Control of volume-sensitive chloride channel inactivation by the coupled action of intracellular chloride and extracellular protons.
The volume-sensitive chloride current (I(ClVol)) exhibit a time-dependent decay presumably due to channel inactivation. In this work, we studied the effects of chloride ions (Cl(-)) and H(+) ions on I(ClVol) decay recorded in HEK-293 and HL-60 cells using the whole-cell patch clamp technique. Under control conditions ([Cl(-)](e) = [Cl(-)](i) = 140 mM and pH(i) = pH(e) = 7.3), I(ClVol) in HEK cells shows a large decay at positive voltages but in HL-60 cells I(ClVol) remained constant independently of time. In HEK-293 cells, simultaneously raising the [Cl(-)](e) and [Cl(-)](i) from 25 to 140 mM (with pH(e) = pH(i) = 7.3) increased the fraction of inactivated channels (FIC). This effect was reproduced by elevating [Cl(-)](i) while keeping the [Cl(-)](e) constant. Furthermore, a decrease in pH(e) from 7.3 to 5.5 accelerated current decay and increased FIC when [Cl(-)] was 140 mM but not 25 mM. In HL-60 cells, a slight I(ClVol) decay was seen when the pH(e) was reduced from 7.3 to 5.5. Our data show that inactivation of I(ClVol) can be controlled by changing either the Cl(-) or H(+) concentration or both. Based on our results and previously published data, we have built a model that explains VRAC inactivation. In the model the H(+) binding site is located outside the electrical field near the extracellular entry whilst the Cl(-) binding site is intracellular. The model depicts inactivation as a pore constriction that happens by simultaneous binding of H(+) and Cl(-) ions to the channel followed by a voltage-dependent conformational change that ultimately causes inactivation.
Hernández-Carballo
Carmen Y
CY
Instituto de Física, Universidad Autónoma de San Luis Potosí, Ave. Dr. Manuel Nava #6, San Luis Potosí, San Luis Potosí, SLP 78290, México.
De Santiago-Castillo
José A
JA
Rosales-Saavedra
Teresa
T
Pérez-Cornejo
Patricia
P
Arreola
Jorge
J
D002712:Chlorides / Q000378:metabolism*; D018922:HL-60 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000378:metabolism; D007700:Kinetics; D018408:Patch-Clamp Techniques; D011522:Protons; D050994:Voltage-Dependent Anion Channels / Q000378:metabolism*
D002712:Chlorides; D011522:Protons; D050994:Voltage-Dependent Anion Channels
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