Volume-Dependent Atp-Conductive Large-Conductance Anion Channel as a Pathway for Swelling-Induced Atp Release

Volume-Dependent Atp-Conductive Large-Conductance Anion Channel as a Pathway for Swelling-Induced... In mouse mammary C127i cells, during whole-cell clamp, osmotic cell swelling activated an anion channel current, when the phloretin-sensitive, volume-activated outwardly rectifying Cl − channel was eliminated. This current exhibited time-dependent inactivation at positive and negative voltages greater than around ±25 mV. The whole-cell current was selective for anions and sensitive to Gd 3 +. In on-cell patches, single-channel events appeared with a lag period of ∼15 min after a hypotonic challenge. Under isotonic conditions, cell-attached patches were silent, but patch excision led to activation of currents that consisted of multiple large-conductance unitary steps. The current displayed voltage- and time-dependent inactivation similar to that of whole-cell current. Voltage-dependent activation profile was bell-shaped with the maximum open probability at −20 to 0 mV. The channel in inside-out patches had the unitary conductance of ∼400 pS, a linear current-voltage relationship, and anion selectivity. The outward (but not inward) single-channel conductance was suppressed by extracellular ATP with an IC 50 of 12.3 mM and an electric distance (δ) of 0.47, whereas the inward (but not outward) conductance was inhibited by intracellular ATP with an IC 50 of 12.9 mM and δ of 0.40. Despite the open channel block by ATP, the channel was ATP-conductive with P ATP /P Cl of 0.09. The single-channel activity was sensitive to Gd 3 +, SITS, and NPPB, but insensitive to phloretin, niflumic acid, and glibenclamide. The same pharmacological pattern was found in swelling-induced ATP release. Thus, it is concluded that the volume- and voltage-dependent ATP-conductive large-conductance anion channel serves as a conductive pathway for the swelling-induced ATP release in C127i cells. ATP-conducting channel maxi chloride channel osmotic cell swelling volume regulation Footnotes Abbreviations used in this paper: VDAC, voltage-dependent anion channel; VDACL, voltage-dependent ATP-conductive large-conductance; VSOR, volume-sensitive outwardly rectifying. Submitted: 2 March 2001 Revision requested 16 July 2001 Accepted: 18 July 2001 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of General Physiology Rockefeller University Press

Volume-Dependent Atp-Conductive Large-Conductance Anion Channel as a Pathway for Swelling-Induced Atp Release

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Publisher
Rockefeller University Press
Copyright
© 2001 The Rockefeller University Press
ISSN
0022-1295
eISSN
1540-7748
DOI
10.1085/jgp.118.3.251
Publisher site
See Article on Publisher Site

Abstract

In mouse mammary C127i cells, during whole-cell clamp, osmotic cell swelling activated an anion channel current, when the phloretin-sensitive, volume-activated outwardly rectifying Cl − channel was eliminated. This current exhibited time-dependent inactivation at positive and negative voltages greater than around ±25 mV. The whole-cell current was selective for anions and sensitive to Gd 3 +. In on-cell patches, single-channel events appeared with a lag period of ∼15 min after a hypotonic challenge. Under isotonic conditions, cell-attached patches were silent, but patch excision led to activation of currents that consisted of multiple large-conductance unitary steps. The current displayed voltage- and time-dependent inactivation similar to that of whole-cell current. Voltage-dependent activation profile was bell-shaped with the maximum open probability at −20 to 0 mV. The channel in inside-out patches had the unitary conductance of ∼400 pS, a linear current-voltage relationship, and anion selectivity. The outward (but not inward) single-channel conductance was suppressed by extracellular ATP with an IC 50 of 12.3 mM and an electric distance (δ) of 0.47, whereas the inward (but not outward) conductance was inhibited by intracellular ATP with an IC 50 of 12.9 mM and δ of 0.40. Despite the open channel block by ATP, the channel was ATP-conductive with P ATP /P Cl of 0.09. The single-channel activity was sensitive to Gd 3 +, SITS, and NPPB, but insensitive to phloretin, niflumic acid, and glibenclamide. The same pharmacological pattern was found in swelling-induced ATP release. Thus, it is concluded that the volume- and voltage-dependent ATP-conductive large-conductance anion channel serves as a conductive pathway for the swelling-induced ATP release in C127i cells. ATP-conducting channel maxi chloride channel osmotic cell swelling volume regulation Footnotes Abbreviations used in this paper: VDAC, voltage-dependent anion channel; VDACL, voltage-dependent ATP-conductive large-conductance; VSOR, volume-sensitive outwardly rectifying. Submitted: 2 March 2001 Revision requested 16 July 2001 Accepted: 18 July 2001

Journal

The Journal of General PhysiologyRockefeller University Press

Published: Sep 1, 2001

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