Regulates the trafficking to the somatodendritic compartment and gating properties of AMPA-selective glutamate receptors (AMPARs). Promotes their targeting to the cell membrane and synapses and modulates their gating properties by slowing their rates of activation, deactivation and desensitization. Does not show subunit-specific AMPA receptor regulation and regulates all AMPAR subunits. Thought to stabilize the calcium channel in an inactivated (closed) state. The L-type calcium channel is composed of five subunits: alpha-1, alpha-2/delta, beta and gamma. Acts as an auxiliary subunit for AMPA-selective glutamate receptors (AMPARs). Found in a complex with GRIA1, GRIA2, GRIA3, GRIA4, CNIH2, CNIH3, CACNG2, CACNG4, CACNG5, CACNG7 and CACNG8 (By similarity). Interacts with AP4M1 and GRIA1; associates GRIA1 with the adaptor protein complex 4 (AP-4) to target GRIA1 to the somatodendritic compartment of neurons (By similarity). Displays a somatodendritic localization and is excluded from axons in neurons. Belongs to the PMP-22/EMP/MP20 family. CACNG subfamily.