Investigating the Role and Regulation of the MAP7 Family Proteins in Axonal Morphogenesis and Function

项目摘要 微管是一种蛋白质聚合物，对于神经细胞的形态发生是必不可少的 发展。微管的组装和功能依赖于晶格结合微管的调节 蛋白质(MAP)。许多已知的MAP影响微管的稳定性和细胞器的运输，其中一些 与神经退行性变高度相关。这项拟议的研究将调查一系列独特的地图 它与微管和运动蛋白Kinesin-1相互作用。我们最近对其创始成员的研究 MAP7首次展示了这一鲜为人知的图谱的神经功能。MAP7是 发育调节促进背根神经节感觉神经元轴突的形成 (DRG)。利用原代培养的神经细胞，我们发现MAP7调节分支的形成和生长。 进一步的细胞生物学分析表明，MAP7调节微管稳定性和Kinesin-1介导的 细胞器运输是轴突形态发生和功能的两个关键过程。最近，我们扩大了 我们在几个方向上的研究。首先，我们分析了另一个MAP7D1，一个最接近的MAP7同源物，发现 它与MAP7在培养上具有相似的性质和多余的功能。第二，我们开发了一种新的检测方法 显示MAP7在调节枝条生长过程中的运输方面的潜在作用。第三，在MAP7的研究中 小鼠突变体中，我们发现了MAP7在伤害性感受中潜在的新作用。根据这些发现，我们 假设MAP7家族蛋白在轴突分支中提供了一种新的机制并发挥多种作用 调节细胞器运输的发育和功能。为了验证这一假设，我们问了三个问题：1) MAP7/MAP7D1是否都是DRG神经元分支发育所必需的？2)MAP7是如何调节的 枝条生长和伤害性感受的细胞器运输？3)伤害性感受功能是MAP7所特有的吗 DRG神经元的表达及其与Kinesin-1的相互作用回答这些问题不仅会扩大 我们对这一新的映射家族的知识，也解决了关于微管的基本问题- 基于神经元发育和功能的细胞内转运。更重要的是，我们建议的研究 随着对背根节感觉神经元的关注，我们将能够探索运输调节在伤害性感受和 从而使我们更接近医学上相关的问题，如疼痛。考虑到伤害的重要性和 疼痛对人类健康的影响，我们建议的研究重点是一个基本的细胞生物学问题，因此 与美国国立卫生研究院调查大脑功能和紊乱的任务高度相关。

PROJECT ABSTRACT Microtubules are protein polymers that are essential for neuronal cell morphogenesis during development. Microtubule assembly and function rely on the regulation of lattice-bound microtubule-associated proteins (MAPs). Many known MAPs influence microtubule stability and organelle transport, and some of them are highly associated with neurodegeneration. The proposed study will investigate a unique family of MAPs that interact with both microtubules and the motor protein kinesin-1. Our recent study of its founding member MAP7 provides the first demonstration of the neuronal function of this less-well understood MAP. MAP7 is developmentally regulated to promote axonal branch formation of sensory neurons in the dorsal root ganglion (DRG). Using primary neuronal cell culture, we have found that MAP7 regulates branch formation and growth. Further cell biological analysis has revealed that MAP7 regulates microtubule stability and kinesin-1-mediated organelle transport, two processes that are critical to axonal morphogenesis and function. Recently, we expand our studies in several directions. First, we analyzed another MAP7D1, a closest MAP7 homolog and found that it has similar properties and redundant function as MAP7 in culture. Second, we developed a new assay to show the potential role of MAP7 in regulating transport during branch growth. Third, in the study of MAP7 mouse mutants, we found a potential new role of MAP7 in nociception. Following these findings, we hypothesize that the MAP7 family proteins provide a novel mechanism and play multiple roles in axonal branch development and function by regulating organelle transport. To test this hypothesis, we ask three questions: 1) Are both MAP7/MAP7D1 required for branch development of DRG neurons? 2) How does MAP7 regulate organelle transport for branch growth and nociception? 3) is the nociception function specific for MAP7 expressed in DRG neurons and its interaction with kinesin-1? Answering these questions will not only expand our knowledge of this novel family of MAPs but also address fundamental questions regarding microtubule- based intracellular transport in neuronal development and function. More importantly, our proposed studies with a focus on DRG sensory neurons will allow us to explore the role of transport regulation in nociception and thus bring us closer to medically relevant problems, such as pain. Given the importance of nociception and pain in human health, our proposed studies with a focus on a fundamental cell biological problem are thus highly relevant to the NIH mission of investigating brain functions and disorders.