APP and Alzheimer disease: Other proteins central to the biology of amyloid Beta (Aβ), a characteristic pathological feature of AD, include APP, SNCA, APCS, Pappalysin (PAPPA), Microtubule-associated protein tau (MAPT) and apolipoprotein E (apoE) and its alleles (apoE2, E3 and E4) and thus their levels were determined here.