Proteomic profiling and biological characterization of extracellular vesicles isolated from Alzheimer\'s disease brain tissues

Introduction: Extracellular vesicles (EVs) isolated from human biospecimens contains AD pathogenic molecules, such as Abeta and tau, may play a role in the spread of disease in human brain. There is no comprehensive characterization of the molecules in human tissue-derived EVs. We therefore examined the protein composition of EVs isolated from the human brain tissue from patients with AD and an age- and sex-matched control group (CTRL). Methods: EVs were isolated from the cortical grey matter of AD (n=20) and Control (n=18). Tau and Amyloid beta (Aβ) in the EVs were measured by immunoassay. Differentially expressed EV proteins were observed by quantitative proteomics employing machine learning. Results: The levels of pS396 tau and Aβ were significantly enriched in AD EVs. Proteomic profiling shows enrichment of neuron-specific molecules in control EVs, and glial cell type-specific molecules in AD EVs. Machine learning approach of training group identified annexin A5 (ANXA5), neurosecretory protein VGF, neuronal membrane glycoprotein M6-a (GPM6A), and alpha-centractin (ACTZ) as most distincive molecules in AD EVs compared to the CTRLs. Each of the proteins were confirmed with 88% accuracy in testing group. Discussion: These data posit that in addition to Aβ and tau, the protein levels of ANXA5, VGF, GPM6A, and ACTZ are significantly altered in AD brain-derived EVs.