The Depolarization-Evoked, Ca2+-Dependent Release of Exosomes From Mouse Cortical Nerve Endings: New Insights Into Synaptic Transmission

Abstract

Whether exosomes can be actively released from presynaptic nerve terminals is a matter of debate. To address the point, mouse cortical synaptosomes were incubated under basal and depolarizing (25 mM KCl-enriched medium) conditions, and extracellular vesicles were isolated from the synaptosomal supernatants to be characterized by dynamic light scattering, transmission electron microscopy, Western blot, and flow cytometry analyses. The structural and biochemical analysis unveiled that supernatants contain vesicles that have the size and the shape of exosomes, which were immunopositive for the exosomal markers TSG101, flotillin-1, CD63, and CD9. The marker content increased upon the exposure of nerve terminals to the high-KCl stimulus, consistent with an active release of the exosomes from the depolarized synaptosomes. High KCl-induced depolarization elicits the Ca2+-dependent exocytosis of glutamate. Interestingly, the depolarization-evoked release of exosomes from cortical synaptosomes also occurred in a Ca2+-dependent fashion, since the TSG101, CD63, and CD9 contents in the exosomal fraction isolated from supernatants of depolarized synaptosomes were significantly reduced when omitting external Ca2+ ions. Differently, (±)-baclofen (10 µM), which significantly reduced the glutamate exocytosis, did not affect the amount of exosomal markers, suggesting that the GABAB-mediated mechanism does not control the exosome release. Our findings suggest that the exposure of synaptosomes to a depolarizing stimulus elicits a presynaptic release of exosomes that occurs in a Ca2+-dependent fashion. The insensitivity to the presynaptic GABAB receptors, however, leaves open the question on whether the release of exosomes could be a druggable target for new therapeutic intervention for the cure of synaptopathies.

Lipopolysaccharide increases exosomes secretion from endothelial progenitor cells by toll‐like receptor 4 dependent mechanism

“…The Ca 2+ playes an important role in regulating the exosome secretion from MVBs (Butreddy et al., 2021; Gurunathan et al., 2021; Olivero et al., 2021,). To assess whether the LPS induced exosome release was associated with the change in intracellular Ca 2+ , we measured whether LPS can modify the intracellular Ca 2+ concentration ([Ca 2+ ] i ) of EPC.…”

“…Previous research has indicated that Ca 2+ is a key participant in the process of exosome release (Butreddy et al., 2021; Gurunathan et al., 2021; Olivero et al., 2021). The Ca 2+ may play a role as a messenger in the activation of exosome‐carrying cells to release these small vesicles at the proper site and time.…”

Presynaptic Release-Regulating Alpha2 Autoreceptors: Potential Molecular Target for Ellagic Acid Nutraceutical Properties

“…Finally, the binding free energies calculated by carrying out the MM/GBSA method, known to be one of the rigorous and efficient methods to predict relative binding affinities, has been useful for evaluating the strength of EA’s affinity over the α 2 -ARs binding pocket [ 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 ]. In this way, 1000 snapshots from 50 ns of MDs are extracted for the binding free energy calculations of both the α 2 -ARs-EA complex and the known partial agonist and antagonist in complex to α 2 -ARs [ 60 , 61 ].…”

“…Synaptosomes are pinched-off nerve terminals that contain structures (e.g., vesicles, mitochondria, endoplasmic reticulum, synthetic and enzymatic pathways, see Olivero et al, 2021 [ 52 ]) that are present in the neuronal processes they originate from, confirming their presynaptic origins. Synaptosomes can take up, synthesize, metabolize, store, and release transmitters, and possess naïve receptors and transporters, whose activation controls the synaptosomal functions, particularly transmitter exocytosis.…”

KCa3.1 promotes exosomes secretion by activating on AKT/Rab27a in atrial myocytes during rapid pacing

“…Ca 2+ handling abnormity promotes the secretion of exosomes has been reported earlier. Olivero et al found that the depolarization-evoked release of exosomes from cortical synaptosomes occurred in a Ca 2+ -dependent fashion [20] . Interestingly, physical stimuli such as high frequency acoustic stimulation also leads to calcium-dependent exosomes release [21] .…”