Extended Data Fig. 10: Calcium block data of A1_A2, A1_A2γ2, and A1_A2γ2 + CIHN3 captured by permeation model (Model 4.2) with identical voltage dependences.
From: GluA2-containing AMPA receptors form a continuum of Ca2+-permeable channels
a. Black dots indicate normalized AMPAR conductance at various calcium concentrations for four different AMPAR complexes (top to bottom) and various voltages (left to right). The red lines show the fit of Model 4.2. Shading indicates 95% confidence interval of model fit (bootstrap, n = 100). b. Optimal parameter values for the voltage dependence of site B1 (\({\delta }_{1}\)) and site B2 (\({\delta }_{3}\)) after repeatedly fitting Model 4.2 to 100 bootstrap samples of the data. The voltage dependence of B2 was allowed to differ for GluA1+GluA2R607Eγ2. Notice the second peak in density for the voltage dependence of binding site B2, indicating that in the mutant receptor, binding site B2 sits more shallowly in the membrane electric field compared to the other AMPARs studied. c. Dissociation constants of each of the four transitions in Model 4.2 after fitting to each of the four AMPAR complexes. Vertical lines reflect 95% confidence interval (bootstrap, n = 100). d. Dissociation constants of calcium binding, same as panel c, now plotted against the calcium permeability of each AMPAR. The dissociation constants are positively associated with calcium permeability for CaO↔B1 (ρ = 0.95, spearman correlation, p < 10-9), CaO↔B2 (ρ = 0.96, p < 10-9), but not for Cai↔B2 (ρ = 0.08, p = 0.09).
