Recovery from AMPA Receptor Desensitization

描述（由申请人提供）：离子型谷氨酸受体（GluR）的AMPA亚型介导哺乳动物CNS中绝大多数兴奋性突触传递，并参与突触强度的各种可塑性变化。这些通道的一个标志性特征是它们在几毫秒内脱敏，并且在某些CNS突触处脱敏有助于形成EPSC的衰变。由于低微摩尔浓度的谷氨酸盐可以产生几乎完全的脱敏，因此大多数突触脱敏可能发生在单个EPSC期间，并且甚至可能在谷氨酸盐的环境水平下显著。因此，通道从脱敏中恢复的速率是CNS神经元能够跟随高频突触前放电的保真度的关键决定因素。在这里，我们提出了一系列的生物物理实验，旨在回答三个问题的动力学和结构特征，控制AMPA受体脱敏恢复。 1)再致敏和配体解离对恢复动力学的相对贡献是什么？它们对不同的激动剂有何不同？ 2)在脱敏过程中，配体结合结构域关闭到什么程度？这对个体亚基有何不同？ 3)复苏率的结构性决定因素是什么？

DESCRIPTION (provided by applicant): The AMPA subtype of ionotropic glutamate receptors (GluRs) mediate the vast majority of excitatory synaptic transmission in the mammalian CNS and participate in a variety of plastic changes in synaptic strength. One hallmark feature of these channels is that they desensitize in a few milliseconds, and at some CNS synapses desensitization contributes to shaping the decay of EPSCs. Because concentrations of glutamate in the low micromolar range can produce nearly complete desensitization, at most synapses desensitization likely occurs during single EPSCs and may even be significant at ambient levels of glutamate. Thus the rate at which channels recover from desensitization is a key determinant of the fidelity with which CNS neurons are able to follow high-frequency presynaptic firing. Here we propose a series of biophysical experiments designed to answer three questions about the kinetic and structural features that control recovery from AMPA-receptor desensitization. 1) What are the relative contributions of re-sensitization and ligand dissociation to the kinetics of recover and do they vary for different agonists? 2) To what extent is the ligand binding domain closed during desensitization and does this vary for individual subunits? 3) What are the structural determinants of the rate of recovery?