Surface-induced phase separation of a sphingomyelin/cholesterol/ganglioside GM1-planar bilayer on mica surfaces and microdomain molecular conformation that accelerates Abeta oligomerization.
Ganglioside GM1 mediates the amyloid beta (Abeta) aggregation that is the hallmark of Alzheimer's disease (AD). To investigate how ganglioside-containing lipid bilayers interact with Abeta, we examined the interaction between Abeta40 and supported planar lipid bilayers (SPBs) on mica and SiO(2) substrates by using atomic force microscopy, fluorescence microscopy, and molecular dynamics computer simulations. These SPBs contained several compositions of sphingomyelin, cholesterol, and GM1 and were treated at physiological salt concentrations. Surprisingly high-speed Abeta aggregation of fibril formations occurred at all GM1 concentrations examined on the mica surface, but on the SiO(2) surface, only globular agglomerates formed and they formed slowly. At a GM1 concentration of 20mol%, unique triangular regions formed on the mica surface and the rapidly formed Abeta aggregations were observed only outside these regions. We have found that some unique surface-induced phase separations are induced by the GM1 clustering effects and the strong interactions between the GM1 head group and the water layer adsorbed in the ditrigonal cavities on the mica surface. The speed of Abeta40 aggregation and the shape of the agglomerates depend on the molecular conformation of GM1, which varies depending on the substrate materials. We identified the conformation that significantly accelerates Abeta40 aggregation, and we think that the detailed knowledge about the GM1 molecular conformation obtained in this work will be useful to those investigating Abeta-GM1 interactions.
Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan.
Yanli
Y
Mao
Zhiguo
Z
Shang
Yosuke
Y
Imai
Tyuji
T
Hoshino
Ryugo
R
Tero
Motohiko
M
Tanaka
Naoki
N
Yamamoto
Katsuhiko
K
Yanagisawa
Tsuneo
T
Urisu
D000538:Aluminum Silicates / Q000737:chemistry*; D000544:Alzheimer Disease / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002784:Cholesterol / Q000737:chemistry* / Q000378:metabolism; D003198:Computer Simulation; D005677:G(M1) Ganglioside / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D021962:Membrane Microdomains / Q000737:chemistry* / Q000378:metabolism; D055503:Protein Multimerization; D012822:Silicon Dioxide / Q000737:chemistry; D013109:Sphingomyelins / Q000737:chemistry* / Q000378:metabolism; D013552:Swine
D000538:Aluminum Silicates; D016229:Amyloid beta-Peptides; D013109:Sphingomyelins; D005677:G(M1) Ganglioside; D012822:Silicon Dioxide; D002784:Cholesterol; C011934:mica