Talk title The synaptic pathology of Alzheimer’s disease: focusing on patient brains
Speaker Prof. Hwan-Ching TAI
Associate Professor
Department of Chemistry, Taiwan University
Date & Time 27 November 2017 (Thursday) 15:30-16:30
Venue Room G004, E12 Building (University of Macau)
Abstract Alzheimer’s disease (AD) is an amyloid-induced neurodegenerative tauopathy, and one of the greatest medical challenges of our aging societies. Despite tens of billions of US dollars invested, there has been no clinical success in the development of AD therapeutics over the past two decades. This reflects our over-reliance of research based on transgenic mouse disease models, while the actual pathogenic processes in patient brains remain understudied.

Therefore our laboratory focused on developing new technical platforms for investigating the synaptic pathology of AD patients, using synaptosomes prepared from postmortem brain tissues. The first platform is to capture synaptosomes over glass slides for immunofluorescence imaging. This allowed us to identify the presence of hyperphosphorylated tau oligomers in both presynaptic and postsynaptic terminals of AD subjects. Further improvements in fixation and capture methods facilitated the imaging of synaptosomes using three-color direct stochastic optical reconstruction microscopy (dSTORM). We managed to visualize tau, synaptophysin, and PSD-95 with 30 nm resolution in synaptosomes. The mechanism of tau hyperphosphorylation was investigated by phosphoproteomics approach in APP/PS1 mice, based on shotgun mass spectrometry and label-free quantification. The early sites of tau hyperphosphorylation induced by β-amyloid (Aβ) turned out to be S199, S202, S396, S400, and S404. These sites appear to be regulated by the activity of cyclin-dependent kinase 5 (CDK5). For metabolomics characterization of synaptosomes, we are devising new amine-reactive isotope tags for multiplex quantitation. Lastly, we have optimized the flow cytometry analysis of synaptosomes, achieving three-color immunofluorescence characterization. Individual synaptosomes could be collected by fluorescence-activated sorting to yield highly purified fractions suitable for transcriptomics studies using next-generation sequencing. This will help us identify mRNAs localized to synaptic terminals, the translation of which are critical for synaptic function and modulation. Changes in synaptic mRNAs will have important implications for understanding synaptic plasticity, learning and memory, drug addiction, and synaptic pathology in various neurological disorders including AD.