AMPARs form as heterotetramers of the four pore-lining α-subunits GluA1–4, which are differentially expressed in the mammalian brain. Alternative splicing and RNA editing further enhance their diversity with respect to trafficking and biophysical properties [4]–[12]. The GluA subunits co-assemble with transmembrane AMPAR regulatory proteins (TARPs) that modulate both the subcellular distribution and the biophysical properties of native AMPAR complexes [13]–[16]. Stargazin (γ-2), the prototypical TARP, enhances surface expression of AMPARs, their synaptic targeting and recycling by interaction with the postsynaptic scaffolding protein PSD-95 [17]–[19]. Moreover, TARPs increase charge transfer through individual AMPARs as they slow channel deactivation and desensitization and reduce current rectification by polyamines [20], [21].
