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

项目摘要 微管是蛋白质聚合物，其在神经细胞发育过程中对于神经细胞形态发生是必需的。 发展微管的组装和功能依赖于对晶格结合微管相关蛋白的调节。 蛋白质（MAPs）。许多已知的MAP影响微管稳定性和细胞器运输，其中一些MAP影响微管稳定性和细胞器运输。 与神经退化密切相关拟议的研究将调查一个独特的家庭地图 与微管和运动蛋白驱动蛋白1相互作用。我们最近对其创始成员的研究 MAP 7首次证明了这种不太清楚的MAP的神经功能。MAP 7是 发育调节以促进背根神经节中感觉神经元的轴突分支形成 （DRG）。使用原代神经元细胞培养，我们发现MAP 7调节分支的形成和生长。 进一步的细胞生物学分析显示，MAP 7调节微管稳定性，并且驱动蛋白-1介导的细胞凋亡可能与MAP 7的表达有关。 细胞器运输，这两个过程对轴突形态发生和功能至关重要。最近，我们扩大了 我们的研究在几个方向。首先，我们分析了另一个MAP 7 D1，一个最接近的MAP 7同源物，发现 它与培养中的MAP 7具有相似的性质和冗余功能。其次，我们开发了一种新的检测方法， 显示了MAP 7在分支生长过程中调节运输的潜在作用。第三，在对MAP 7的研究中， 小鼠突变体，我们发现了MAP 7在伤害感受中的潜在新作用。根据这些发现，我们 假设MAP 7家族蛋白提供了一种新的机制，并在轴突分支中发挥多种作用 通过调节细胞器运输来发育和发挥功能。为了验证这个假设，我们提出三个问题：1） MAP 7/MAP 7 D1是DRG神经元分支发育所必需的吗？2)MAP 7如何调节 分支生长和伤害感受的细胞器运输？3)是MAP 7特异性的伤害感受功能 表达的DRG神经元及其相互作用与驱动蛋白1？回答这些问题不仅会扩大 我们对这个新的MAP家族的了解，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运输。更重要的是，我们的研究计划 以DRG感觉神经元为重点，将使我们能够探索运输调节在伤害性感受中的作用， 从而使我们更接近医学相关的问题，如疼痛。鉴于伤害感受的重要性， 疼痛在人类健康，我们提出的研究重点是一个基本的细胞生物学问题，因此， 与NIH调查大脑功能和疾病的使命高度相关。

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.