The role of Alzheimer’s risk factor ApoE4 on intracellular Aβ aggregation

Abstract

AbstractBackgroundApolipoprotein E4 (ApoE4) is the main genetic risk factor for Alzheimer’s disease (AD). Previous research supports that ApoE4 increases amyloid‐β (Aβ) aggregation and plaque deposition. However, it remains poorly understood how ApoE4 affects the aggregation of Aβ prior to plaque seeding on a cellular level. The aim of this project is to use high‐resolution techniques to study intraneuronal Aβ accumulation at a synaptic and subcellular level and investigate how different ApoE isoforms influence this.MethodThe aggregation of Aβ in cultured primary neurons expressing human APP/Aβ will be studied using a correlative approach combining infrared spectroscopy and super‐resolution microscopy. Infrared spectroscopy allows us to study protein aggregation by looking at alterations in β‐sheet structures. Super‐resolution microscopy gives insights into the subcellular localization of Aβ and in changes in synaptic phenotypes. Human ApoE3 and ApoE4, derived from ApoE3 knock‐in (ApoE3‐KI) and ApoE4‐KI primary astrocyte cultures, are used as a physiological source to treat APP/Aβ primary neurons with human ApoE isoforms.ResultWe established an approach to obtain human ApoE3 and ApoE4 from primary mouse astrocytes and previously showed that Aβ and ApoE intersect inside neurons. In addition, we established a high‐resolution infrared spectroscopy approach for studying individual amyloid structures directly in neurons. In primary neurons generated from an human APP(NL‐F/NL‐F) knock‐in model we characterized the aggregation of intracellular Aβ and synaptic phenotypes with age. Additionally, an approach to supply primary neurons with human ApoE for longer time periods has been tested and allows to study chronic effects of human ApoE on Aβ aggregation inside neurons.ConclusionOur novel approach to study intraneuronal Aβ aggregation in cultured neurons potentially will contribute to new insights into where and how Aβ aggregates and will help to better understand how ApoE isoforms affect Aβ aggregation.