Amino acid neurotransmitter sensors for MRI

描述（由申请人提供）：使用具有分子特异性、无创且跨越整个大脑的新型测量方法，可以显著加快对正常脑功能和疾病中涉及的神经机制的分析。在这里，我们建议开发一个分子传感器平台，用于通过无创磁共振成像（MRI）成像两种最重要的氨基酸神经递质，谷氨酸和γ -氨基丁酸（GABA）。传感器将通过修饰与钆螯合基团的氨基酸结合蛋白家族而形成。由此产生的探针将使“神经化学成像”具有与行为相关的时间分辨率，在整个大脑区域或完整大脑的规模上。这种定性的新能力将使我们和其他人能够回答脊椎动物中枢神经系统中主要的兴奋性和抑制性神经递质如何参与脑生理学的多个方面的具体问题。我们的传感器设计是基于在所谓的维纳斯捕蝇草域（vfd）中引起的大型配体依赖结构变化。通过在战略性选择的氨基酸位置将含钆基团偶联到VFD，我们期望生成对自然结合到每个相应VFD的配体敏感的MRI造影剂。在Aim 1中，我们将使用该策略基于细菌质周结合蛋白YbeJ的vfd生成谷氨酸敏感的MRI造影剂。在该Aim的初步工作中，我们已经观察到由于谷氨酸与钆衍生的YbeJ变体结合而导致的大MRI变化，表明我们的方法的总体前景。在目标2中，我们将在大鼠大脑中应用我们的谷氨酸传感器，并使用它们来绘制代表性体感刺激期间谷氨酸释放模式。我们还将比较谷氨酸和传统的功能磁共振成像（fMRI）激活图，以检验血液动力学fMRI测量密切反映谷氨酸能信号的假设。我们最近在大鼠大脑中使用一种不太有效的MRI传感器检测多巴胺释放，这为提出的体内工作提供了先例，并再次表明了前景。在Aim 3中，我们将扩展我们的谷氨酸传感器设计策略，以GABA为目标，GABA是大脑中主要的抑制性神经递质。拟议中的研究

DESCRIPTION (provided by applicant): Analysis of neural mechanisms involved in normal brain function and disease could be dramatically accelerated using novel measurement methods that report neural processing events with molecular specificity, noninvasively, and across the entire brain. Here we propose to develop a molecular sensor platform for imaging the two most important amino acid neurotransmitters, glutamate and gamma-aminobutyric acid (GABA), by noninvasive magnetic resonance imaging (MRI). Sensors will be formed by modifying a family of amino acid binding proteins with gadolinium chelating groups. The resulting probes will enable "neurochemical imaging" with behaviorally-relevant temporal resolution, on the scale of entire brain regions or intact brains. This qualitatively new capabilit will enable us and others to answer specific questions about how the dominant excitatory and inhibitory neurotransmitters in the vertebrate central nervous system participate in multiple facets of brain physiology. Our sensor design is based on the large ligand-dependent structural changes induced in so-called venus flytrap domains (VFDs). By conjugating gadolinium-containing groups to VFDs at strategically chosen amino acid positions, we expect to generate MRI contrast agents with sensitivity to the ligands that naturally bind to each corresponding VFD. In Aim 1, we will use this strategy to generate glutamate-sensitive MRI contrast agents based on VFDs from the bacterial periplasmic binding protein YbeJ. In preliminary work on this Aim, we have already observed large MRI changes due to glutamate binding to gadolinium-derivatized YbeJ variants, indicating the overall promise of our approach. In Aim 2, we will apply our glutamate sensors in rat brains and use them to map glutamate release patterns during a representative somatosensory stimulus. We will also compare glutamate and conventional functional MRI (fMRI) activation maps to examine the hypothesis that hemodynamic fMRI measures closely reflect glutamatergic signaling. Our recent detection of dopamine release using a less potent form of MRI sensor in rat brains represents a precedent for the proposed in vivo work, and again indicates promise. In Aim 3, we will extend our glutamate sensor design strategy to target GABA, the dominant inhibitory neurotransmitter in the brain. The proposed research has