title: Accelerated release of exosome-associated GM1 ganglioside (GM1) by endocytic pathway abnormality: another putative pathway for GM1-induced amyloid fibril formation.
abstract: Exosomes are extracellularly released small vesicles that are derived from multivesicular bodies formed via the endocytic pathway. We treated pheochromocytoma PC12 cells with chloroquine, an acidotropic agent, which potently perturbs membrane trafficking from endosomes to lysosomes. Chloroquine treatment increased the level of GM1 ganglioside in cell media only when the cells were exposed to KCl for depolarization, which is known to enhance exosome release from neurons. In the sucrose-density-gradient fractionation of cell media, GM1 ganglioside was exclusively recovered with Alix, a specific marker of exosomes, in the fractions with the density corrresponding to that of exosomes. Notably, amyloid-beta assembly was markedly accelerated when incubated with the exosome fraction prepared from the culture media of PC12 cells treated with chloroquine and KCl. Furthermore, amyloid-beta assembly was significantly suppressed by the co-incubation with an antibody specific to GM1-bound amyloid-beta, an endogenous seed for amyloid formation of Alzheimer's disease. Together with our previous finding that chloroquine treatment induces the accumulation of GM1 ganglioside in early endosomes, results of this study suggest that endocytic pathway abnormality accelerates the release of exosome-associated GM1 ganglioside following its accumulation in early endosomes. Furthermore, this study also suggests that extracellular amyloid fibril formation is induced by not only GM1 gangliosides accumulated on the surface of the cells but also those released in association with exosomes.
authors.affiliation: Department of Alzheimer's Disease Research, National Institute for Longevity Sciences, National Center for Geriatrics and Gerontology, Obu, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Yuyama
authors.forename: Naoki
authors.initials: N
authors.lastname: Yamamoto
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Yanagisawa
mesh_terms: D016229:Amyloid beta-Peptides / Q000378:metabolism; D000818:Animals; D052160:Benzothiazoles; D002118:Calcium / Q000378:metabolism; D002458:Cell Fractionation / Q000379:methods; D002738:Chloroquine / Q000494:pharmacology; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D005677:G(M1) Ganglioside / Q000378:metabolism*; D021962:Membrane Microdomains / Q000187:drug effects / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning / Q000379:methods; D008954:Models, Biological; D016716:PC12 Cells / Q000187:drug effects; D011189:Potassium Chloride / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D013844:Thiazoles / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D052160:Benzothiazoles; D013844:Thiazoles; C009462:thioflavin T; D005677:G(M1) Ganglioside; D011189:Potassium Chloride; D002738:Chloroquine; D002118:Calcium