Seems to act as a scaffold molecule at synaptic junctions by assembling neurotransmitter receptors and cell adhesion proteins (By similarity). Plays a role in nerve growth factor (NGF)-induced recruitment of RAPGEF2 to late endosomes and neurite outgrowth (By similarity). May play a role in regulating activin-mediated signaling in neuronal cells (PubMed:10681527). Enhances the ability of PTEN to suppress AKT1 activation (By similarity). Plays a role in receptor-mediated clathrin-dependent endocytosis which is required for ciliogenesis (PubMed:24608321). Interacts (via its WW domains) with DRPLA (By similarity). Interacts (via its second PDZ domain) with PTEN (via unphosphorylated C-terminus); this interaction diminishes the degradation rate of PTEN (By similarity). Interacts (via guanylate kinase domain) with DLGAP1 (By similarity). Interacts (via the PDZ domains) with GRIN2A, GRID2 and NLGN1 (By similarity). Interacts with CTNND2, CTNNB1 and MAGUIN-1 (By similarity). Interacts with ACVR2A, SMAD2 and SMAD3 (PubMed:10681527). Part of a complex consisting of AIP1, ACVR2A, ACVR1B and SMAD3 (PubMed:10681527). May interact with HTR2A (PubMed:14988405). Interacts with RAPGEF2 (By similarity). Identified in a complex with ACTN4, CASK, IQGAP1, NPHS1, SPTAN1 and SPTBN1 (By similarity). Interacts with DDN (By similarity). Found in a complex, at least composed of KIDINS220, MAGI2, NTRK1 and RAPGEF2; the complex is mainly formed at late endosomes in a NGF-dependent manner (By similarity). Interacts with RAPGEF2; the interaction occurs before or after nerve growth factor (NGF) stimulation (By similarity). Interacts (via PDZ domain) with KIDINS220 (via C-terminal domain) (By similarity). Interacts with IGSF9 and HTR4 (PubMed:15466885, PubMed:15340156). Interacts with DLL1 (PubMed:15509766). Found in a complex with IGSF9B and NLGN2; the interaction with IGSF9B is mediated via the PDZ 5 and PDZ 6 domains, while the interaction with NLGN2 is mediated via the WW1, WW2 and PDZ2 domains (PubMed:23751499). Interacts (via PDZ 6 domain) with USH1G (via SAM domain); the interaction is triggered by phosphorylation of USH1G by CK2 and negatively regulates MAGI2-mediated endocytosis (PubMed:24608321). Localized diffusely in the cytoplasm before nerve growth factor (NGF) stimulation. Recruited to late endosomes after NGF stimulation. Membrane-associated in synaptosomes (By similarity). Expressed throughout the retina except in the nuclear layers and the photoreceptor outer segments (at protein level) (PubMed:24608321). Highest retinal expression is observed in the outer plexiform layer, the outer limiting membrane and the inner segment of photoreceptor cells (at protein level) (PubMed:24608321). Expressed in brain. Major. May be due to an intron retention. Belongs to the MAGUK family.