Alzheimer's disease genetic mutation evokes ultrastructural alterations: Correlation to an intracellular Aβ deposition and the level of GSK-3β-P(Y216) phosphorylated form

Herein we demonstrate that PC12 cells, which overexpress human wild-type amyloid-β precursor protein (AβPPwt) or AβPP bearing double Swedish mutation (AβPPsw), reveal phenotype characteristic for Alzheimer's disease (AD). The examination of cell ultrastructure showed the presence of peptide aggregates within the cells, activation of endosomal–lysosomal system and extensive exocytosis. Furthermore, the autophagy induction was also characteristic hallmark of amyloid-β-induced cytotoxicity. Morphological changes were positively correlated with the extent of phosphorylated glycogen synthase kinase-3β (phospho-Tyr216-GSK-3β, GSK-3β-P(Y216)). The activity of GSK-3β is believed to cause tau protein hyper-phosphorylation, increased amyloid-β production and local plaque-associated microglial-mediated inflammatory responses. All of them are symptomatic for AD. In our studies, the highly significant Y216 phosphorylation and over-expression of total GSK-3β were observed in AβPPsw-transfected PC12 cells. In addition, the immuocytochemical analysis showed co-localization of GSK-3β-P(Y216) and amyloid-β deposits. Thus, our data support a functional role of GSK-3β in AβPP processing, further implicating this kinase in the amyloid-β-dependent pathogenesis.