May play a role as a localized scaffold for the assembly of a multiprotein signaling complex and as mediator of the trafficking of its binding partners at specific subcellular location in neurons (PubMed:10197531). Through complex formation with NSG1, GRIA2 and STX12 controls the intracellular fate of AMPAR and the endosomal sorting of the GRIA2 subunit toward recycling and membrane targeting (By similarity). {ECO:0000250|UniProtKB:P97879, ECO:0000269|PubMed:10197531}. This is the function of Ensembl gene identifier ENSG00000155974 (GRIP1, glutamate receptor interacting protein 1).