Our data, thus far, demonstrate that synaptic expression of GluA1A2 AMPARs is eliminated in the absence of CNIH-2/-3. What then accounts for the fast kinetics of the remaining AMPARs observed after deleting CNIH-2/-3? Importantly, deletion of GluA1 results in the same fast kinetics, suggesting that the kinetics are a direct result of the specific molecular composition of the remaining receptors, which are primarily GluA2A3γ-8 complexes (Lu et al., 2009). Therefore, we next used heterologous cells to evaluate if CNIH-2 affects AMPAR kinetics by specifically regulating GluA1A2 trafficking. We co-expressed GluA2, GluA3 and γ-8 in HEK cells and measured the deactivation of this receptor complex (Figures 4C–E). For all experiments, flip-type AMPAR subunits were evaluated (see Supplemental Experimental Procedures). GluA2A3γ-8 complex deactivation is twice as fast as GluA1A2γ-8, with GluA2A3γ-8 deactivation being virtually identical to the deactivation of AMPARs in CRE-expressing Cnih2/3fl/fl neurons (Figure 4D). Furthermore, the difference in deactivation between GluA1A2γ-8 and GluA2A3γ-8 complexes is virtually identical to the magnitude of change in mEPSC decay in both CRE-expressing conditional GluA1 and CNIH-2/-3 (Gria1fl/fl and Cnih2/3fl/fl) KO neurons (Figure 4E). Thus,
