Overview
- Peptide NVGNINNDKKDETYR(C), corresponding to amino acid residues 179-193 of rat GluR2 (Accession P19491). Extracellular, N-terminus.
- Perfusion fixed, frozen floating rat and mouse brain sections (1:20).
Expression of AMPA Receptor 2 (GluR2) in mouse brainImmunohistochemical staining of frozen free-floating of the molecular layer of the mouse cerebellum using Anti-GluR2 (GluA2) (extracellular)-ATTO Fluor-488 Antibody (#AGC-005-AG), (1:20). Both dendrites of Purkinje cells (arrows) were stained (green). DAPI counterstain (blue) helps define the layers: granule (G), Purkinje (P), and molecular (M).
AMPA receptors are members of the glutamate receptor family of ion channels that also include the NMDA and kainate receptors. The three subfamilies are named after the original synthetic agonists that were identified as selective ligands of each subfamily.
The α-amino-3-hydroxy-5-methyl-4-isoazolepropionic acid (AMPA) receptor subfamily includes four members, AMPA1-AMPA4, that are also known as GluR1-GluR4, respectively.
The functional AMPA channel is believed to be a tetramer. Most neuronal AMPA receptors are heterotetramers composed of AMPA1 plus AMPA2 or AMPA2 plus AMPA3, although homotetramers are also found.
AMPA receptors are permeable to Na+, K+, and Ca2+ cations. Permeability to Ca2+ is dependent upon the presence of AMPA2: whenever this subunit is present, the channel is impermeable to Ca2+. Ca2+ permeability of the AMPA2 receptor subunit is determined by the presence of arginine (R), as a result of RNA editing, at a critical site in the pore loop that is occupied by glutamine (Q) in the other AMPA subunits. Since most AMPA2 subunits in the adult brain have undergone RNA editing and most AMPA receptors contain the AMPA2 subunit, most native AMPA receptors are impermeable to Ca2+.
Gating of AMPA receptors by glutamate is extremely fast and therefore the AMPA receptors mediate most excitatory (depolarizing) currents in the brain during basal neuronal activity. The depolarization caused by the activation of post-synaptic AMPA receptors is necessary for the activation of NMDA receptors that open only in the presence of both glutamate and a depolarized membrane.
Synaptic strength, defined as the level of post-synaptic depolarization, can be long term (hence the term long term potentiation, LTP) and therefore induces changes in signaling and protein synthesis in the activated neuron. These changes are associated with memory formation and learning.
Changes in synaptic strength are thought to involve rapid movement of the AMPA receptors in and out of the synapses and a great deal of effort has been focused on understanding the mechanisms that govern AMPA receptor trafficking.
