Fig. 2
From: Identification of a unique Ca2+-binding site in rat acid-sensing ion channel 3
A glutamate for glycine mutation in cASIC1 shifts pH sensitivity to more alkaline values. Whole-cell patch-clamp electrophysiology recordings of cASIC1, rASIC3, and cASIC1 Gly429Glu in transfected CHO-K1 cells (Vhold = −70 mV) are shown and summarized. Each expressed receptor was exposed to an acidic test solution in the presence or absence of CaCl2 for 5 s before returning to pH 8.0 external solution in the presence or absence of CaCl2. The summarized data show the response to low pH in the presence of Ca2+ (filled symbols) and in the absence of Ca2+ (open symbols). a cASIC1 had a calculated pH50 of 6.90 ± 0.03 with a Hill value of 4.07 ± 0.75 in the presence of Ca2+ (n = 5 cells). In the absence of Ca2+, the pH50 was 7.01 ± 0.03 with a Hill value of 2.05 ± 0.23, with both being significantly different from the control (p < 0.001, n = 5 cells). b rASIC3 had a pH50 of 6.86 ± 0.02 with a Hill value of 3.54 ± 1.08 in the presence of Ca2+ (n = 4 cells) compared to a pH50 of 7.32 ± 0.04 (p < 0.001) and Hill value of 1.48 ± 0.20 (p < 0.05) in the absence of Ca2+ (n = 4 cells). c The cASIC1 G429E mutant had a pH50 of 6.98 ± 0.02 (p < 0.05 compared to wild-type cASIC1) and Hill value of 3.96 ± 0.33 in the presence of Ca2+ (n = 9) and pH50 of 7.42 ± 0.01 and Hill value of 4.99 ± 0.08 in the absence of Ca2+ (n = 6 cells). Here, the pH50 value was significantly different from the calcium response of the mutant (p < 0.001) and to the wild-type cASIC1 response under the same conditions (p < 0.01). Error bars are s.e.m.
