The marked slowing of deactivation is one of the most prominent effects of CNIH-2 on heterologously expressed AMPARs. Does CNIH-2 make any contribution to the kinetics of AMPARs in CA1 pyramidal neurons? As discussed above, the speeding of AMPAR kinetics in neurons lacking CNIH-2/-3 can be fully accounted for by the selective loss of GluA1-containing Fulvestrant receptors without any need for a direct action of CNIH-2 on the gating of surface/synaptic AMPARs, raising the question as to whether CNIH-2 is, in fact, associated with surface/synaptic AMPARs. Results from other groups (Gill et al., 2011; Kato et al., 2010a),

based largely on data from heterologous cells, found that CNIH proteins prevent AMPAR resensitization, suggesting that the lack of resensitization in neurons is due to the presence of CNIH proteins. However, we failed to see resensitization in neurons lacking CNIH proteins

(Figure S3C). We also found that γ-8 reverses the effects of CNIH-2 on the deactivation of GluA1A2 heteromers. Taken together, these findings may leave very little room for a physiologically relevant role for CNIH proteins on synaptic AMPAR gating in neurons and perhaps diminish the relevance of arguments concerning the presence of CNIH proteins on surface AMPARs. However, we do detect the expression of endogenous CNIH on the surface of neurons and are able to observe effects of CNIH-2 on synaptic AMPAR gating in the absence of γ-8. Therefore, Quisinostat price it is possible for CNIH proteins to associate with synaptic AMPARs. As stated above, such data point to a selective and potentially inert association of CNIH proteins with GluA1 subunits of synaptic GluA1A2 heteromers, with γ-8 bound to all four subunits, Resminostat as previously proposed (Shi et al., 2009). How do CNIH-2/-3 control the level of AMPARs on the surface of hippocampal pyramidal neurons? One possibility is that in the absence of CNIH-2/-3, AMPAR protein is lost, similar to

what is seen in γ-8 KO mice (Rouach et al., 2005). However, the modest loss of AMPAR protein seen in the NexCnih2−/− mice cannot explain the profound loss of surface AMPARs. Rather, our data suggest that the maturation of AMPARs is impaired and that the immature receptors are retained in the ER/cis-Golgi. As pointed out previously ( Shi et al., 2009), such a role is remarkably similar to the established role of the yeast (Erv14p) and Drosophila (Cni) CNIH homologs, in which these proteins serve as chaperones that aid in the forward trafficking of EGFR ligands from the ER to Golgi ( Bökel et al., 2006; Castillon et al., 2009; Roth et al., 1995). However, unlike the yeast and Drosophila homologs, but analogous to its effects in HEK cells, CNIH-2 can remain associated with neuronal AMPARs, at least in the absence of γ-8 protein. More specifically, our results indicate that CNIH is essential for the functional expression of GluA1-containing receptors on the surface.