May regulate trafficking and current kinetics of AMPA-type glutamate receptor (AMPAR) at synapses. Interacts with AMPAR subunits GRIA1 and GRIA2. Brain-specific. Highly expressed in cerebellum and olfactory bulb. Undetectable in the brain of 17 dpc embryos. Expressed in olfactory bulb from postnatal day 1 (P1) and then in cerebellum from postnatal day 14 (P14). Belongs to the shisa family.