Required to maintain a pool of extrasynaptic AMPA-regulated glutamate receptors (AMPAR) which is necessary for synapse development and function (PubMed:29490264). Regulates AMPAR function and synaptic transmission during development but is dispensable at mature hippocampal synapses (PubMed:29490264, PubMed:31216424). Plays a role in regulating basal phosphorylation levels of glutamate receptor GRIA1 and promotes GRIA1 and GRIA2 cell surface expression (PubMed:31216424). Component of the outer core of AMPAR complex. AMPAR complex consists of an inner core made of 4 pore-forming GluA/GRIA proteins (GRIA1, GRIA2, GRIA3 and GRIA4) and 4 major auxiliary subunits arranged in a twofold symmetry. One of the two pairs of distinct binding sites is occupied either by CNIH2, CNIH3 or CACNG2, CACNG3. The other harbors CACNG2, CACNG3, CACNG4, CACNG8 or GSG1L. This inner core of AMPAR complex is complemented by outer core constituents binding directly to the GluA/GRIA proteins at sites distinct from the interaction sites of the inner core constituents. Outer core constituents include at least PRRT1, PRRT2, CKAMP44/SHISA9, FRRS1L and NRN1. The proteins of the inner and outer core serve as a platform for other, more peripherally associated AMPAR constituents. Alone or in combination, these auxiliary subunits control the gating and pharmacology of the AMPAR complex and profoundly impact their biogenesis and protein processing. Expressed in the brain (at protein level) (PubMed:22632720). In brain, expressed throughout the hippocampus with weak expression in the olfactory bulb and neocortex (at protein level) (PubMed:29490264). Decreased Gria1/GluA1 and Gria2/GluA2 density at extrasynaptic sites and increased density of Gria1 at synapses (PubMed:29490264). Reduced cell surface expression of Gria1 and Gria2 (PubMed:31216424). Reduced phosphorylation of Gria1 'Ser-863' and increased phosphorylation of Gria1 'Ser-849' (PubMed:31216424). Reduced synaptic transmission in immature hippocampal neurons (PubMed:29490264). No change in basal synaptic transmission in mature hippocampal neurons (PubMed:31216424). Shown to impair tetanus-induced long-term potentiation (LTP) in 8-12 week old mice in one study (PubMed:29490264). Another study shows no effect on LTP in young mature mice at postnatal days 24-36 (PubMed:31216424). Severely impaired long-term depression (PubMed:31216424). Deficiency in cognitive learning and memory tasks (PubMed:29490264). Belongs to the CD225/Dispanin family.