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. Interacts with the C-terminal tail of PRLHR (By similarity). Interacts with EFNB1, EFNB3, GRIA2, GRIA3, CSGP4 and GRIPAP1. Can form homomultimers and heteromultimers with GRIP1. Isoform 1 was found in synaptic plasma membrane and postsynaptic density. Isoform 2 was found at excitatory synapses and also at non-synaptic membranes and within intracellular compartments. Isoform 3 was found in synaptic plasma membrane and postsynaptic density. Isoform 3 was also found in dendrites where it was associated with microtubules, endoplasmic reticulum and dendritic spines. Isoform 4 was exclusively membrane associated. Brain specific. Isoform 1 is expressed in the olfactory bulb, cortex and hippocampus and was also expressed at lower levels in thalamus, cerebellum and spinal cord. Isoform 3 is expressed in pyramidal cells of cortex and hippocampus, striatum, thalamus, hypothalamus, stellate cells of cerebellum, and brainstem. Isoform 2 and isoform 4 are expressed in cortex, hippocampus, thalamus, cerebellum, brainstem and spinal cord. In hippocampal neurons isoform 4 is found abundantly in spine structures. Isoform 2 is abundant in the cell body and also found in dendritic shafts. Isoform 1 expression was relatively low early in development and increased postnatally, reaching a peak at P14. Isoform 3 is detected at low levels prior to P9, whereupon its expression increases, with the highest levels in the adult. PDZ 5 mediates the C-terminal binding of GRIA2 and GRIA3. PDZ 6 mediates interaction with the PDZ recognition motif of EFNB1. PDZ 7 mediates interaction with CSPG4. Palmitoylation of isoform 4 mediates membrane location. Belongs to the GRIP2 family.