Institute of Biology, Cellular Biophysics, Humboldt Universität zu Berlin, Berlin, Germany.
Molecular Physiology and Cell Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany.
Elife. 2017 Aug 30;6:e28680. doi: 10.7554/eLife.28680.
At synapses throughout the mammalian brain, AMPA receptors form complexes with auxiliary proteins, including TARPs. However, how TARPs modulate AMPA receptor gating remains poorly understood. We built structural models of TARP-AMPA receptor complexes for TARPs γ2 and γ8, combining recent structural studies and de novo structure predictions. These models, combined with peptide binding assays, provide evidence for multiple interactions between GluA2 and variable extracellular loops of TARPs. Substitutions and deletions of these loops had surprisingly rich effects on the kinetics of glutamate-activated currents, without any effect on assembly. Critically, by altering the two interacting loops of γ2 and γ8, we could entirely remove all allosteric modulation of GluA2, without affecting formation of AMPA receptor-TARP complexes. Likewise, substitutions in the linker domains of GluA2 completely removed any effect of γ2 on receptor kinetics, indicating a dominant role for this previously overlooked site proximal to the AMPA receptor channel gate.
在哺乳动物大脑的各个突触中，AMPA 受体与辅助蛋白（包括 TARPs）形成复合物。然而，TARPs 如何调节 AMPA 受体门控仍知之甚少。我们为 TARPs γ2 和 γ8 构建了 TARP-AMPA 受体复合物的结构模型，结合了最近的结构研究和从头预测结构。这些模型结合肽结合测定，为 GluA2 与 TARPs 的可变细胞外环之间的多种相互作用提供了证据。这些环的取代和缺失对谷氨酸激活电流的动力学有惊人丰富的影响，而对组装没有任何影响。至关重要的是，通过改变 γ2 和 γ8 的两个相互作用环，我们可以完全消除 GluA2 的所有变构调节，而不影响 AMPA 受体-TARP 复合物的形成。同样，GluA2 连接域中的取代完全消除了 γ2 对受体动力学的任何影响，表明该先前被忽视的位于 AMPA 受体通道门附近的位点起主导作用。
