Department of Biological Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
Department of Biochemistry, The University of Oxford, Oxford, UK.
Nat Commun. 2022 Aug 11;13(1):4714. doi: 10.1038/s41467-022-32442-6.
Glutamate is a pivotal excitatory neurotransmitter in mammalian brains, but excessive glutamate causes numerous neural disorders. Almost all extracellular glutamate is retrieved by the glial transporter, Excitatory Amino Acid Transporter 2 (EAAT2), belonging to the SLC1A family. However, in some cancers, EAAT2 expression is enhanced and causes resistance to therapies by metabolic disturbance. Despite its crucial roles, the detailed structural information about EAAT2 has not been available. Here, we report cryo-EM structures of human EAAT2 in substrate-free and selective inhibitor WAY213613-bound states at 3.2 Å and 2.8 Å, respectively. EAAT2 forms a trimer, with each protomer consisting of transport and scaffold domains. Along with a glutamate-binding site, the transport domain possesses a cavity that could be disrupted during the transport cycle. WAY213613 occupies both the glutamate-binding site and cavity of EAAT2 to interfere with its alternating access, where the sensitivity is defined by the inner environment of the cavity. We provide the characterization of the molecular features of EAAT2 and its selective inhibition mechanism that may facilitate structure-based drug design for EAAT2.
谷氨酸是哺乳动物大脑中至关重要的兴奋性神经递质，但过量的谷氨酸会导致多种神经紊乱。几乎所有细胞外的谷氨酸都是由神经胶质转运体谷氨酸转运蛋白 2（EAAT2）回收的，EAAT2 属于 SLC1A 家族。然而，在某些癌症中，EAAT2 的表达增强，通过代谢紊乱导致对治疗产生耐药性。尽管其作用至关重要，但 EAAT2 的详细结构信息尚不清楚。在这里，我们报道了在无底物和选择性抑制剂 WAY213613 结合状态下，人源 EAAT2 的冷冻电镜结构，分辨率分别为 3.2Å 和 2.8Å。EAAT2 形成三聚体，每个单体由转运和支架结构域组成。转运结构域除了谷氨酸结合位点外，还具有一个可能在转运循环过程中被破坏的空腔。WAY213613 占据 EAAT2 的谷氨酸结合位点和空腔，干扰其交替进入，其敏感性由空腔的内部环境决定。我们提供了 EAAT2 的分子特征和其选择性抑制机制的表征，这可能有助于基于结构的 EAAT2 药物设计。
