Acceleration of α-synuclein aggregation by exosomes.
Bottom Line: The exosomes reduce the lag time indicating that they provide catalytic environments for nucleation.The catalytic effects of exosomes derived from naive cells and cells that overexpress α-synuclein do not differ.Using mass spectrometry, we found several phospholipid classes in the exosomes, including phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine, phosphatidylinositol, and the gangliosides GM2 and GM3.
Affiliation: From the Departments of Physical Chemistry.Show MeSH
Related in: MedlinePlus
Mentions: The size distribution in the exosome samples was determined using DLS and NTA. The main species in the DLS measurements, representing around 99% of the vesicles by number, was found to have a diameter around 100 nm, which is typical for exosomes (42), and the minor portion (<1%) has a considerably larger diameter (Fig. 1D). NTA showed similar results (Fig. 1E). The measured ζ potential for exosomes was similar to that obtained for small unilamellar vesicles (SUVs) with anionic lipids (Table 1). We can thus conclude that the exosomes are negatively charged. The cryo-TEM images of the exosomes show unilamellar, spherical vesicles with a diameter of 96 ± 8 (±S.E.), in agreement with the DLS and NTA measurements. Also, a fraction of larger exosomes was visible, with a diameter of 185 ± 35 nm (±S.E.). The membrane thickness was found to be 6 nm, which is typical for cell membranes (normally 4–10 nm) (43, 44). Exosomes from cells overexpressing human α-syn contain dark gray fields (Fig. 10A), which may represent protein or some other components of the exosomes. Additional exposure leads to blistering of these fields, further supporting a protein component. However, from these images alone, it is not possible to tell whether this is α-syn, another protein, or several proteins. The cryo-TEM images also show that the vesicles deform when they approach each other, consistent with electrostatic repulsion between the charged membranes.