RESUMEN
Generation and accumulation of amyloid-ß (Aß) protein in the brain are the primary causes of Alzheimer's disease (AD). Alcadeins (Alcs composed of Alcα, Alcß and Alcγ family) are a neuronal membrane protein that is subject to proteolytic processing, as is Aß protein precursor (APP), by APP secretases. Previous observations suggest that Alcs are involved in the pathophysiology of Alzheimer's disease (AD). Here, we generated new mouse AppNL-F (APP-KI) lines with either Alcα- or Alcß-deficient background and analyzed APP processing and Aß accumulation through the aging process. The Alcα-deficient APP-KI (APP-KI/Alcα-KO) mice enhanced brain Aß accumulation along with increased amyloidogenic ß-site cleavage of APP through the aging process whereas Alcß-deficient APP-KI (APP-KI/Alcß-KO) mice neither affected APP metabolism nor Aß accumulation at any age. More colocalization of APP and BACE1 was observed in the endolysosomal pathway in neurons of APP-KI/Alcα-KO mice compared to APP-KI and APP-KI/Alcß-KO mice. These results indicate that Alcα plays an important role in the neuroprotective function by suppressing the amyloidogenic cleavage of APP by BACE1 in the brain, which is distinct from the neuroprotective function of Alcß, in which p3-Alcß peptides derived from Alcß restores the viability in neurons impaired by toxic Aß.