Cytoskeletal Dynamics in Neuronal Dendrites

描述：一个功能性的神经系统既需要树突棘的适当发育，也需要树突棘在整个生命过程中的功能可塑性。由于树突棘是海马和皮层兴奋性神经元突触前轴突的主要接触部位，因此树突棘的结构和功能已被详细研究。肌动蛋白丝（f-actin）在树突棘结构的形成、维持和可塑性中起着重要作用。然而，MTs在脊柱结构中的作用研究很少，因为脊柱被认为缺乏MTs。MTs在树突轴中突出，被认为仅作为细胞内运输的稳定铁路。然而，MTs表现出快速聚合和解聚，称为动态不稳定性。令人惊讶的是，我们发现MTs在整个神经元发育过程中保持动态，并且能够快速地延伸到培养的皮层和海马神经元的树突丝状足和棘中。利用全内反射荧光显微镜（TIRFM），我们发现MT侵袭树突棘可能与棘头的快速形态变化有关。这些发现表明，动态MTs可能在脊柱结构和功能中起重要作用。事实上，许多在MTs上运输的成分（脂质、蛋白质、RNA、细胞器）或与其生长尖端相关的成分将能够通过MTs本身直接进入脊柱。在本提案中，我们将测试动态MT进入树突棘的假设，该假设以受调节的方式发生，并且是脊柱发育和可塑性所必需的。具体而言，我们将：1)表征MT动力学在脊柱形态和成熟中的作用，2)确定MT如何影响突触活动和脊柱可塑性，以及3)研究基于MT的突触成分靶向树突棘。这项工作将为突触发生和突触可塑性提供基本的见解。此外，由于树突棘是许多精神和神经疾病的影响部位，这些研究为基于细胞骨骼的突触功能障碍新疗法带来了希望。公共卫生相关性：有许多发育和成人发病的神经系统疾病，包括智力迟钝、自闭症、癫痫和阿尔茨海默病，都会影响神经元的形状，从而影响大脑中神经元之间的交流。这项研究将确定和表征一种新的细胞内机制，该机制调节神经元特定区域的定向运动成分并控制神经元形状，从而为改善这些疾病的治疗提供潜在的靶点。

DESCRIPTION: A functional nervous system requires both the appropriate development of dendritic spines and their functional plasticity throughout life. Because dendritic spines are the primary sites of contact with presynaptic axons in excitatory neurons of hippocampus and cortex, their structure and function have been studied in great detail. Actin filaments (f-actin) play prominent roles in the formation, maintenance and plasticity of dendritic spine structure. However, the role of MTs in spine architecture has been studied little because spines are thought to be devoid of MTs. Prominent in dendrite shafts, MTs are assumed to function exclusively as stable railways for intracellular transport. However, MTs exhibit bouts of rapid polymerization and depolymerization, termed dynamic instability. Surprisingly, we discovered that MTs remain dynamic throughout neuronal development and are capable of rapidly extending into and out of dendritic filopodia and spines of cultured cortical and hippocampal neurons. Using total internal reflection fluorescence microscopy (TIRFM), we show that MT invasion of dendritic spines can be associated with rapid morphological changes of the spine head. These findings suggest that dynamic MTs may be playing an important role in spine structure and function. Indeed, many of the components that are either transported on MTs (lipids, proteins, RNA, organelles) or are associated with their growing tips would be capable of directly entering spines via MTs themselves. In this proposal we will test the hypothesis that dynamic MT entry into dendritic spines occurs in a regulated fashion and is required for spine development and plasticity. Specifically, we will: 1) Characterize the role of MT dynamics in spine morphology and maturation, 2) Determine how MTs affect synaptic activity and spine plasticity, and 3) Investigate MT-based targeting of synaptic components to dendritic spines. This work will provide fundamental insights into synaptogenesis and synaptic plasticity. Furthermore, because dendritic spines are the sites that are affected in numerous psychiatric and neurological diseases these studies hold promise for novel cytoskeletal-based therapies for synaptic dysfunction. PUBLIC HEALTH RELEVANCE: There are many developmental and adult onset neurological diseases, including mental retardation, autism, epilepsy, and Alzheimer's disease, that affect neuronal shape and therefore communication between neurons in the brain. This research will identify and characterize a novel intracellular mechanism that regulates directed movement of components to specific regions of the neuron and controls neuronal shape, thereby providing potential targets for therapies directed at ameliorating these diseases.