Exosomal tau with seeding activity is released from Alzheimer's disease synapses, and seeding potential is associated with amyloid beta

作者：Emily Miyoshi, Tina Bilousova, Mikhail Melnik, Danyl Fakhrutdinov, Wayne W. Poon, Harry V. Vinters, Carol A. Miller, María M. Corrada, Claudia H. Kawas, Ryan C. Bohannan, Chad A. Caraway, Chris Jean Elias, Katherine N. Maina, Jesus Campagna, Varghese John, Karen H. Gylys · 发表于：Laboratory Investigation · 年份：2021 · DOI：10.1038/s41374-021-00644-z · 被引用次数：61 · 研究领域：Alzheimer's disease research and treatments、Extracellular vesicles in disease、Lipid Membrane Structure and Behavior

Synaptic transfer of tau has long been hypothesized from the human pathology pattern and has been demonstrated in vitro and in vivo, but the precise mechanisms remain unclear. Extracellular vesicles such as exosomes have been suggested as a mechanism, but not all tau is exosomal. The present experiments use a novel flow cytometry assay to quantify depolarization of synaptosomes by KCl after loading with FM2-10, which induces a fluorescence reduction associated with synaptic vesicle release; the degree of reduction in cryopreserved human samples equaled that seen in fresh mouse synaptosomes. Depolarization induced the release of vesicles in the size range of exosomes, along with tetraspanin markers of extracellular vesicles. A number of tau peptides were released, including tau oligomers; released tau was primarily unphosphorylated and C-terminal truncated, with Aβ release just above background. When exosomes were immunopurified from release supernatants, a prominent tau band showed a dark smeared appearance of SDS-stable oligomers along with the exosomal marker syntenin-1, and these exosomes induced aggregation in the HEK tau biosensor assay. However, the flow-through did not seed aggregation. Size exclusion chromatography of purified released exosomes shows faint signals from tau in the same fractions that show a CD63 band, an exosomal size signal, and seeding activity. Crude synaptosomes from control, tauopathy, and AD cases demonstrated lower seeding in tauopathy compared ...