May play a role in retinal photoreceptors development. Interacts with MPDZ. May interact with GRIA2 (By similarity). Forms a complex with CRB1 and PALS1. Interacts with FASLG. Detected at the outer limiting membrane (OLM) and in the outer plexiform layer (OPL) of the retina. At the OLM, detected apical to the adherens junction (AJ). Expressed in the retina (at protein level). Highly expressed in the retina. Lower amounts are detected in brain, testis, ARPE-19, RPE/choroid and fetal eye. Isoform 5 is retina-specific. Belongs to the MAGUK family.