These findings could be explained by CNIH-2 and γ-8 binding to the same site on GluA1 subunits with CNIH-2 displacing γ-8, or the two proteins binding to separate sites. The fact that the slowing of kinetics seen with CNIH-2 is the same in GluA1-containing AMPARs with covalently attached γ-8 (Shi et al., 2010), suggests that CNIH-2 is not displacing γ-8. Furthermore, the fact that the IKA/IGlu ratio, a sensitive measure of γ-8/AMPAR stoichiometry, is unchanged (Figure 6Aii) also strongly argues that CNIH-2 is not displacing γ-8 and that γ-8 and CNIH-2 are able to co-occupy GluA1 subunits. These results, however, do not explain why CNIH-2 appears to occupy all available binding sites on neuronal AMPARs and yet native neuronal AMPAR kinetics are substantially faster than what is observed when CNIH-2 and γ-8 are expressed with homomeric GluA1. Might GluA2 behave differently from GluA1, in that essentially all native AMPARs in CA1 pyramidal neurons contain the GluA2 subunit (Lu et al., 2009)? We therefore examined the effect of CNIH-2 on GluA2 homomers in HEK cells. Unedited GluA2(Q) was used owing to
