Grid2ip is a postsynaptic scaffolding protein that contains one formin homology 2 (FH2) domain and two PDZ (postsynaptic density-95/discs-large/ZO-1) domains. Expressed in Purkinje cells of the cerebellum and localizing specifically to parallel fiber synapses, Grid2ip interacts with the C-terminus of GluR-Delta 2 and, via this interaction, links GluR-Delta 2 with various signaling molecules and the Actin cytoskeleton. GluR-Delta 2 is a glutamate receptor with an important role in motor learning, cerebellar wiring and synaptic plasticity. Due to alternative splicing events, three Grid2ip isoforms exist, namely L-delphilin, S-delphilin (or delphilin-Alpha) and delphilin-Beta. Each isoform exhibits individual expression patterns and protein interactions. Isoform 2, delphilin-Alpha, is palmytoylated, a modification that is essential for the enhanced expression of GluR-Delta 2 on the cell surface. This modification of delphilin-Alpha also mediates the accumulation of delphilin-Alpha in dendritic spines.