GluA2-lacking, calcium-permeable AMPA receptors--inducers of plasticity?

AMPA receptors (AMPARs) are heterotetromeric complexes composed of GluA1-4 subunits. They are glutamate-gated channels traditionally considered solely as ion carriers for postsynaptic depolarization. However, the existence and dynamic regulation of GluA2-lacking, calcium-permeable AMPARs (Cp-AMPARs) enable these special receptors to serve also as signaling molecules presumably via calcium influx. Recent studies have implicated Cp-AMPARs in several types of synaptic plasticity, including homeostatic synaptic regulation and Hebbian synaptic plasticity. Cp-AMPARs are usually expressed transiently at an early stage of synaptic plasticity, but are then replaced with normal GluA2-containing receptors, indicating a role for Cp-AMPARs in induction, rather than the maintenance, of synaptic plasticity.