Postsynaptic MAGUK scaffold protein that links CADM1 cell adhesion molecules to core components of the postsynaptic density (By similarity). In CA1 pyramidal neurons, required for synaptic KCNN2- containing channel function and long-term potentiation expression (By similarity). Seems to negatively regulate SRC function in epithelial cells (PubMed:19665017). {ECO:0000250|UniProtKB:D3ZAA9, ECO:0000250|UniProtKB:Q9WV34, ECO:0000269|PubMed:19665017}. This is the function of ENSG00000108852 (MPP2, MAGUK p55 scaffold protein 2).