2011). Additional AMPAR auxiliary subunits, unrelated to TARPs, have been identified from a variety of screens (Wang et al., 2008; Zheng et al., 2004). Among these proteins are cornichon-2 and -3 (CNIH-2 and CNIH-3) (Schwenk et al., 2009). In expression systems CNIH-2 markedly slows AMPAR deactivation and desensitization and shares a number of other properties with TARPs (Gill et al., 2011; Gill et al., 2012; Harmel et al., 2012; Kato et al., 2010a; Schwenk et al., 2009; Shi et al., 2010). However, in CGNs and hippocampal neurons no significant effect of CNIH-2 overexpression was observed on AMPAR-mediated synaptic currents (Shi et al., 2010). Thus it was proposed that CNIH-2’s function in neurons was more akin to its yeast and Drosophia homologs, which serve as chaperones in the forward trafficking of EGFR ligands from ER to Golgi (Bokel et al., 2006; Castillon et al., 2009). Additional studies on CNIH-2 supported its role in forward trafficking of neuronal AMPARs (Harmel et al., 2012), but concluded that CNIH-2 remained bound to AMPARs on the surface of neurons (Gill et al., 2011; Harmel et al., 2012; Kato et al., 2010a). Furthermore, it was proposed that CNIH-2 displaced γ-8, the primary TARP expressed in the
