Molecular Mechanisms of Semaphorin/Plexin-mediated Cytoskeletal Reorganization

信号蛋白/丛蛋白介导的细胞骨架重组的分子机制

• 批准号: 8423045
• 负责人: JONATHAN R TERMAN
• 金额: $ 33.56万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-02-15 至 2016-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8423045
• 关键词: Actins; Addictive Behavior; Adult; Behavior; Binding; Biochemical; Biochemistry; Biological; Biological Assay; Biological Models; Cell Culture Techniques; Cell Surface Receptors; Cell surface; Cells; Cellular biology; Cues; Cultured Cells; Cytoskeletal Modeling; Cytoskeleton; Dendrites; Development; Diagnosis; Drosophila genus; Emotions; Enzymes; Event; F-Actin; Family; Filament; Functional disorder; Genes; Genetic; Goals; Image; In Vitro; Injury; Invertebrates; Learning; Length; Link; Logic; Mammals; Mass Spectrum Analysis; Mediating; Microfilaments; Modification; Molecular; Morphology; Movement; Mutagenesis; NADP; Nervous system structure; Neurons; Neurosciences Research; Oxidation-Reduction; Oxidoreductase; Post-Translational Protein Processing; Prevention strategy; Process; Property; Proteins; Publishing; Recovery; Regulation; Resolution; Role; Semaphorins; Shapes; Signal Pathway; Signal Transduction; Specific qualifier value; Structure; Synaptic Transmission; Testing; Therapeutic; Time; Total Internal Reflection Fluorescent; Trauma; Vertebral column; Walking; adhesion process; axon growth; axon guidance; base; cell behavior; cell motility; depolymerization; direct application; extracellular; in vivo; member; migration; nervous system disorder; novel; plexin; polymerization; prevent; public health relevance; receptor; relating to nervous system; response; structural biology; synaptogenesis

DESCRIPTION (provided by applicant): The goals of this project are to characterize a new biological mechanism that has direct application to the regulation of the actin cytoskeleton - the structure underlying neural cell behaviors including morphology, polarity, adhesion, process elongation, motility, navigation, connectivity, and plasticity. In order to change their size, shape, and connectivity, neurons require actin proteins to assemble together into long filaments. Adjusting the length and organization of these actin filaments (F-actin) specifies the direction of movement and enables cells to precisely connect and communicate with one another. A number of extracellular cues have now been identified that control actin dynamics, but we know little of how these signals present outside of cells exert their precise effects within cells. Semaphorins (Semas) are one of the largest families of these guidance cues and they regulate cellular behaviors by eliciting destabilizing effects on F-actin that include a loss of F- actin and the decreased ability to polymerize new F-actin. Importantly, recent breakthroughs have identified cell-surface receptors and intracellular proteins that are essential for Sema-mediated effects on actin but we still know little of the molecular mechanisms that directly regulate F-actin in response to Semas. To identify these molecules and mechanisms we have identified proteins that associate with the Sema receptor Plexin, including a novel family of cytosolic proteins called the MICALs. There is one MICAL gene in invertebrates and three MICAL genes in mammals and they control axon guidance, synaptogenesis, dendritic pruning, and other morphological changes mediated Semas/Plexins. Indeed, our recently published results reveal that MICAL provides a long-sought-after direct link between Semas/Plexins and the modification of the actin cytoskeleton. We find that MICAL directly disassembles F-actin and is both necessary and sufficient for regulating actin dynamics downstream of Semas/Plexins. These new results provide an underlying logic through which Sema- mediated reorganizations of the actin cytoskeleton can be precisely achieved in space and time: through direct Sema-Plexin activation of the novel actin disassembly factor MICAL. Interestingly, MICALs also contain an oxidoreductase (Redox) enzymatic moiety and our results strongly suggest that MICAL utilizes its Redox activity to alter F-actin, implicating for the first time a role for specific Redox signaling events in actin cytoskeletal regulation. Therefore, I hypothesize that MICAL enzymes are a novel family of phylogenetically conserved actin disassembly factors that utilize a previously uncharacterized reversible Redox signaling mechanism to directly regulate actin dynamics. To test this hypothesis, I propose to combine genetics, cell culture, and cell biological approaches using both invertebrate and vertebrate model systems with biochemical, structural, and high-resolution imaging assays utilizing purified MICAL and actin proteins. Understanding how this unusual family of enzymes, the MICALs (which are unlike any proteins that have ever been characterized) causes F-actin to disassemble will reveal new strategies to regulate neural cell biology and behavior.

描述（由申请人提供）：本项目的目标是描述一种新的生物学机制，该机制直接应用于肌动蛋白细胞骨架的调节-神经细胞行为的基础结构，包括形态，极性，粘附，过程延伸，运动，导航，连接和可塑性。为了改变它们的大小、形状和连接性，神经元需要肌动蛋白组装成长长的细丝。调整这些肌动蛋白丝（F-actin）的长度和组织指定了运动方向，使细胞能够精确地相互连接和交流。现在已经确定了许多控制肌动蛋白动力学的细胞外信号，但我们对这些存在于细胞外的信号如何在细胞内发挥其精确作用知之甚少。脑信号蛋白（Semaphorins，Semas）是这些引导信号中最大的家族之一，它们通过引起对F-肌动蛋白的去稳定作用来调节细胞行为，所述去稳定作用包括F-肌动蛋白的损失和新的F-肌动蛋白合成能力的降低。重要的是，最近的突破已经确定了细胞表面受体和细胞内蛋白质是必不可少的Sema介导的肌动蛋白的影响，但我们仍然知道很少的分子机制，直接调节F-肌动蛋白响应Sema。为了鉴定这些分子和机制，我们鉴定了与Sema受体丛状蛋白相关的蛋白质，包括一种称为MICAL的新型胞质蛋白家族。在无脊椎动物中有一个MICAL基因，在哺乳动物中有三个MICAL基因，它们控制轴突导向、突触发生、树突修剪和其他介导Semas/Plexins的形态学变化。事实上，我们最近发表的结果表明，MICAL提供了一个长期寻求的Sema/丛蛋白和肌动蛋白细胞骨架的修饰之间的直接联系。我们发现，MICAL直接拆卸F-肌动蛋白，是必要的和足够的调节肌动蛋白动态下游的Sema/丛蛋白。这些新的结果提供了一个潜在的逻辑，通过该逻辑，可以在空间和时间上精确地实现Sema介导的肌动蛋白细胞骨架的重组：通过直接激活新型肌动蛋白分解因子MICAL。有趣的是，MICAL还含有氧化还原酶（Redox）的酶部分，我们的研究结果强烈表明，MICAL利用其氧化还原活性改变F-肌动蛋白，首次暗示了特定的氧化还原信号事件在肌动蛋白细胞骨架调节中的作用。因此，我假设MICAL酶是一个新的家族，利用以前未表征的可逆氧化还原信号传导机制，直接调节肌动蛋白动力学的遗传保守的肌动蛋白分解因子。为了验证这一假设，我建议结合联合收割机遗传学，细胞培养和细胞生物学的方法，使用无脊椎动物和脊椎动物的模型系统与生化，结构和高分辨率的成像分析，利用纯化的MICAL和肌动蛋白。了解这种不寻常的酶家族，MICAL（与任何已被表征的蛋白质不同）如何导致F-肌动蛋白分解将揭示调节神经细胞生物学和行为的新策略。