Allosteric control of NMDA receptors

描述(申请人提供)：NMDA受体(NRs)在大脑中介导快速兴奋性传递。它们的激活对兴奋性突触的正常发育、维持和持续重构至关重要。NR活性过高是中风、慢性疼痛、癫痫和神经退行性疾病的发病机制，而NR信号不足与精神分裂症和认知障碍有关。许多内源性和药理学药物调节NR的活性，是治疗干预的潜在候选者。关于变构控制NR活性的机制还不是很清楚，控制NR功能的经验尝试到目前为止都没有得到令人失望的结果。其目的是从分子机制、整合以及对突触生理的影响等方面了解变构调节剂如何调控NR的生理功能。本研究的目的是：i)研究不同的NR变构调节剂对NR门控动力学和非平稳宏观行为的影响；ii)确定多种变构信号如何整合以产生具有不同信号特征的反应；iii)研究NR反应的变构调节对突触生理的影响。首先，利用单通道电流的动力学分析和统计建模，我们将识别和量化各个调节器在门控过程中对NR基本动力学转变的作用。这些测量的速率常数本质上蕴含着丰富的机制信息；此外，它们还可以预测调节剂对NR宏观行为和NR介导的突触功能的影响。这些预测将通过测量在切除的膜片中对模式刺激的整体NR反应和通过测量脑片中诱发的NR突触反应来验证。对于激活反应复杂的NRs来说，这种方法是全新的，可能会找到有效的手段来调节相互分离的特定受体功能。综上所述，这些结果将有助于汇编一个关于变构控制NR活性如何影响突触生理的综合机制观点。这一观点应该提出新的组合方法，以特别针对有害的受体行为，同时保留NRs所发挥的关键功能。

DESCRIPTION (provided by applicant): NMDA receptors (NRs) mediate fast excitatory transmission in the brain. Their activation is critical for the normal development, maintenance and continual remodeling of excitatory synapses. Excessive NR activity is a disease mechanism in stroke, chronic pain, epilepsy, and neurodegenerative disease, whereas insufficient NR signaling has been involved with schizophrenia and cognitive disorders. Numerous endogenous and pharmacologic agents modulate NR activities and are potential candidates for therapeutic intervention. The mechanisms governing the allosteric control of NR activity are poorly understood and empirical attempts to control NR function have so far yielded disappointing results. The OBJECTIVE is to understand how allosteric modulators control NR physiologic functions in terms of molecular mechanisms, integration and consequences on synaptic physiology. The AIMS addressed in this proposal are to: i) characterize individual NR allosteric modulators in terms of their effects on NR gating dynamics and on non-stationary macroscopic behaviors; ii) establish how multiple allosteric signals are integrated to result in responses with distinct signaling profiles; and iii) investigate how allosteric modulation of NR responses impacts on synaptic physiology. First, using kinetic analysis of single-channel currents and statistical modeling we will identify and quantify the actions of individual modulators on NR elementary kinetic transitions during gating. These measured rate constants are intrinsically rich with mechanistic information; in addition they can predict modulator effects on NR macroscopic behaviors and on NR- mediated synaptic function. These predictions will be verified by measuring ensemble NR responses to patterned stimulation in excised membrane patches and by measuring evoked NR synaptic responses in brain slices. For NRs whose activation reaction is complex, this approach is entirely novel and may identify effective means to modulate specific receptor functions in separation of each other. Taken together the results will help to compile an integrated mechanistic view of how allosteric control of NR activity impacts synaptic physiology. This view should suggest new, combinatorial approaches to specifically target harmful receptor behaviors while preserving the critical functions played by NRs .