Aß42 Protofibrils Interact with and Are Trafficked through MicroglialDerived Microvesicles

Microvesicles () and exosomes comprise a class of cell -secreted particles termed extracellular vesicles (EVs). These -holding vesicles mediate cell -to -cell communication and have recently been implicated in neurodegenerative diseases such as Alzheimer's disease (AD), The two types of EVs are distinguished by the mechanism of cell release and their size, with the smaller exosomes and the larger MVs ranging from 30 to 100 nm and 100 rim to 1 pm in diameter, respectively MV numbeis are increased in AD and appear to interact with arnyloid-fl peptide (A/3), the primary protein component of the neuritic plaques in the AD brain. Because-n cells play such an important o linked neuron) amnia on, we sought to characterize MVs shed from microglial better understand MV interactions with AA and determine whether internalized A/3 may be incorporated into secreted MVs. Multiple strategies were`used to characterize MVs shed from BV -2 microglia after ATP stimulation Confocal images of isolated MVs bound to fluorescently labeled annexin-V via externalized phosphatidylserine revealed a polydisperse population of small spherical structures. Dynamic light scattering measurements yielded MV diameters ranging from 1S0 to 600 nm. Electron.microscopy of -resin -embedded MVs cut into thin lices showed well-defined uranyl acetate -stained ring -like structures in a similar diameter range. The use of a fluorescently labeled membrane insertion probe, NBD C6 -1-4PC, effectively tracked MVs in binding experiments, and an A/3 ELISA confirmed a strong interaction between IVIVs and A/3 protofibrils but not A,13 monomers. 1)espite the lesser monomer interaction, MVs had an inhibitory effect on monomer aggregation. Primary microglia rapidly internalized Ni protofibrils, and subsequent stimulation of the microglia with ATP resulted in the release of MVs containing the internalized Al) protofibrils. The role of MVs in neurodegeneration and inflammation is an emerging area, and further knowledge of MV interaction with Afi may shed light on racellular spread and influence on neurotoxicity and neuroinflammation.