Positive Feedback Loops in Growth Cone Symmetry Breaking and Guidance Signaling

生长锥对称性破缺和引导信号传导中的正反馈环

• 批准号: 8499065
• 负责人: Thomas R Cheever
• 金额: $ 0.75万
• 依托单位: MAYO CLINIC ROCHESTER
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-06-20 至 2013-07-19
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8499065
• 关键词: 1-Phosphatidylinositol 3-Kinase; Actins; Adhesions; Adult; Axon; Biological Assay; Biological Models; Biosensor; Cell membrane; Cells; Chemotaxis; Cues; Cytoskeleton; Development; Developmental Process; Dictyostelium; Disease; Dominant-Negative Mutation; Embryonic Development; Ensure; Exhibits; Feedback; Fluorescence; Goals; Growth; Growth Cones; Image; Injury; Life; Lipids; Measures; Mediating; Membrane; Molecular; Natural regeneration; Nerve; Nerve Degeneration; Nerve Regeneration; Nervous system structure; Neurodegenerative Disorders; Neurons; Phosphatidylinositols; Phosphotransferases; Production; Proteins; Receptor Activation; Resistance; Role; Second Messenger Systems; Side; Signal Pathway; Signal Transduction; Signaling Molecule; Source; Spinal; Spinal cord injury; Stroke; Synapses; System; Testing; Therapeutic Intervention; Work; Xenopus; base; cell motility; cellular imaging; effective therapy; extracellular; functional restoration; innovation; insight; mutant; neural circuit; neuronal growth; neutrophil; new therapeutic target; novel; phosphatidylinositol 3,4,5-triphosphate; programs; response; rho GTP-Binding Proteins; second messenger

DESCRIPTION (provided by applicant): Restoring functional connections within the nervous system following injury or disease represents a significant challenge in the development of effective treatments for stroke, spinal cord injury, and neurodegenerative conditions. Because the adult nervous system is relatively resistant to the functional restoration of neural circuits, t is believed that recapitulating programs used during the initial formation of these circuits holds significant promise for encouraging nerve regeneration following injury or disease. During embryonic development, nerve growth is guided by minute gradients of extracellular guidance cues. How these guidance cue signals are locally amplified within growth cones at the tip of elongating nerves remains a critical question. Evidence from a number of model systems that exhibit chemotactic growth towards extracellular signals indicates that positive feedback loops are often used to locally amplify extracellular cues and generate the cellular asymmetry required for guided cell migration. The goal of this proposal is to ascertain whether similar mechanisms are at work in neuronal growth cones, and to define the components and function of these signaling pathways. Based on work by other groups and our own, WE HYPOTHESIZE that extracellular guidance cue signals are asymmetrically amplified within the growth cone by a positive feedback loop comprised of the lipid signaling molecule phosphatidylinositol (PI) 3,4,5-triphosphate (PIP3), the lipid kinase PI-3 kinase (PI3K), the Rho GTPase Rac, and actin dynamics. Furthermore, we propose that Ca2+ functions in a positive feedback loop with PIP3 in growth cones to promote the localized accumulation of PIP3 and Rac activity. In order to characterize these putative positive feedback loops in growth cones, we will use pharmacological and molecular approaches along with innovative biosensors in live neuronal cultures to identify the components and function of a PIP3-PI3K-Rac-actin dynamics positive feedback loop (aim 1), as well as the contribution of cytoplasmic Ca2+ signaling to the amplification of asymmetric PIP3 signals and growth cone turning (aim 2). Collectively, the work described in this proposal will provide novel insight into how local guidance cue signals are amplified and contribute to the growth cone symmetry breaking required for turning and outgrowth to proper synaptic targets.

描述（由申请人提供）：在损伤或疾病后恢复神经系统内的功能连接是开发中风、脊髓损伤和神经退行性疾病的有效治疗方法的重大挑战。由于成人神经系统对神经回路的功能恢复相对有抵抗力，因此人们相信，在这些回路最初形成期间使用的重演程序对于鼓励损伤或疾病后的神经再生具有重要的前景。在胚胎发育过程中，神经生长受到细胞外引导信号的微小梯度的引导。这些引导信号如何在伸长神经尖端的生长锥内局部放大仍然是一个关键问题。来自许多对细胞外信号表现出趋化生长的模型系统的证据表明，正反馈回路通常用于局部放大细胞外信号并产生引导细胞迁移所需的细胞不对称性。该提案的目的是确定类似的机制是否在神经元生长锥中起作用，并定义这些信号通路的组成和功能。基于其他小组和我们自己的工作，我们假设细胞外引导信号在生长锥内通过由脂质信号分子磷脂酰肌醇 (PI) 3,4,5-三磷酸 (PIP3) 组成的正反馈环路不对称放大，脂质激酶 PI-3 激酶 (PI3K)、Rho GTPase Rac 和肌动蛋白动力学。此外，我们提出 Ca2+ 在生长锥中与 PIP3 形成正反馈循环，促进 PIP3 和 Rac 活性的局部积累。为了表征生长锥中这些假定的正反馈环路，我们将在活神经元培养物中使用药理学和分子方法以及创新生物传感器来识别 PIP3-PI3K-Rac-actin 动力学正反馈环路的组成和功能（目标 1） ），以及细胞质 Ca2+ 信号传导对不对称 PIP3 信号放大和生长锥转动的贡献（目标 2）。总的来说，该提案中描述的工作将为局部引导提示信号如何放大以及如何促进生长锥对称性破坏提供新的见解，而生长锥对称性破坏是转向和生长到适当的突触目标所需的。