Extended Data Fig. 6: Structural and functional comparison of GluA3-R and GluA3-G.

a, Summary graph (mean ± SD) for flow cytometry data of the surface expression of GluA3-R, -G, GluA2, and GluA3-R/TARPγ2. Geometric mean fluorescence of each sample was normalized to the average value for GluA3-R on that day (indicated by green dashed line). Welch’s ANOVA followed by Dunnet’s multiple comparison test, (W_{3, 8.598} = 245.9); ****p  <  0.0001. b, Representative motion-corrected micrographs of the apo-state GluA3-G/γ2 (left) and GluA3-R/γ2 (right) (scale bar, 50 nm). The R-form receptor is prone to aggregation on the cryoEM grids. The blue circles highlight the aggregates on the GluA3-R grids. c, Selected 3D classes of GluA3-G/γ2 (left) and GluA3-R/γ2 (right) in the apo state, with the LBD fitted in. The R-form exhibits the splitting of the LBD dimer. d, Representative 3D classes of the apo state of GluA3-G/γ2, showcasing that the dimer-of-dimer conformation of the LBD layer is preserved at all times. e, Representative 3D classes of the apo state of GluA3-R/γ2, showcasing that the LBD dimers inhabit a continuous spectrum of states ranging from intact LBD dimers (black box) to monomeric, split LBD dimers (orange box). The double-sided arrows point towards the split LBDs in the individual classes. f, The surface representation of the models fitted into the selected classes of GluA3-G/γ2 (c) and GluA3-R/γ2 (d). The red dotted lines denote the distance between R439 (left) and G439 (right) of the B/D subunit, which are 21.3 Å and 48.7 Å, respectively. g, The resolved apo state NTD dimer of the GluA3-R form (side and front view, left and right respectively) remains flat and docked on the LBD in a similar way. h, Summary bar graphs (mean ± SD) showing the rectification index (RI), defined as the ratio of peak currents recorded at +40 mV to those at –60 mV, determined for two transfection conditions: 4:1 and 1:4 ratios of GluA3-G/-R/A1 to GluA2(R). i, Averaged current–voltage (I–V) relationships of AMPARs co-expressed at the indicated transfection ratios, with all currents normalized to the amplitude at –100 mV. Error bars denote SEM.