Figure 6: GluK2a C-terminal sequence is necessary for stabilization of synaptic KARs.

(a) Schematic representation of the GluK2a subunit, illustrating the sites at which the CTD was truncated. (b,c) Sample traces illustrating synaptic currents evoked by mf stimulation in organotypic slices prepared from GluK2^+/+ and GluK2^−/− mice, not transfected (NT) or transfected with 3 ng μl⁻¹ of wt or mutated GluK2a cDNA (Δ4, Δ14, Δ29 and Δ39). Experiments were performed in the presence of bicuculline (10 μM), D-AP5 (50 μM) and NBQX (150 nM). Traces represent the average of synaptic currents evoked at 3 Hz in the absence and in the presence of 25 μM LY303070, to isolate the AMPAR and the KAR component, respectively. In the insert are shown enlargements, by the same proportion, of isolated KAR-EPSCs. (c) Bar graphs summarizing KAR/AMPAR ratios obtained from the experiments presented in b. GluK2^+/+ NT: n=8 cells; GluK2^−/− NT: n=8; GluK2^−/−+GluK2a: n=9 cells; GluK2Δ4: n=12 cells; GluK2Δ14: n=7 cells; GluK2Δ29: n=12 cells; GluK2Δ39: n=8 cells. 40 mice. (d,e) Sample traces illustrating KAR-currents evoked by glutamate uncaging on TEs of CA3 PCs in organotypic slice cultures prepared from GluK2^+/+ and GluK2^−/− mice, not transfected (NT) or transfected with 3 ng μl⁻¹ of wt or mutated GluK2a cDNA (Δ14 and Δ29). (e) Bar graphs summarizing KAR/AMPAR ratios obtained from the experiments presented in d. GluK2^+/+ NT: n=11 cells; GluK2^−/− NT: n=11; GluK2^−/−+GluK2a: n=9 cells; GluK2Δ14: n=11 cells; GluK2Δ29: n=15 cells; 24 mice. In all panels, values are presented as mean ±s.e.m. of n experiments. Data were compared using one-way analysis of variance followed by Dunnett’s multiple comparison test (NS, not significant; P>0.05, **P<0.01 and ***P<0.001).