On the mechanism of internalization of alpha-synuclein into microglia: roles of ganglioside GM1 and lipid raft.
ALpha-synuclein (alpha-syn) has been known to be a key player of the pathogenesis of Parkinson's disease and has recently been detected in extracellular biological fluids and shown to be rapidly secreted from cells. The penetration of alpha-syn into cells has also been observed. In this study, we observed that dl-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol, a glucosyltransferase inhibitor, and proteinase K inhibited the internalization of extracellular monomeric alpha-syn into BV-2 cells, and the addition of monosialoganglioside GM1 ameliorated the inhibition of alpha-syn internalization in dl-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol-treated BV-2 cells. Furthermore, inhibition of clathrin-, caveolae-, and dynamin-dependent endocytosis did not prevent the internalization of alpha-syn, but disruption of lipid raft inhibited it. Inhibition of macropinocytosis and disruption of actin and microtubule structures also did not inhibit the internalization of alpha-syn. In addition, we further confirmed these observations by co-culture system of BV-2 cells and alpha-syn-over-expressing SH-SY5Y cells. These findings suggest that extracellular alpha-syn is internalized into microglia via GM1 as well as hitherto-unknown protein receptors in clathrin-, caveolae-, and dynamin-independent, but lipid raft-dependent manner. Elucidation of the mechanism involved in internalization of alpha-syn should be greatly helpful in the development of new treatments of alpha-syn-related neurodegenerative diseases.
Park
Ji-Young
JY
Chronic Inflammatory Disease Research Center, Ajou University School of Medicine, Suwon, Korea.
Kim
Kwang Soo
KS
Lee
Saet-Byul
SB
Ryu
Jae-Sung
JS
Chung
Kwang Chul
KC
Choo
Young-Kug
YK
Jou
Ilo
I
Kim
Jongsun
J
Park
Sang Myun
SM
D000818:Animals; D022461:Caveolins / Q000187:drug effects / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D002966:Clathrin / Q000187:drug effects / Q000378:metabolism; D018920:Coculture Techniques; D034281:Dynamins / Q000187:drug effects / Q000378:metabolism; D004660:Encephalitis / Q000378:metabolism / Q000503:physiopathology; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D019286:Endopeptidase K / Q000378:metabolism / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005677:G(M1) Ganglioside / Q000378:metabolism* / Q000494:pharmacology; D005964:Glucosyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D019636:Neurodegenerative Diseases / Q000378:metabolism / Q000503:physiopathology; D010300:Parkinson Disease / Q000378:metabolism / Q000503:physiopathology; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D051844:alpha-Synuclein / Q000378:metabolism*
D022461:Caveolins; D002966:Clathrin; D004791:Enzyme Inhibitors; D051844:alpha-Synuclein; D005677:G(M1) Ganglioside; D005964:Glucosyltransferases; D019286:Endopeptidase K; D034281:Dynamins