PTK2B and Alzheimer disease: Fyn is also implicated in AD pathogenesis by transducing signals downstream of Amyloid-ß oligomer binding to PrPC/mGluR5 receptor complexes at the cell surface [29, 30, 52, 63–65] and by interaction with the GWAS risk gene, PTK2B (Pyk2) [20, 27, 34, 53].