C terminus of presenilin is required for overproduction of amyloidogenic Aβ42 through stabilization and endoproteolysis of presenilin

Mutations in presenilin (PS) genes cause early onset familial Alzheimer's disease (FAD) by increasing production of the amyloidogenic form of amyloid beta peptides ending at residue 42 (A beta 42). To identify a PS subdomain responsible for overproduction of A beta 42, we analyzed neuro2a cell lines expressing modified forms of PS2 that harbor an N141I FAD mutation. Deletion or addition of amino acids at the C terminus and Ile448 substitution in PS2 with the N141I FAD mutation abrogated the increase in Ab42 secretion, and Ab42 overproduction was dependent on the stabilization and endoproteolysis of PS2. The same C-terminal modifications in PS1 produced similar effects. Hence, we suggest that the C terminus of PS plays a crucial role in the overproduction of A beta 42 through stabilization of endoproteolytic PS derivatives and that these derivatives may be the pathologically active species of PS that cause FAD.