoproteins (5, 6). Second, in some but not all cell types, Mdr1 P-glycoproteins regulate swelling-activated Cl Ϫ currents (I Cl-swell ). Effects include enhancement of I Cl-swell and endowment of Cl Ϫ channel sensitivity to protein kinase C (mdr1 gene transfer) and increase in I Cl-swell for a given hypotonic stress (P-glycoprotein overexpression) (7,8). The cellular mechanisms involved in these responses and the implications for other cell types have yet to be clarified.In hepatocytes, P-glycoproteins transport both amphipathic compounds and phospholipids across canalicular membranes into bile (9, 10). However, the functions of multiple other ABC members present in liver cells are unknown. In light of the putative association of certain ABC proteins with channelmediated ATP and Cl Ϫ transport, we sought to investigate the role of hepatocellular ABC proteins in these processes. Findings in rat HTC hepatoma cells were compared with those in a selected population of HTC cells (HTC-R) that overexpress both endogenous and novel Mdr proteins (11). These studies demonstrate that inhibition of P-glycoprotein transport prevents recovery from swelling and that overexpression of Mdr proteins is associated with enhanced ATP release, volume recovery, and cell surv...

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Selection for MDR1/P-glycoprotein enhances swelling-activated K+ and Cl- currents in NIH/3T3 cells

Cited by 70 publications

References 16 publications

Volume-sensitive Chloride Channel Activity Does Not Depend on Endogenous P-glycoprotein

Volume-sensitive Chloride Channel Activity Does Not Depend on Endogenous P-glycoprotein

P‐glycoprotein is not a swelling‐activated Cl⁻ channel; possible role as a Cl⁻ channel regulator

Hepatocellular ATP-binding Cassette Protein Expression Enhances ATP Release and Autocrine Regulation of Cell Volume

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Selection for MDR1/P-glycoprotein enhances swelling-activated K+ and Cl- currents in NIH/3T3 cells

Cited by 70 publications

References 16 publications

Volume-sensitive Chloride Channel Activity Does Not Depend on Endogenous P-glycoprotein

Volume-sensitive Chloride Channel Activity Does Not Depend on Endogenous P-glycoprotein

P‐glycoprotein is not a swelling‐activated Cl− channel; possible role as a Cl− channel regulator

Hepatocellular ATP-binding Cassette Protein Expression Enhances ATP Release and Autocrine Regulation of Cell Volume

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P‐glycoprotein is not a swelling‐activated Cl⁻ channel; possible role as a Cl⁻ channel regulator