Evidence for the Quercetin Binding Site of Glycogen Phosphorylase as a Target for Liver-Isoform-Selective Inhibitors against Glioblastoma: Investigation of Flavanols Epigallocatechin Gallate and Epigallocatechin
Serafeim Alexopoulos, Megan McGawley, Roshini Mathews, Souzana Papakostopoulou, Symeon Koulas, Demetres D. Leonidas, Tamara Zwain, Joseph M. Hayes, Vasiliki Skamnaki
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引用次数: 0
Abstract
Glycogen phosphorylase (GP) is the rate-determining enzyme in glycogenolysis, and its druggability has been extensively studied over the years for the development of therapeutics against type 2 diabetes (T2D) and, more recently, cancer. However, the conservation of binding sites between the liver and muscle isoforms makes the inhibitor selectivity challenging. Using a combination of kinetic, crystallographic, modeling, and cellular studies, we have probed the binding of dietary flavonoids epigallocatechin gallate (EGCG) and epigallocatechin (EGC) to GP isoforms. The structures of rmGPb-EGCG and rmGPb-EGC complexes were determined by X-ray crystallography, showing binding at the quercetin binding site (QBS) in agreement with kinetic studies that revealed both compounds as noncompetitive inhibitors of GP, with EGCG also causing a significant reduction in cell viability and migration of U87-MG glioblastoma cells. Interestingly, EGCG exhibits different binding modes to GP isoforms, revealing QBS as a promising site for GP targeting, offering new opportunities for the design of liver-selective GP inhibitors.
糖原磷酸化酶(GP)是糖原分解过程中的速率决定酶,多年来,人们一直在广泛研究它的可药性,以开发针对 2 型糖尿病(T2D)和癌症的疗法。然而,由于肝脏和肌肉同工酶之间的结合位点保持不变,因此抑制剂的选择性具有挑战性。我们采用动力学、晶体学、建模和细胞研究相结合的方法,探究了膳食类黄酮表没食子儿茶素没食子酸酯(EGCG)和表没食子儿茶素(EGC)与 GP 同工酶的结合。X射线晶体学测定了rmGPb-EGCG和rmGPb-EGC复合物的结构,结果表明它们在槲皮素结合位点(QBS)结合,这与动力学研究一致,动力学研究显示这两种化合物都是GP的非竞争性抑制剂,EGCG还能显著降低U87-MG胶质母细胞瘤细胞的活力和迁移。有趣的是,EGCG 表现出与 GP 异构体不同的结合模式,揭示了 QBS 是 GP 靶向的一个有希望的位点,为设计肝脏选择性 GP 抑制剂提供了新的机遇。
期刊介绍:
The Journal of Agricultural and Food Chemistry publishes high-quality, cutting edge original research representing complete studies and research advances dealing with the chemistry and biochemistry of agriculture and food. The Journal also encourages papers with chemistry and/or biochemistry as a major component combined with biological/sensory/nutritional/toxicological evaluation related to agriculture and/or food.