AMPA glutamate receptors (AMPARs) mediate excitatory neurotransmission throughout the brain. Their signalling is uniquely diversified by brain region-specific auxiliary subunits, providing an opportunity for the development of selective therapeutics. AMPARs associated with TARP γ8 are enriched in the hippocampus, and are targets of emerging anti-epileptic drugs. To understand their therapeutic activity, we determined cryo-EM structures of the GluA1/2-γ8 receptor associated with three potent, chemically diverse ligands. We find that despite sharing a lipid-exposed and water-accessible binding pocket, drug action is differentially affected by binding-site mutants. Together with patch-clamp recordings and MD simulations we also demonstrate that ligand-triggered reorganisation of the AMPAR-TARP interface contributes to modulation. Unexpectedly, one ligand (JNJ-61432059) acts bifunctionally, negatively affecting GluA1 but exerting positive modulatory action on GluA2-containing AMPARs, in a TARP stoichiometry-dependent manner. These results further illuminate the action of TARPs, demonstrate the sensitive balance between positive and negative modulatory action, and provide a mechanistic platform for development of both positive and negative selective AMPAR modulators.

AMPA 谷氨酸受体 (AMPAR) 介导整个大脑的兴奋性神经传递。它们的信号传导通过大脑区域特异性辅助亚基而独特地多样化，为选择性疗法的开发提供了机会。与 TARP γ8 相关的 AMPAR 在海马中富集，是新兴抗癫痫药物的靶标。为了了解它们的治疗活性，我们确定了与三种有效的化学多样性配体相关的 GluA1/2-γ8 受体的冷冻电镜结构。我们发现，尽管共享脂质暴露和水可及的结合袋，但药物作用受到结合位点突变体的不同影响。结合膜片钳记录和 MD 模拟，我们还证明配体触发的 AMPAR-TARP 界面重组有助于调节。出乎意料的是，一种配体 (JNJ-61432059) 具有双功能，对 GluA1 产生负面影响，但以 TARP 化学计量依赖性方式对含有 GluA2 的 AMPAR 发挥正向调节作用。这些结果进一步阐明了 TARP 的作用，证明了正负调节作用之间的敏感平衡，并为开发正负选择性 AMPAR 调节剂提供了机制平台。