钙离子(Ca2+)通过几种不同的机制降低NMDA受体电流。其中,钙调蛋白(CaM)依赖性抑制(CDI)实现快速,可逆,以及响应细胞内Ca2升高的NMDA受体电流的不完全降低。NMDA受体介导的信号的CDI的定量和机制描述已被变异性起源所破坏,在某种程度上,来自实验室中用于评估此过程的条件和指标的差异。最近测量NMDA受体CDI的大小和动力学的比率方法促进了对该现象的快速了解。值得注意的是,NMDA受体CDI的动力学和大小取决于其CaM结合位点的饱和度,它们代表了这种抑制作用的真正的钙传感器,Ca2+信号的动力学和大小,这取决于NMDA受体或相邻Ca2来源的生物物理特性,以及Ca2+源和CaM分子的相对分布。鉴于所有这些因素在开发过程中差异很大,跨细胞类型,以及生理和病理状态,重要的是要了解NMDA受体CDI如何发展以及它如何促进中枢神经系统的信号传导。这里,我们简要回顾了这些最新进展,并强调了关于NMDA受体CDI的结构和动力学机制的剩余问题。鉴于病理可能来自多个来源,包括NMDA受体和CaM的突变,了解CaM如何响应细胞内Ca2信号以启动NMDA受体的构象变化,绘制负责的结构域将有助于设想神经精神疾病的新治疗策略,目前可用的治疗方法有限。
Calcium ions (Ca2+) reduce NMDA receptor currents through several distinct mechanisms. Among these, calmodulin (CaM)-dependent inhibition (CDI) accomplishes rapid, reversible, and incomplete reduction of the NMDA receptor currents in response to elevations in intracellular Ca2+. Quantitative and mechanistic descriptions of CDI of NMDA receptor-mediated signals have been marred by variability originating, in part, from differences in the conditions and metrics used to evaluate this process across laboratories. Recent ratiometric approaches to measure the magnitude and kinetics of NMDA receptor CDI have facilitated rapid insights into this phenomenon. Notably, the kinetics and magnitude of NMDA receptor CDI depend on the degree of saturation of its CaM binding sites, which represent the bona fide calcium sensor for this type of inhibition, the kinetics and magnitude of the Ca2+ signal, which depends on the biophysical properties of the NMDA receptor or of adjacent Ca2+ sources, and on the relative distribution of Ca2+ sources and CaM molecules. Given that all these factors vary widely during development, across cell types, and with physiological and pathological states, it is important to understand how NMDA receptor CDI develops and how it contributes to signaling in the central nervous system. Here, we review briefly these recent advances and highlight remaining questions about the structural and kinetic mechanisms of NMDA receptor CDI. Given that pathologies can arise from several sources, including mutations in the NMDA receptor and in CaM, understanding how CaM responds to intracellular Ca2+ signals to initiate conformational changes in NMDA receptors, and mapping the structural domains responsible will help to envision novel therapeutic strategies to neuropsychiatric diseases, which presently have limited available treatments.