A Novel PSEN1 K311R Mutation Discovered in Chinese Families with Late-Onset Alzheimer’s Disease Affects Amyloid-β Production and Tau Phosphorylation

Abstract

Background: Presenilin-1 (PSEN1) is the most frequently mutated gene in familial Alzheimer’s disease (AD), whereas only several novel mutations have been reported in China and functional studies were seldom conducted.

Objective: We describe a novel PSEN1 K311R mutation in two Chinese families with late-onset AD and its functional impact on amyloid-β protein precursor (AβPP) processing and tau phosphorylation.

Methods: The mutation was detected by direct sequencing of PSEN1 exon 9. HEK293 cells stably expressing wild-type APP695 (HEK293-APP695_wt) were transfected with plasmids containing human wild-type PSEN1, PSEN1 K311R mutation, and PSEN1 E280A mutation to compare the K311R mutation’s effects on AβPP processing with other groups. In addition, each group of cells were co-transfected with plasmids harboring PSEN1 and human wild-type MAPT complementary DNA to study the mutation’s impacts on tau phosphorylation.

Results: The K311R mutation was detected in probands of two late-onset AD families. Expression of the K311R or E280A mutation increased amyloid-β (Aβ)₄₂ levels but decreased Aβ₄₀ levels, resulting in an overall increase in the Aβ₄₂/Aβ₄₀ ratio compared to those in wild-type PSEN1 transfected cells (p < 0.05). The K311R or E280A mutation also increased the levels of phosphorylated tau compared to wild-type PSEN1 (p < 0.05).

Conclusion: The K311R mutation might contribute to AD pathogenesis by overproducing toxic Aβ species and enhancing tau phosphorylation. Further in-depth studies are needed to decipher the pathogenic mechanisms of the K311R mutation in terms of AβPP cleavage, tau phosphorylation, and other presenilin-1 mediated functional pathways.