Research School of Chemistry , The Australian National University , Canberra , ACT 2601 , Australia.
ACS Chem Neurosci. 2019 Mar 20;10(3):1668-1678. doi: 10.1021/acschemneuro.8b00586. Epub 2018 Dec 17.
The endogenous lipids N-arachidonylglycine and oleoyl-l-carnitine are potential therapeutic leads in the treatment of chronic pain through their inhibition of the glycine transporter GlyT2. However, their mechanism of action is unknown. It has been hypothesized that these "bioactive" lipids either inhibit GlyT2 indirectly, by significantly perturbing the biophysical properties of the membrane, or directly, by binding directly to the transporter (either from a membrane-exposed or solvent-exposed binding site). Here, we used molecular dynamics simulations to study the effects of the lipids anandamide, N-arachidonylglycine, and oleoyl-l-carnitine on (a) the biophysical properties of the bilayer and (b) direct binding interactions with GlyT2. During the simulations, the biophysical properties of the bilayer itself, for example, the area per lipid, bilayer thickness, and order parameters, were not significantly altered by the presence or type of bioactive lipid, regardless of the presence of GlyT2. Our work, together with previous computational and experimental data, suggests that these acyl-inhibitors of GlyT2 inhibit the transporter by directly binding to it. However, these bioactive lipids bound to various parts of GlyT2 and did not prefer a single binding site during 4.5 μs of simulation. We postulate that the binding site is located at the solvent-exposed regions of GlyT2. Understanding the mechanism of action of these and related bioactive lipids is essential in effectively developing high-affinity GlyT2 inhibitors for the treatment of pain.
内源性脂质 N-花生四烯酰基甘氨酸和油酰基左旋肉碱通过抑制甘氨酸转运蛋白 GlyT2 成为治疗慢性疼痛的潜在治疗靶点。然而，它们的作用机制尚不清楚。据推测，这些“生物活性”脂质通过显著改变膜的物理特性，间接抑制 GlyT2，或者通过直接与转运蛋白结合（来自膜暴露或溶剂暴露的结合位点）来直接抑制 GlyT2。在这里，我们使用分子动力学模拟来研究脂质大麻素、N-花生四烯酰基甘氨酸和油酰基左旋肉碱对（a）双层的物理特性和（b）与 GlyT2 的直接结合相互作用的影响。在模拟过程中，双层本身的物理特性，例如每个脂质的面积、双层厚度和序参数，不受生物活性脂质的存在或类型的显著影响，无论是否存在 GlyT2。我们的工作与以前的计算和实验数据一起表明，这些 GlyT2 的酰基抑制剂通过直接与转运蛋白结合来抑制转运蛋白。然而，这些生物活性脂质结合到 GlyT2 的不同部位，在 4.5 μs 的模拟过程中并没有优先选择一个单一的结合位点。我们假设结合位点位于 GlyT2 的溶剂暴露区域。了解这些和相关生物活性脂质的作用机制对于有效开发用于治疗疼痛的高亲和力 GlyT2 抑制剂至关重要。
