Signaling Mechanisms Regulating Rac-dependent Synaptic and Dendritic Development

调节 Rac 依赖性突触和树突发育的信号机制

• 批准号: 10191751
• 负责人: Kimberly R Tolias
• 金额: $ 40万
• 依托单位: BAYLOR COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2022-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10191751
• 关键词: Actins; Alzheimer' s Disease; Behavior; Behavioral; Binding; Biochemical; Biochemistry; Biological Assay; Bipolar Disorder; Brain; Brain Diseases; Cells; Cognition; Cognition Disorders; Cognitive; Complex; Couples; Coupling; Data; Dendritic Spines; Development; Disease; Down Syndrome; Electrophysiology (science); Excitatory Synapse; Exhibits; Fluorescence Resonance Energy Transfer; Fright; Functional disorder; GTPase-Activating Proteins; Gene Expression; Glutamate Receptor; Grant; Growth; Guanine Nucleotide Exchange Factors; Hippocampus (Brain); Human; Intellectual functioning disability; Knockout Mice; Knowledge; Learning; Link; Maintenance; Major Depressive Disorder; Measures; Mediating; Membrane; Memory; Mental Depression; Modeling; Molds; Molecular and Cellular Biology; Monitor; Mood Disorders; Moods; N-Methylaspartate; Nature; Neurons; Neurosciences; PHluorin; Pathology; Pathway interactions; Patients; Pattern; Play; Positioning Attribute; Process; Publishing; Regulation; Resolution; Role; Shapes; Signal Transduction; Signal Transduction Pathway; Specificity; Surface; Synapses; Synaptic Receptors; Synaptic Transmission; Synaptic plasticity; Techniques; Testing; Time; Vertebral column; Work; autism spectrum disorder; base; behavior test; confocal imaging; depressive symptoms; in vivo; in vivo two-photon imaging; information processing; insight; interdisciplinary approach; mood regulation; mouse genetics; neural circuit; new therapeutic target; protein complex; response; rho GTP-Binding Proteins; rhoA GTP-Binding Protein; spatiotemporal; synaptogenesis; time use; trafficking

PROJECT SUMMARY Neural circuit formation and information processing in the brain require precise control of the development and remodeling of actin-rich dendritic spines and the excitatory synapses they house. Dynamic regulation of AMPA- and NMDA-type glutamate receptors, which mediate fast excitatory synaptic transmission and synaptic plasticity, respectively, is a key aspect of this control. Synaptic pathology characterizes many brain disorders including intellectual disabilities, autism, bipolar disorder, depression, and Alzheimer's disease. Thus, uncovering the mechanisms that control spine/synapse development and glutamate receptor regulation will provide critical insights into brain function and disease. Rho GTPases are master regulators of spine/synapse development and remodeling. Rac1 promotes spine/synapse formation, growth and maintenance, whereas RhoA suppresses these processes; both also play pivotal roles in synaptic plasticity. Proper function of Rho GTPases requires exquisite spatiotemporal control and disruption of this regulation results in numerous brain disorders. Rho GTPases are activated by guanine nucleotide exchange factors (GEFs) and inhibited by GTPase activating proteins (GAPs). However, remarkably little is known about how these GEFs/GAPs shape spatiotemporal Rac1/RhoA activation patterns and effector responses that direct the formation of neural circuits in brain. We identified the Rac1-GEF Tiam1 as a critical regulator of dendrite, spine, and synapse de- velopment, demonstrating that it couples synaptic receptors to Rac1 activation and actin cytoskeletal remodeling in cultured hippocampal neurons. In the last grant cycle, we made the surprising discovery that Tiam1 binds to the Rac1-GAP/RhoA-GEF Bcr and that this GEF/GAP complex is required to precisely regulate synaptic Rac1 signaling and excitatory synapse formation. Bcr is linked to bipolar disorder and learning and behavioral deficits, whereas altered Tiam1 expression is seen in patients with depression and Down syndrome. We hypothesize that Tiam1/Bcr cooperate to control the activation dynamics and signaling specificity of Rho GTPases, which is required in vivo for proper spine/synapse development, NMDAR trafficking/function, learning, and mood regulation. To test this, we propose to: (1) identify the roles of Tiam1 and closely related Tiam2 in shaping spine/synapse development in vivo and the specific pathways that mediate their effects; and (2) elucidate the mechanisms by which Tiam1/Bcr control NMDARs in synaptic plasticity, learning and mood regulation. We will use a multidisciplinary approach involving mouse genetics, time-lapse live-cell and in vivo two-photon imaging, Förster Resonance Energy Transfer (FRET), electrophysiology, biochemistry, molecular and cellular biology, and behavioral analyses. Our findings will elucidate key mechanisms that control Rho GTPase-dependent synaptic development/plasticity, providing critical insight into normal brain development, the connection between altered Rho GTPase signaling and cognitive/mood disorders, and potential treatments.

项目摘要 大脑中的神经回路形成和信息处理需要精确控制神经回路的发育， 肌动蛋白丰富的树突棘和兴奋性突触的重塑。动态调节 AMPA型和NMDA型谷氨酸受体，介导快速兴奋性突触传递和突触传递。 塑性分别是这种控制的关键方面。突触病理学是许多脑部疾病的特征 包括智力障碍、自闭症、躁郁症、抑郁症和阿尔茨海默病。因此，在本发明中， 揭示控制脊柱/突触发育和谷氨酸受体调节的机制将 对大脑功能和疾病提供了重要的见解。Rho GTP酶是脊柱/突触的主要调节因子 发展和重塑。Rac 1促进棘/突触的形成、生长和维持，而 RhoA抑制这些过程;两者在突触可塑性中也起着关键作用。Rho的本征函数 GTP酶需要精确的时空控制，这种调节的中断导致许多脑损伤。 紊乱Rho GTP酶被鸟嘌呤核苷酸交换因子（GEF）激活，并被 GTP酶激活蛋白（GAP）。然而，对于这些GEF/GAP如何形成， 时空Rac 1/RhoA激活模式和效应器反应，指导神经元的形成 大脑中的回路我们确定Rac 1-GEF Tiam 1是树突、棘和突触脱髓鞘的关键调节因子， 结果表明，它将突触受体与Rac 1激活和肌动蛋白细胞骨架结合， 培养的海马神经元重塑。在上一个资助周期，我们有了一个惊人的发现， Tiam 1与Rac 1-GAP/RhoA-GEF Bcr结合，并且需要这种GEF/GAP复合物来精确调节 突触Rac 1信号传导和兴奋性突触形成。Bcr与双相情感障碍和学习有关， 行为缺陷，而Tiam 1表达改变见于抑郁症和唐氏综合征患者。 我们假设Tiam 1/Bcr协同控制Rho的激活动力学和信号特异性 GTP酶，其在体内对于适当的脊柱/突触发育、NMDAR运输/功能是必需的， 学习和情绪调节。为了验证这一点，我们建议：（1）确定Tiam 1的作用和密切相关的 Tiam 2在体内形成脊柱/突触发育中的作用以及介导其作用的特定途径;以及 (2)阐明Tiam 1/Bcr在突触可塑性、学习和情绪中控制NMDAR的机制 调控我们将使用多学科的方法，涉及小鼠遗传学，延时活细胞和体内 双光子成像，福斯特共振能量转移（FRET），电生理学，生物化学，分子生物学 细胞生物学和行为分析。我们的发现将阐明控制Rho的关键机制 GTP酶依赖性突触发育/可塑性，提供对正常大脑发育的重要见解， 改变的Rho GT3信号传导和认知/情绪障碍之间的联系，以及潜在的治疗方法。