![Figure 5. Voltage activation of WT and H538F mutant CLC-2 channels does not occur with intracellular acetate and acidic external pH. (A) Representative whole-cell recordings at −120 mV from a single cell expressing WT CLC-2. The cell was dialyzed with internal solution containing 140 mM acetate, pHi 6.5, and bathed in solution containing 140 mM Cl−. The external pH was 7.3 (black) or 6.5 (bluish green). n = 5 samples. (B) Representative traces showing activation of CLC-2 in cells dialyzed with 75% Cl− and 25% SCN−, pHi 10. Cells were hyperpolarized to −120 mV in recording solution with pHe 7.3 (black); pHe was thereafter increased to 10 (sky blue). n = 4 samples. (C) ICl(t) recorded at −120 mV from an HEK-293 cell expressing mutant H538F channels. The cell was sequentially exposed to external solutions of pH 7.3 (black) and pH 5.5 (reddish purple). [Cl−]i = [Cl−]e = 140 mM. Average time constants of tail current decay at pH 5.5 and 7.3 are 4.6 ± 0.2 ms and 3.7 ± 0.3 ms, respectively (n = 5). (D) Vm-dependent activation curves in H538F mutant channels recorded at pH 7.3 (black) and pH 5.5 (reddish purple). Continuous lines are Boltzmann fits yielding the following V0.5 and z values: −138.2 ± 4.0 mV and −0.75 ± 0.02 (pHe 7.3); −98.0 ± 8.0 mV and −0.75 ± 0.02 (pHe 5.5; n = 5). (E) ICl(t) recorded at −120 mV from a cell expressing mutant H538F channels and sequentially exposed to external solutions of pH 7.3 (black) and pH 5.5 (reddish purple). Cell was dialyzed with 140 mM acetate, pHi 7.3, and bathed in solution containing 140 mM Cl− at pHe 7.3 or 5.5 (n = 6). (F) Activation of H538F channels in cells dialyzed with 140 mM [Glu]i and bathed in 140 mM [Cl]e. pHi = pHe 7.3 (n = 3). Error bars represent mean ± SEM.](https://cdn.rupress.org/rup/content_public/journal/jgp/147/1/10.1085_jgp.201511424/5/jgp_201511424r_fig5.jpeg?Expires=1767665962&Signature=fNZYBIM3cBhJCia5O2BSZB~0dVkVuWlmQYbjqLEzscPHmkO5O8EfcgS6L3TI6Sgwk8N-D1hOPAS0hrVl6vO7p19We8TL5lJW3k5-9dZoih88zf4LN5QzHXJe2G04oDKPwhl6ivGnVkdHijhJ-7WRAO6SnKcaE2YHAeU-zjllwOTz18t1Mmj0KawBI88WJDI4RSAc42sQNDXohIfY~J~gY9WzR0ll39cT2q5VeLDXOqR8j-bvBHlZwU4JESyuq-K78eUQ20xg2iUd8oRuQITq4Il070A~dnxx4RNQiFldiRVfngx-tHy8x5-34-8LggFsYWYuOnaOJSc7fUe4G04rEg__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Voltage activation of WT and H538F mutant CLC-2 channels does not occur with intracellular acetate and acidic external pH. (A) Representative whole-cell recordings at −120 mV from a single cell expressing WT CLC-2. The cell was dialyzed with internal solution containing 140 mM acetate, pHi 6.5, and bathed in solution containing 140 mM Cl−. The external pH was 7.3 (black) or 6.5 (bluish green). n = 5 samples. (B) Representative traces showing activation of CLC-2 in cells dialyzed with 75% Cl− and 25% SCN−, pHi 10. Cells were hyperpolarized to −120 mV in recording solution with pHe 7.3 (black); pHe was thereafter increased to 10 (sky blue). n = 4 samples. (C) ICl(t) recorded at −120 mV from an HEK-293 cell expressing mutant H538F channels. The cell was sequentially exposed to external solutions of pH 7.3 (black) and pH 5.5 (reddish purple). [Cl−]i = [Cl−]e = 140 mM. Average time constants of tail current decay at pH 5.5 and 7.3 are 4.6 ± 0.2 ms and 3.7 ± 0.3 ms, respectively (n = 5). (D) Vm-dependent activation curves in H538F mutant channels recorded at pH 7.3 (black) and pH 5.5 (reddish purple). Continuous lines are Boltzmann fits yielding the following V0.5 and z values: −138.2 ± 4.0 mV and −0.75 ± 0.02 (pHe 7.3); −98.0 ± 8.0 mV and −0.75 ± 0.02 (pHe 5.5; n = 5). (E) ICl(t) recorded at −120 mV from a cell expressing mutant H538F channels and sequentially exposed to external solutions of pH 7.3 (black) and pH 5.5 (reddish purple). Cell was dialyzed with 140 mM acetate, pHi 7.3, and bathed in solution containing 140 mM Cl− at pHe 7.3 or 5.5 (n = 6). (F) Activation of H538F channels in cells dialyzed with 140 mM [Glu]i and bathed in 140 mM [Cl]e. pHi = pHe 7.3 (n = 3). Error bars represent mean ± SEM.
