Université Paul Cézanne (Aix-Marseille 3), Université de la Méditerranée (Aix-Marseille 2), Centre de Recherche en Neurobiologie et Neurophysiologie de Marseille, CNRS UMR 6231, INRA USC 2027, Interactions Moléculaires et Systèmes Membranaires, Faculté des Sciences Saint-Jérôme, Marseille, France.
PLoS One. 2010 Feb 5;5(2):e9079. doi: 10.1371/journal.pone.0009079.
Membrane lipids play a pivotal role in the pathogenesis of Alzheimer's disease, which is associated with conformational changes, oligomerization and/or aggregation of Alzheimer's beta-amyloid (Abeta) peptides. Yet conflicting data have been reported on the respective effect of cholesterol and glycosphingolipids (GSLs) on the supramolecular assembly of Abeta peptides. The aim of the present study was to unravel the molecular mechanisms by which cholesterol modulates the interaction between Abeta(1-40) and chemically defined GSLs (GalCer, LacCer, GM1, GM3). Using the Langmuir monolayer technique, we show that Abeta(1-40) selectively binds to GSLs containing a 2-OH group in the acyl chain of the ceramide backbone (HFA-GSLs). In contrast, Abeta(1-40) did not interact with GSLs containing a nonhydroxylated fatty acid (NFA-GSLs). Cholesterol inhibited the interaction of Abeta(1-40) with HFA-GSLs, through dilution of the GSL in the monolayer, but rendered the initially inactive NFA-GSLs competent for Abeta(1-40) binding. Both crystallographic data and molecular dynamics simulations suggested that the active conformation of HFA-GSL involves a H-bond network that restricts the orientation of the sugar group of GSLs in a parallel orientation with respect to the membrane. This particular conformation is stabilized by the 2-OH group of the GSL. Correspondingly, the interaction of Abeta(1-40) with HFA-GSLs is strongly inhibited by NaF, an efficient competitor of H-bond formation. For NFA-GSLs, this is the OH group of cholesterol that constrains the glycolipid to adopt the active L-shape conformation compatible with sugar-aromatic CH-pi stacking interactions involving residue Y10 of Abeta(1-40). We conclude that cholesterol can either inhibit or facilitate membrane-Abeta interactions through fine tuning of glycosphingolipid conformation. These data shed some light on the complex molecular interplay between cell surface GSLs, cholesterol and Abeta peptides, and on the influence of this molecular ballet on Abeta-membrane interactions.
膜脂在阿尔茨海默病的发病机制中起着关键作用，其与阿尔茨海默病β-淀粉样肽（Abeta）的构象变化、寡聚化和/或聚集有关。然而，关于胆固醇和糖脂（GSL）对 Abeta 肽的超分子组装的各自影响，已有相互矛盾的数据报道。本研究旨在揭示胆固醇调节 Abeta（1-40）与化学定义的 GSL（GalCer、LacCer、GM1、GM3）之间相互作用的分子机制。使用 Langmuir 单层技术，我们表明 Abeta（1-40）选择性地结合在神经酰胺骨架酰链中含有 2-OH 基团的 GSL（HFA-GSL）。相比之下，Abeta（1-40）不与含有非羟化脂肪酸（NFA-GSL）的 GSL 相互作用。胆固醇通过在单层中稀释 GSL，抑制 Abeta（1-40）与 HFA-GSL 的相互作用，但使最初无活性的 NFA-GSL 能够与 Abeta（1-40）结合。晶体学数据和分子动力学模拟均表明，HFA-GSL 的活性构象涉及氢键网络，该网络限制了 GSL 糖基在与膜平行的方向上的取向。这种特殊的构象由 GSL 的 2-OH 基团稳定。相应地，Abeta（1-40）与 HFA-GSL 的相互作用受到 NaF 的强烈抑制，NaF 是氢键形成的有效竞争者。对于 NFA-GSL，是胆固醇的 OH 基团限制了糖脂采用与 Abeta（1-40）的 Y10 残基的糖-芳族 CH-π 堆积相互作用相容的活性 L 形构象。我们得出结论，胆固醇可以通过精细调节糖脂构象来抑制或促进膜-Abeta 相互作用。这些数据阐明了细胞表面 GSL、胆固醇和 Abeta 肽之间复杂的分子相互作用，以及这种分子芭蕾对 Abeta-膜相互作用的影响。
