Proteomic analysis of the brain tissues from a transgenic mouse model of amyloid β oligomers

Amyloid β (Aβ) oligomers are presumed to be one of the causes of Alzheimer's disease (AD). Previously, we identified the E693Δ mutation in amyloid precursor protein (APP) in patients with AD who displayed almost no signals of amyloid plaques in amyloid imaging. We generated APP-transgenic mice expressing the E693Δ mutation and found that they possessed abundant Aβ oligomers from 8months of age but no amyloid plaques even at 24months of age, indicating that these mice are a good model to study pathological effects of Aβ oligomers. To elucidate whether Aβ oligomers affect proteome levels in the brain, we examined the proteins and phosphoproteins for which levels were altered in 12-month-old APP(E693Δ)-transgenic mice compared with age-matched non-transgenic littermates. By two-dimensional gel electrophoresis (2DE) followed by staining with SYPRO Ruby and Pro-Q Diamond and subsequent mass spectrometry techniques, we identified 17 proteins and 3 phosphoproteins to be significantly changed in the hippocampus and cerebral cortex of APP(E693Δ)-transgenic mice. Coactosin like-protein, SH3 domain-bind glutamic acid-rich-like protein 3 and astrocytic phosphoprotein PEA-15 isoform 2 were decreased to levels less than 0.6 times those of non-transgenic littermates, whereas dynamin, profilin-2, vacuolar adenosine triphosphatase and creatine kinase B were increased to levels more than 1.5 times those of non-transgenic littermates. Furthermore, 2DE Western Blotting validated the changed levels of dynamin, dihydropyrimidinase-related protein 2 (Dpysl2), and coactosin in APP(E693Δ)-transgenic mice. Glyoxalase and isocitrate dehydrogenase were increased to levels more than 1.5 times those of non-transgenic littermates. The identified proteins could be classified into several groups that are involved in regulation of different cellular functions, such as cytoskeletal and their interacting proteins, energy metabolism, synaptic component, and vesicle transport and recycling. These findings indicate that Aβ oligomers altered the levels of some proteins and phosphoproteins in the hippocampus and cerebral cortex, which could illuminate novel therapeutic avenues for the treatment of AD.