Fig. 4.
Effects of VX-770 on mCFTR. A: representative macropatch currents of mCFTR recorded under high-PKA conditions (1 mM MgATP + 638 U/ml PKA) in the absence and presence of 0.5 μM VX-770. mCFTR channels were activated by 20 min in high-PKA conditions followed by addition of 0.5 μM VX-770 for 5 min. B: mCFTR was activated under standard conditions (1 mM MgATP + 127.6 U/ml PKA) for 20 min, then exposed to 0.5 μM VX-770 along with ATP + PKA for 5 min. C: mCFTR currents were potentiated by VX-770 to a similar degree under high- and low-PKA conditions, suggesting that the effect was not sensitive to channel activity level. D: the concentration dependence of the increase in mCFTR current induced by VX-770 is shown; n = 4–6 patches at each concentration. The solid line indicates the fit with a 1-site, ligand-saturation-binding equation giving an apparent Kd = 7.32 nM at VM = −100 mV. E: representative single-channel current traces of mCFTR from 1 patch recorded under the same conditions as Fig. 1. −VX-770, 1 mM MgATP + 127.6 U/ml PKA; +VX-770, 200 nM VX-770 + 1 mM MgATP + 127.6 U/ml PKA. F: apparent open probability (NPo) of mCFTR channels in the absence (−VX-770) and presence (+VX-770) of 200 nM VX-770. **P < 0.01 compared with control conditions (−VX-770).