Gonzalez Jennifer, Du Mei, Parameshwaran Kodeeswaran, Suppiramaniam Vishnu, Jayaraman Vasanthi
Center for Membrane Biology, Department of Biochemistry and Molecular Biology, Graduate School of Biomedical Sciences, University of Texas Health Science Center, Houston, TX 77030, USA.
Proc Natl Acad Sci U S A. 2010 May 25;107(21):9891-6. doi: 10.1073/pnas.0911854107. Epub 2010 May 10.
The conversion of chemical to electrical signals by the AMPA receptors is the key step by which these proteins control cognitive and motor responses. Here, we have used luminescence resonance energy transfer (LRET) to gain insight into the conformational changes induced by glutamate binding in the agonist-binding domain in functional AMPA receptors expressed in oocytes and HEK-293 cells. The LRET-based distances indicate that the interface between the upper lobes of the agonist-binding domain within a dimer is in a decoupled state in the unligated Apo state of the receptor. Agonist binding results in the formation of the dimer interface in the open-channel form of the receptor. In the continued presence of glutamate when the receptor is primarily in the desensitized state, the dimer interface is decoupled, confirming that the decoupling of the dimer interface leads to channel closure. The LRET distances also indicate that the dimer interface is preformed before activation in the L484Y mutation and also is formed in the antagonist (ZK200775)-bound form of the AMPA receptor. These results suggests that, although the preformation of the interface is not sufficient to drive channel activation, it could play a role in the energetics of activation and hence modulation of the receptor by auxiliary proteins or small molecules.
AMPA 受体将化学信号转换为电信号是这些蛋白质控制认知和运动反应的关键步骤。在此，我们利用发光共振能量转移（LRET）来深入了解在卵母细胞和 HEK-293 细胞中表达的功能性 AMPA 受体的激动剂结合域中，谷氨酸结合所诱导的构象变化。基于 LRET 的距离表明，在受体的未结合配体的 Apo 状态下，二聚体内激动剂结合域上叶之间的界面处于解偶联状态。激动剂结合导致受体以开放通道形式形成二聚体界面。当受体主要处于脱敏状态且谷氨酸持续存在时，二聚体界面解偶联，证实二聚体界面的解偶联导致通道关闭。LRET 距离还表明，在 L484Y 突变体中，二聚体界面在激活前已预先形成，并且在与拮抗剂（ZK200775）结合的 AMPA 受体形式中也会形成。这些结果表明，虽然界面的预先形成不足以驱动通道激活，但它可能在激活的能量学中发挥作用，从而影响辅助蛋白或小分子对受体的调节。
