Department of Applied Chemistry in Bioscience, Graduate School of Agricultural Science, Faculty of Agriculture, Kobe University, Kobe, Japan; Department of Pharmacology, and Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California, USA.
Department of Pharmacology, and Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California, USA.
J Nutr Biochem. 2022 Dec;110:109129. doi: 10.1016/j.jnutbio.2022.109129. Epub 2022 Aug 15.
It is generally recognized that the main function of α-tocopherol (αToc), which is the most active form of vitamin E, is its antioxidant effect, while non-antioxidant effects have also been reported. We previously found that αToc ameliorates diabetic nephropathy via diacylglycerol kinase alpha (DGKα) activation in vivo, and the activation was not related to the antioxidant effect. However, the underlying mechanism of how αToc activates DGKα have been enigmatic. We report that the membrane-bound 67 kDa laminin receptor (67LR), which has previously been shown to serve as a receptor for epigallocatechin gallate (EGCG), also contains a novel binding site for vitamin E, and its association with Vitamin E mediates DGKα activation by αToc. We employed hydrogen-deuterium exchange mass spectrometry (HDX/MS) and molecular dynamics (MD) simulations to identify the specific binding site of αToc on the 67LR and discovered the conformation of the specific hydrophobic pocket that accommodates αToc. Also, HDX/MS and MD simulations demonstrated the detailed binding of EGCG to a water-exposed hydrophilic site on 67LR, while in contrast αToc binds to a distinct hydrophobic site. We demonstrated that 67LR triggers an important signaling pathway mediating non-antioxidant effects of αToc, such as DGKα activation. This is the first evidence demonstrating a membrane receptor for αToc and one of the underlying mechanisms of a non-antioxidant function for αToc.
普遍认为，α-生育酚（αToc）作为维生素 E 最活跃的形式，其主要功能是抗氧化作用，尽管也有报道称其具有非抗氧化作用。我们之前发现，αToc 通过体内二酰基甘油激酶α（DGKα）的激活来改善糖尿病肾病，而这种激活与抗氧化作用无关。然而，αToc 如何激活 DGKα 的潜在机制仍不清楚。我们报告称，先前已被证明作为表没食子儿茶素没食子酸酯（EGCG）受体的膜结合 67 kDa 层粘连蛋白受体（67LR），也包含维生素 E 的新结合位点，并且其与维生素 E 的关联介导了 αToc 对 DGKα 的激活。我们采用氘氚交换质谱（HDX/MS）和分子动力学（MD）模拟来确定 αToc 在 67LR 上的特定结合位点，并发现了容纳 αToc 的特定疏水性口袋的构象。此外，HDX/MS 和 MD 模拟表明 EGCG 与 67LR 上暴露于水的亲水位点的详细结合，而 αToc 则结合到不同的疏水性位点。我们证明了 67LR 触发介导 αToc 的非抗氧化作用的重要信号通路，如 DGKα 的激活。这是证明 αToc 的膜受体的第一个证据，也是 αToc 的非抗氧化作用的潜在机制之一。
