ABSTRACT
Accumulating evidence suggests that the abnormal aggregation of amyloid-ß (Αß) peptide in Alzheimer's disease (AD) begins intraneuronally, within vesicles of the endosomal-lysosomal pathway where Aß is both generated and degraded. Metalloproteases, including endothelin-converting enzyme (ECE)-1 and -2, reside within these vesicles and normally limit the accumulation of intraneuronally produced Aß. In this study, we determined whether disruption of Aß catabolism could trigger Aß aggregation within neurons and increase the amount of Aß associated with exosomes, small extracellular vesicles derived from endosomal multivesicular bodies. Using cultured cell lines, primary neurons, and organotypic brain slices from an AD mouse model, we found that pharmacological inhibition of the ECE family of metalloproteases increased intracellular and extracellular Aß levels and promoted the intracellular formation of Aß oligomers, a process that did not require internalization of secreted Aß. In vivo, the accumulation of intraneuronal Aß aggregates was accompanied by increased levels of both extracellular and exosome-associated Aß, including oligomeric species. Neuronal exosomes were found to contain both ECE-1 and -2 activities, suggesting that multivesicular bodies are intracellular sites of Aß degradation by these enzymes. ECE dysfunction could lead to the accumulation of intraneuronal Aß aggregates and their subsequent release into the extracellular space via exosomes.-Pacheco-Quinto, J., Clausen, D., Pérez-González, R., Peng, H., Meszaros, A., Eckman, C. B., Levy, E., Eckman, E. A. Intracellular metalloprotease activity controls intraneuronal Aß aggregation and limits secretion of Aß via exosomes.
