Regulates the trafficking to the somatodendritic compartment and gating properties of AMPA-selective glutamate receptors (AMPARs) (PubMed:18341993). 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 (By similarity). 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 (PubMed:18341993). Displays a somatodendritic localization and is excluded from axons in neurons. Belongs to the PMP-22/EMP/MP20 family. CACNG subfamily.