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Exosomes neutralize synaptic-plasticity-disrupting activity of Aβ assemblies in vivo.

An K, Klyubin I, Kim Y, Jung JH, Mably AJ, O'Dowd ST, Lynch T, Kanmert D, Lemere CA, Finan GM, Park JW, Kim TW, Walsh DM, Rowan MJ, Kim JH - Mol Brain (2013)

Bottom Line: We here provide in vivo evidence that exosomes derived from N2a cells or human cerebrospinal fluid can abrogate the synaptic-plasticity-disrupting activity of both synthetic and AD brain-derived Aβ.Mechanistically, this effect involves sequestration of synaptotoxic Aβ assemblies by exosomal surface proteins such as PrPC rather than Aβ proteolysis.These data suggest that exosomes can counteract the inhibitory action of Aβ, which contributes to perpetual capability for synaptic plasticity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Life Sciences, Pohang University of Science and Technology (POSTECH), Pohang, Gyungbuk 790-784, Korea. joungkim@postech.ac.kr.

ABSTRACT

Background: Exosomes, small extracellular vesicles of endosomal origin, have been suggested to be involved in both the metabolism and aggregation of Alzheimer's disease (AD)-associated amyloid β-protein (Aβ). Despite their ubiquitous presence and the inclusion of components which can potentially interact with Aβ, the role of exosomes in regulating synaptic dysfunction induced by Aβ has not been explored.

Results: We here provide in vivo evidence that exosomes derived from N2a cells or human cerebrospinal fluid can abrogate the synaptic-plasticity-disrupting activity of both synthetic and AD brain-derived Aβ. Mechanistically, this effect involves sequestration of synaptotoxic Aβ assemblies by exosomal surface proteins such as PrPC rather than Aβ proteolysis.

Conclusions: These data suggest that exosomes can counteract the inhibitory action of Aβ, which contributes to perpetual capability for synaptic plasticity.

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Related in: MedlinePlus

ADDLs bound to exosomes. (A) Immunoblots of ADDLs after incubation either with PBS or exosomes (left top). Exosomes present in each lane were verified with Flotillin-1 (left bottom). Right, relative optical density (O.D.) of Aβ species. (B) Immunoblot results of in vitro binding assay of Aβ and exosomes (left top). Either exosomes or ADDLs alone were loaded as controls. Left bottom, exosomes were also verified with an exosomal marker Flotillin-1 (P, pellet; S, supernatant). Right, relative O.D. of pelleted Aβ. (C) Exosome-bound ADDLs remained accessible to digestion by trypsin (left top). Limited proteolysis with trypsin resulted in cleavage of exosomal surface protein PrPC, but not the intraluminal protein Alix (left, middle and bottom). Very low amount of ADDLs remained after trypsin treatment and the levels of which were similar irrespective of the presence or absence of exosomes (right, relative O.D. of Aβ). Error bars, ± SEM. Statistical significance was expressed as *, P < 0.05; **, P < 0.01.
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Figure 3: ADDLs bound to exosomes. (A) Immunoblots of ADDLs after incubation either with PBS or exosomes (left top). Exosomes present in each lane were verified with Flotillin-1 (left bottom). Right, relative optical density (O.D.) of Aβ species. (B) Immunoblot results of in vitro binding assay of Aβ and exosomes (left top). Either exosomes or ADDLs alone were loaded as controls. Left bottom, exosomes were also verified with an exosomal marker Flotillin-1 (P, pellet; S, supernatant). Right, relative O.D. of pelleted Aβ. (C) Exosome-bound ADDLs remained accessible to digestion by trypsin (left top). Limited proteolysis with trypsin resulted in cleavage of exosomal surface protein PrPC, but not the intraluminal protein Alix (left, middle and bottom). Very low amount of ADDLs remained after trypsin treatment and the levels of which were similar irrespective of the presence or absence of exosomes (right, relative O.D. of Aβ). Error bars, ± SEM. Statistical significance was expressed as *, P < 0.05; **, P < 0.01.

Mentions: To address possible mechanisms underlying the protective action of exosomes against ADDL-induced LTP inhibition, we first examined whether exosomes degrade Aβ, which could abrogate the plasticity-disrupting effect. When we incubated ADDLs with exosomes in the same ratio used for LTP experiments, this resulted in a loss of the Aβ species that migrated at ~4 kDa (monomer) on SDS-PAGE (32 ± 13%, P < 0.01, n = 5, Mann-Whitney U test; Figure 3A). Unlike Aβ monomer, Aβ oligomers were largely unaffected by the incubation with exosomes (~12 kDa Aβ, 96 ± 10%, P > 0.5; ~16 kDa Aβ, 97 ± 5%, P > 0.05, n = 5, Mann-Whitney U test; Figure 3A), indicating that exosomes did not effectively degrade Aβ oligomers at least over the time course of our experiments. Although the reason for the loss of Aβ monomer is unclear, it could result from the degradation of authentic Aβ monomer by exosomal proteases such as insulin-degrading enzyme (IDE) [15,21]. However, since monomeric Aβ does not inhibit LTP [22] and IDE is not believed to degrade plasticity-disrupting Aβ oligomers [23], such degradation would not be expected to contribute to the rescue of the ADDL-mediated block of LTP.


Exosomes neutralize synaptic-plasticity-disrupting activity of Aβ assemblies in vivo.

An K, Klyubin I, Kim Y, Jung JH, Mably AJ, O'Dowd ST, Lynch T, Kanmert D, Lemere CA, Finan GM, Park JW, Kim TW, Walsh DM, Rowan MJ, Kim JH - Mol Brain (2013)

ADDLs bound to exosomes. (A) Immunoblots of ADDLs after incubation either with PBS or exosomes (left top). Exosomes present in each lane were verified with Flotillin-1 (left bottom). Right, relative optical density (O.D.) of Aβ species. (B) Immunoblot results of in vitro binding assay of Aβ and exosomes (left top). Either exosomes or ADDLs alone were loaded as controls. Left bottom, exosomes were also verified with an exosomal marker Flotillin-1 (P, pellet; S, supernatant). Right, relative O.D. of pelleted Aβ. (C) Exosome-bound ADDLs remained accessible to digestion by trypsin (left top). Limited proteolysis with trypsin resulted in cleavage of exosomal surface protein PrPC, but not the intraluminal protein Alix (left, middle and bottom). Very low amount of ADDLs remained after trypsin treatment and the levels of which were similar irrespective of the presence or absence of exosomes (right, relative O.D. of Aβ). Error bars, ± SEM. Statistical significance was expressed as *, P < 0.05; **, P < 0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
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getmorefigures.php?uid=PMC4222117&req=5

Figure 3: ADDLs bound to exosomes. (A) Immunoblots of ADDLs after incubation either with PBS or exosomes (left top). Exosomes present in each lane were verified with Flotillin-1 (left bottom). Right, relative optical density (O.D.) of Aβ species. (B) Immunoblot results of in vitro binding assay of Aβ and exosomes (left top). Either exosomes or ADDLs alone were loaded as controls. Left bottom, exosomes were also verified with an exosomal marker Flotillin-1 (P, pellet; S, supernatant). Right, relative O.D. of pelleted Aβ. (C) Exosome-bound ADDLs remained accessible to digestion by trypsin (left top). Limited proteolysis with trypsin resulted in cleavage of exosomal surface protein PrPC, but not the intraluminal protein Alix (left, middle and bottom). Very low amount of ADDLs remained after trypsin treatment and the levels of which were similar irrespective of the presence or absence of exosomes (right, relative O.D. of Aβ). Error bars, ± SEM. Statistical significance was expressed as *, P < 0.05; **, P < 0.01.
Mentions: To address possible mechanisms underlying the protective action of exosomes against ADDL-induced LTP inhibition, we first examined whether exosomes degrade Aβ, which could abrogate the plasticity-disrupting effect. When we incubated ADDLs with exosomes in the same ratio used for LTP experiments, this resulted in a loss of the Aβ species that migrated at ~4 kDa (monomer) on SDS-PAGE (32 ± 13%, P < 0.01, n = 5, Mann-Whitney U test; Figure 3A). Unlike Aβ monomer, Aβ oligomers were largely unaffected by the incubation with exosomes (~12 kDa Aβ, 96 ± 10%, P > 0.5; ~16 kDa Aβ, 97 ± 5%, P > 0.05, n = 5, Mann-Whitney U test; Figure 3A), indicating that exosomes did not effectively degrade Aβ oligomers at least over the time course of our experiments. Although the reason for the loss of Aβ monomer is unclear, it could result from the degradation of authentic Aβ monomer by exosomal proteases such as insulin-degrading enzyme (IDE) [15,21]. However, since monomeric Aβ does not inhibit LTP [22] and IDE is not believed to degrade plasticity-disrupting Aβ oligomers [23], such degradation would not be expected to contribute to the rescue of the ADDL-mediated block of LTP.

Bottom Line: We here provide in vivo evidence that exosomes derived from N2a cells or human cerebrospinal fluid can abrogate the synaptic-plasticity-disrupting activity of both synthetic and AD brain-derived Aβ.Mechanistically, this effect involves sequestration of synaptotoxic Aβ assemblies by exosomal surface proteins such as PrPC rather than Aβ proteolysis.These data suggest that exosomes can counteract the inhibitory action of Aβ, which contributes to perpetual capability for synaptic plasticity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Life Sciences, Pohang University of Science and Technology (POSTECH), Pohang, Gyungbuk 790-784, Korea. joungkim@postech.ac.kr.

ABSTRACT

Background: Exosomes, small extracellular vesicles of endosomal origin, have been suggested to be involved in both the metabolism and aggregation of Alzheimer's disease (AD)-associated amyloid β-protein (Aβ). Despite their ubiquitous presence and the inclusion of components which can potentially interact with Aβ, the role of exosomes in regulating synaptic dysfunction induced by Aβ has not been explored.

Results: We here provide in vivo evidence that exosomes derived from N2a cells or human cerebrospinal fluid can abrogate the synaptic-plasticity-disrupting activity of both synthetic and AD brain-derived Aβ. Mechanistically, this effect involves sequestration of synaptotoxic Aβ assemblies by exosomal surface proteins such as PrPC rather than Aβ proteolysis.

Conclusions: These data suggest that exosomes can counteract the inhibitory action of Aβ, which contributes to perpetual capability for synaptic plasticity.

Show MeSH
Related in: MedlinePlus