Involved in negative regulation of anterograde synaptic vesicle transport; negative regulation of receptor localization to synapse; and regulation of neurotransmitter receptor activity. Acts upstream of or within glutamatergic synaptic transmission; localization within membrane; and regulation of membrane potential. Located in dendritic shaft and postsynaptic membrane. Part of AMPA glutamate receptor complex. Is active in glutamatergic synapse. Is integral component of postsynaptic density membrane. Orthologous to human CNIH2 (cornichon family AMPA receptor auxiliary protein 2). [provided by Alliance of Genome Resources, Apr 2022]