Exosomes in Amyloid Propagation-Roles in Neurodegeneration

Extracellular vesicle (EVs)-mediated cell-to-cell communication is crucial for cell growth, signaling, and metabolism. Exosomes are a subtype of EVs originating from endosomal cellular machinery and have a relatively smaller size (30-150 nM). They carry nucleic acids, proteins, miRNA, lipids, metabolites, and growth factors, making them an exciting research tool for understanding the pathophysiology of complex human diseases. Different brain cells also communicate with themselves by the release of exosomes which helps in overall brain growth and in cell signaling. Recent studies have highlighted the importance of exosomes in neurodegenerative diseases (NDDs) of Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), prion, and Huntington's disease (HD). Exosomes are involved in the spread of amyloid-like protein aggregates formed in these diseases, but a comprehensive understanding of this spread mechanism is limited. In this article, we have analyzed the roles of exosomes in the spread of amyloid protein aggregates in the NDDs. Furthermore, we have discussed possible measures to address several gaps in our current understanding of cross talks between exosomes and protein aggregates in neurodegenerative disorders (NDDs). We have also discussed the therapeutic opportunities to delay or prevent pathogenic amyloid aggregate spread by exploiting exosomal transport. Overall, the review will contribute to develop a better understanding vesicular transport of amyloids and will help contend their propagation in different NDDs.