Université Paul Cézanne (Aix-Marseille 3), CNRS UMR 6231, INRA USC 2027, Interactions Moléculaires et Systèmes Membranaires, Faculté des Sciences Saint-Jérôme, 13013 Marseille, France.
J Mol Biol. 2011 May 13;408(4):654-69. doi: 10.1016/j.jmb.2011.03.009. Epub 2011 Mar 17.
Cell surface glycosphingolipids (GSLs) including gangliosides play a key role in the regulation of the conformation, oligomerization, and fibrillation of amyloidogenic proteins. Correspondingly, most amyloidogenic proteins possess a functional GSL-binding motif (GBM). Sequence alignments of GSL-binding proteins against the GBM of α-synuclein allowed the establishment of a consensus GBM sequence defined as K/H/R/-X(1-4)-Y/F-X(4-5)-K/H/R, where at least one of the X(1-4) residues is glycine. The GBMs of α-synuclein (34-KEGVLYVGSKTK-45) and Alzheimer's disease β-amyloid peptide (Aβ) (5-RHDSGYEVHHQK-16) consist of a structurally related loop centered on tyrosine (Y39 for α-synuclein, Y10 for Aβ). Surface pressure measurements of GSL monolayers at the air-water interface allowed us to determine the following order for α-synuclein-GSL interactions: GM3>Gb3>GalCer-NFA>GM1>sulfatide>GalCer-HFA>LacCer>GM4>GM2>asialo-GM1>GD3, indicating a marked preference for GSLs with one, three, or five sugar units. The insertion of α-synuclein into sphingomyelin-containing monolayers was strongly stimulated by the presence of GM3. This effect was not observed with phosphatidylcholine monolayers, suggesting that the ganglioside facilitated the insertion of α-synuclein into raft-like membrane domains. Molecular dynamics simulations suggested that the side chain of Y39 was deeply inserted between GM3 head groups. Monolayer experiments with mutant GBM peptides showed that Y39, K34, and K45 were important for GM3 binding, whereas only Y39 appeared critical for GM1 recognition. The interaction of Aβ 5-16 with GM1 involved R5, H13, H14, and K16, but not Y10. These data indicate that subtle amino acid variations in the consensus GBM of α-synuclein and Aβ conferred distinct GSL-binding properties.
细胞表面糖脂（GSLs）包括神经节苷脂，在调节淀粉样蛋白构象、寡聚化和纤维形成方面发挥着关键作用。相应地，大多数淀粉样蛋白具有功能性 GSL 结合基序（GBM）。对 GSL 结合蛋白与α-突触核蛋白 GBM 的序列比对，确立了一个共识 GBM 序列，定义为 K/H/R/-X(1-4)-Y/F-X(4-5)-K/H/R，其中至少一个 X(1-4)残基为甘氨酸。α-突触核蛋白（34-KEGVLYVGSKTK-45）和阿尔茨海默病β-淀粉样肽（Aβ）（5-RHDSGYEVHHQK-16）的 GBM 由一个以酪氨酸（α-突触核蛋白的 Y39，Aβ 的 Y10）为中心的结构相关环组成。在气-水界面处对 GSL 单层的表面压力测量使我们能够确定α-突触核蛋白-GSL 相互作用的以下顺序：GM3>Gb3>GalCer-NFA>GM1>硫酸脑苷脂>GalCer-HFA>LacCer>GM4>GM2>无唾液酸-GM1>GD3，表明对具有一个、三个或五个糖单位的 GSL 具有明显的偏好。GM3 的存在强烈刺激了α-突触核蛋白插入含有神经鞘氨醇的单层。在磷脂酰胆碱单层中没有观察到这种效应，这表明神经节苷脂促进了α-突触核蛋白插入筏状膜结构域。分子动力学模拟表明，Y39 的侧链被深深插入 GM3 头基之间。用突变 GBM 肽进行的单层实验表明，Y39、K34 和 K45 对 GM3 结合很重要，而只有 Y39 似乎对 GM1 识别很关键。Aβ 5-16 与 GM1 的相互作用涉及 R5、H13、H14 和 K16，但不涉及 Y10。这些数据表明，α-突触核蛋白和 Aβ 的共识 GBM 中的细微氨基酸变化赋予了它们不同的 GSL 结合特性。
