Recovery from AMPA Receptor Desensitization

描述(申请人提供)：AMPA亚型的离子型谷氨酸受体(GluRs)介导哺乳动物中枢神经系统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。这些通道的一个显著特征是，它们在几毫秒内脱敏，在一些中枢神经系统突触，脱敏有助于塑造EPSCs的衰退。由于谷氨酸浓度在低微摩尔范围内可以产生几乎完全的脱敏，大多数突触脱敏可能发生在单个EPSCs中，甚至在环境中谷氨酸水平下可能显著。因此，通道从脱敏中恢复的速度是中枢神经系统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，我们提出了一系列生物物理实验，旨在回答关于控制AMPA受体脱敏恢复的动力学和结构特征的三个问题。 1)再敏化和配体解离对恢复动力学的相对贡献是什么？对于不同的激动剂它们是否有所不同？ 2)在脱敏过程中，配体结合域关闭的程度如何？对于单个亚基，这一点是否有所不同？ 3)经济复苏速度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?