Figure 2.

(A) Exosome structure and cargo. Exosomes are surrounded by a phospholipid bilayer and their content reflects the cell of origin. So besides to generic molecules that identify all exosomes as Tetraspanins, Lipid rafts, MVB formation proteins, membrane transport and fusion proteins, there are other molecules specific to their origin, as L1CAM for neural exosomes as well as proteins related to aging and neurological diseases such as β-amyloid, p-Tau, LRKK2, insulin receptor substrate 1 (IRS-1), a-synuclein, amyloid precursor protein (APP), TDP-43, depeptide protein repeats (DPRs) and many others. In addition, there is also a nucleic component consisting of DNA, mRNA and different kinds of non-coding RNAs (ncRNAs; miRNAs, lncRNAs, circRNAs, piwi-RNA, etc…). (B) Exosomes: a double-edged sword in neurodegenerative disease. Exosomes could favorite and/or trigger the spreading of the disease leading to neurodegeneration or they could sequester neuro-toxic components from neural cells protecting them.