Fig. 1.

Binding and functional characterization of mutations on PKA putative sites in the α4 subunit. Voltage-clamp recordings were used to determine the macroscopic response ofmutations α4S364Aβ2, α4S364Dβ2, α4S471Aβ2, α4S471Dβ2, α4S490Aβ2, α4S490Dβ2 andwild-type α4β2 nAChRs expressed in Xenopus laevis oocytes to several ACh and nicotineconcentrations. (A) Family of ACh-induced macroscopic currents. Calibration bars are shown for all family of currents, horizontal bars indicate time (5 s) and vertical bars indicate the inward current (500 nA). (B) Dose-response relationships obtained by voltage-clamp using ACh as an agonist. ACh dose-response curves were determined using seven ACh concentrations (0.1, 1, 3, 10, 30, 100, and a seventh concentration ranging from 300 to 1000 μM depending on the mutant). The responses were normalized to the maximum response (I/Imax). (C) Left panel, comparison of the macroscopic peak currents of all the mutations and wild-type receptor shown in nA. Right panel, results of the ¹²⁵I-labeled epibatidine binding experiments performed in Xenopus laevis oocytes expressing the mutations α4S364Aβ2, α4S364Dβ2, α4S471Aβ2, α4S471Dβ2, α4S490Aβ2, α4S490Dβ2 and wild-type α4β2 nAChRs shown in fmoles (n=6-17) (*** p<0.0005, ** p<0.005).