Glutamate ionotropic receptor AMPA type subunit 2 (Glutamate receptor 2, or GluR-2) is a protein that in humans is encoded by the GRIA2 (or GLUR2) gene and it is a subunit found in the AMPA receptors. Glutamate receptor 3 is a protein that in humans is encoded by the GRIA3 gene. Glutamate receptors are the predominant excitatory neurotransmitter receptors in the mammalian brain and are activated in a variety of normal neurophysiologic processes. GRIA2 product belongs to a family of glutamate receptors that are sensitive to alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA), called AMPA receptors, and function as ligand-activated cation channels. These channels are assembled from a combination of 4 subunits, encoded by 4 genes (GRIA1-4). The subunit encoded by this gene (GRIA2) is subject to RNA editing which renders the receptor that it becomes part of impermeable to calcium ions (Ca2+). Human and animal studies suggest that the RNA editing is essential for normal brain function, and defective RNA editing of GRIA2 may be relevant to the etiology of amyotrophic lateral sclerosis (ALS). Alternative splicing, resulting in transcript variants encoding different isoforms, has been noted for GRIA2, which includes the generation of flip and flop isoforms that vary in their signal transduction properties. Genome studies have uncovered a tentative link between defective GRIA3 variants and a highly elevated risk of schizophrenia.