Fig. 4.
KIR2.1 is inhibited by intracellular acidification. (A) The current in a HEK cell heterologously expressing KIR2.1 is inhibited by 20 mM acetic acid at pH 6, but not by pH 6 alone. Note that the pH 6 solution evokes an inward current carried by acid-sensing ion channels (ASIC). (B) Average data from seven cells as in A normalized against the current magnitude before the application of acid. ****P < 0.0001 using paired two-tailed Student’s t test. (C) The I–V relationship of the KIR2.1 current at times indicated in A. (D) Excised patch recording from a KIR2.1 transfected HEK cell in response to acids. The bath solution contained 150 mM KCl, 1 mM EGTA, and 1 mM EDTA. The membrane was held at −80 mV. The application of pH 5.5 completely inhibited channel activity, and channel activity was partially restored by return to neutral pH. Similar results were observed in five cells.