Control of volume-sensitive chloride channel inactivation by the coupled action of intracellular chloride and extracellular protons Article uri icon

abstract

  • The volume-sensitive chloride current (IClVol) exhibit a time-dependent decay presumably due to channel inactivation. In this work, we studied the effects of chloride ions (Cl-) and H%2b ions on IClVol 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 pHi=pH e=7.3), IClVol in HEK cells shows a large decay at positive voltages but in HL-60 cells IClVol remained constant independently of time. In HEK-293 cells, simultaneously raising the [Cl -]e and [Cl-]i from 25 to 140 mM (with pHe=pHi=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 pHe 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 IClVol decay was seen when the pHe was reduced from 7.3 to 5.5. Our data show that inactivation of IClVol can be controlled by changing either the Cl- or H%2b 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 %2b 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%2b and Cl- ions to the channel followed by a voltage-dependent conformational change that ultimately causes inactivation. © 2010 Springer-Verlag.

publication date

  • 2010-01-01