AMPA- (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid), kainite- and NMDA- (N-methyl-D-aspartate) receptors are the three main families of ionotropic glutamate-gated ion channels. AMPA receptors (AMPARs) are comprised of four subunits (GluR 1-4) that assemble as homo- or hetero-tetramers and mediate the majority of fast excitatory transmissions in the CNS. AMPARs are implicated in synapse formation, stabilization and plasticity. Post-transcriptional modifications (alternative splicing and nuclear RNA editing) and post-translational modifications (glycosylation, phoshorylation) result in a very large number of permutations, fine-tuning the kinetic properties of AMPARs (1). GluR 3 knockout mice exhibited normal basal synaptic transmission and long-term depression (LTD) but enhanced long-term potentiation (LTP). In contrast, GluR 2/3 double knockout mice are impaired in basal synaptic transmission (2). Aberrant GluR 3 expression or activity is implicated in a number of diseases, including autoimmune epilepsy, X-linked mental retardation, Rett's syndrome, amyotrophic lateral sclerosis and Alzheimer disease (3).
