Transduction Mechanisms Mediating Nerve Growth Cone Guidance

介导神经生长锥引导的转导机制

• 批准号: 8134805
• 负责人: John Richard Henley
• 金额: $ 33.81万
• 依托单位: MAYO CLINIC ROCHESTER
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8134805
• 关键词: Address; Adhesions; Axon; Biological Assay; Biological Models; Biosensor; Brain-Derived Neurotrophic Factor; Cell membrane; Cell physiology; Cells; Chemotactic Factors; Chemotaxis; Chimeric Proteins; Complex; Cues; DNA Sequence Rearrangement; Detection; Dominant-Negative Mutation; Dyes; Dynamin; ECM receptor; Endocytosis; Exocytosis; Extracellular Matrix; Feedback; Goals; Growth Cones; Image; Immunoassay; In Vitro; Injury; Integrins; Label; Life; Link; Mediating; Membrane; Methods; Microscopic; Modeling; Molecular; Myelin; Myelin Associated Glycoprotein; Natural regeneration; Nerve; Nervous System Trauma; Nervous system structure; Neurodegenerative Disorders; Neurons; Oligonucleotides; Phosphatidylinositols; Phosphotransferases; Process; Proteins; Receptor Activation; Recovery of Function; Recycling; Regulation; Research; Role; Signal Transduction; Signal Transduction Pathway; Spinal; Surface; Therapeutic; Total Internal Reflection Fluorescent; Vesicle; Xenopus; axon growth; axon guidance; base; cell growth regulation; cellular imaging; extracellular; fluorescence imaging; human NTN1 protein; in vivo; insight; mutant; nervous system development; netrin-1; novel; phosphatidylinositol 3,4,5-triphosphate; prevent; public health relevance; receptor; release factor; trafficking

DESCRIPTION (provided by applicant): The growth cone of developing axons guides axon extension through the extracellular matrix (ECM) by sensing gradients of environmental guidance cues that initiate attractive or repulsive steering. Chemotactic growth cone guidance is also important in the context of nervous system injury, as factors released from the breakdown of myelin may act as chemorepellents and inhibit axon elongation, thereby preventing functional recovery. Understanding the molecular mechanisms that mediate growth cone guidance could provide important insights for developing strategies to enhance regeneration after injury or neurodegenerative disease. Cytoplasmic Ca2+ signals mediate the action of many guidance cues, but the link between surface receptor activation and Ca2+ signaling is largely unknown. Likewise, an understanding of the cellular processes underlying growth cone chemotaxis remains incomplete. Current models rely heavily on cytoskeletal rearrangements, but in vivo studies have demonstrated that regulated adhesion to the ECM is also critical for proper guidance. The goal of the proposed research is to define the transduction mechanisms underlying the chemotactic guidance of axonal growth cones. Specifically, we aim to define the intracellular signals that mediate growth cone detection of extracellular guidance cues, the interactions between early signal transduction pathways, and the regulation of downstream effector processes that control the direction of axon extension. Our preliminary findings have led us to establish a CENTRAL HYPOTHESIS that growth cone detection of guidance cues is mediated by polarized phosphoinositide 3-kinase (PI3K) and Akt signaling at the surface membrane, which triggers local Ca2+ signals and stimulates endocytic and exocytic machinery to redistribute receptors for ECM and guidance cues asymmetrically at the growth cone surface and initiate chemotactic guidance. The proposal is organized into four interrelated specific aims that will define the following: first, the role of PI3K/Akt signaling in mediating growth cone chemotaxis; second, how PI3K/Akt signaling activates Ca2+ guidance signals in the growth cone; third, how PI3K/Akt and Ca2+ signaling regulate vesicle dynamics during growth cone turning; and fourth, how PI3K/Akt and Ca2+ signaling regulate trafficking of integrin and guidance receptors during growth cone turning. This study will provide novel insights into the early signals that mediate the detection of guidance cues, the amplification of guidance signals, and the regulation of cellular machinery that controls membrane dynamics and the redistribution of surface receptors during chemotactic growth cone guidance. PUBLIC HEALTH RELEVANCE: In the developing nervous system the growing tip of nerve cells extends through a complex environmental matrix to the appropriate target cells by sensing gradients of guidance cues that initiate attractive or repulsive steering. This guidance is also important in the context of nervous system injury, as factors released from the breakdown of myelin may act as repellents and inhibit elongation, thereby preventing functional recovery. The goal of this research is to define signals that mediate the detection of guidance cues and determine how these signals regulate cellular processes to control the direction of extension. The findings will contribute to our understanding of the development of the nervous system and provide insights into potential therapeutic approaches for promoting regeneration after neurodegenerative disease or injury.

描述(申请人提供)：发育中轴突的生长锥体通过感知启动吸引力或排斥性转向的环境引导线索的梯度，通过细胞外基质(ECM)引导轴突延伸。在神经系统损伤的情况下，趋化生长锥指导也很重要，因为髓鞘分解释放的因子可能作为化学反应物，抑制轴突延长，从而阻止功能恢复。了解调节生长锥引导的分子机制可以为制定促进损伤或神经退行性疾病后再生的策略提供重要的见解。细胞质中的钙信号介导了许多引导信号的作用，但表面受体激活和钙信号之间的联系在很大程度上还不清楚。同样，对生长锥体趋化作用背后的细胞过程的理解仍然不完整。目前的模型严重依赖于细胞骨架重排，但体内研究表明，调节与细胞外基质的黏附也是适当指导的关键。本研究的目的是明确轴突生长锥体趋化导向的转导机制。具体地说，我们的目标是定义细胞内信号，这些信号介导细胞外引导信号的生长锥检测，早期信号转导通路之间的相互作用，以及控制轴突延伸方向的下游效应器过程的调节。我们的初步发现导致我们建立了一个中心假设，即生长锥对指导信号的检测是由表面膜上极化的磷脂酰肌醇3-激酶(PI3K)和Akt信号介导的，该信号触发局部钙信号并刺激内、外分泌机制在生长锥表面不对称地重新分配ECM和指导线索的受体，并启动趋化指导。该提案被组织成四个相互关联的具体目标，它们将定义以下内容：第一，PI3K/Akt信号在介导生长锥趋化中的作用；第二，PI3K/Akt信号如何激活生长锥中的钙引导信号；第三，PI3K/Akt和钙+信号如何调节生长锥转动过程中的囊泡动力学；第四，PI3K/Akt和钙+信号如何调节生长锥转动过程中整合素和导向受体的运输。这项研究将为早期信号提供新的见解，这些信号介导了指导信号的检测、指导信号的放大，以及在趋化生长锥指导过程中控制膜动力学和表面受体重新分布的细胞机制的调节。 与公共健康相关：在发育中的神经系统中，神经细胞的生长尖端通过感知引导信号的梯度，通过复杂的环境基质延伸到适当的目标细胞，这些引导信号启动了吸引或排斥的转向。这一指导在神经系统损伤的情况下也很重要，因为髓鞘分解释放的因子可能起到驱避剂的作用，抑制伸长，从而阻止功能恢复。这项研究的目标是定义调节引导线索检测的信号，并确定这些信号如何调节细胞过程以控制延伸的方向。这些发现将有助于我们了解神经系统的发育，并为促进神经退行性疾病或损伤后再生的潜在治疗方法提供见解。