The Dynamics of Synaptic Component at the Neuromuscular Junction of Living Animal

描述(申请人提供)：我们的长期目标是更好地了解在体内成熟和发育中的突触中神经递质受体密度是如何维持和调节的。我们使用神经肌肉接头(NMJ)作为我们的模型系统，NMJ是运动神经元和肌肉纤维之间的兴奋性胆碱能突触，因为这个突触的疾病对人类健康有重大影响，也因为它为研究体内神经递质受体循环的过程提供了最容易获得的模型系统。直到最近，受体回收一直被认为是中枢神经系统神经递质受体的专有特性，但我们发现，大量的乙酰胆碱受体(AChRs)在内化后被回收到突触后膜上，有助于维持成熟突触上受体的突触后密度。我们将追求两个目标来评估在突触发育和成熟过程中回收的潜在作用，以及两个目标来测试那些强烈参与回收过程的分子的作用。我们重点研究了α-dystrobrevin和α-syntroin在调节AChR在突触后膜上循环中的作用，因为这些蛋白的突变显然与人类神经肌肉传递障碍有关，并且这些基因在小鼠中的突变已被证明显著改变成熟突触上AChR的数量，如果受体循环异常，可能会预期到这一点。了解受体循环的分子基础可能会导致更有效的干预和治疗，从而通过增加神经肌肉疾病中AChR的数量或密度来增加突触传递。此外，受体循环的某些方面似乎对所有细胞都是共同的，因此我们预计这些结果不仅有助于理解神经肌肉连接的发育，而且将为了解受体循环在突触发生和较难到达的中央突触的突触可塑性中的长期作用提供见解。与公共健康相关：神经末梢正下方神经递质受体的积累对于神经冲动到肌肉的健康传递至关重要。这项提议的目的是帮助我们更好地了解这些受体聚集在成熟突触并在突触连接的正常发展过程中形成的方式，并开发出当这些连接因疾病而减弱时加强这些连接的方法。

DESCRIPTION (provided by applicant): Our long term goal is to better understand how neurotransmitter receptor density is maintained and regulated at mature and developing synapses in vivo. We are using the neuromuscular junction (NMJ), an excitatory cholinergic synapse between motor neurons and muscle fibers as our model system, because of the significant impact on human health of disorders at this synapse and because it provides the most accessible model system to study the process of neurotransmitter receptor recycling in vivo. Until recently receptor recycling was thought to be an exclusive property of neurotransmitter receptors in the central nervous system, but we discovered that significant numbers of acetylcholine receptors (AChRs) are recycled back onto the postsynaptic membrane after internalization, contributing to the maintenance of the postsynaptic density of receptors at mature synapses. We will pursue two goals to assess potential roles for recycling during synaptic development and in maturity and two goals to test the roles of molecules that are strong candidates for participation in the recycling process. We have focused on the roles of alpha-dystrobrevin and alpha-syntrophin in regulating the recycling of AChR onto the postsynaptic membrane because mutations in these proteins are clearly associated with human disorders of neuromuscular transmission, and mutations of these genes in mice have been demonstrated to dramatically alter the number of AChR at mature synapses, as might be expected if receptor recycling was aberrant. Understanding the molecular basis of receptor recycling could lead to more effective intervention and therapy that could increase synaptic transmission by increasing AChR number or density in neuromuscular diseases. Furthermore, it seems likely that some aspects of receptor recycling will be common to all cells, so we expect that these results will be useful not only in understanding the development of the neuromuscular junction, but will provide insights into the long-term role of receptor recycling in synaptogenesis and synaptic plasticity at less accessible central synapses. PUBLIC HEALTH RELEVANCE: The accumulation of neurotransmitter receptors directly underneath nerve terminals is essential for healthy transmission of nerve impulses to muscle. The goal of this proposal is to help us better understand the ways by which these receptors are clustered at mature synapses and shaped during the normal development of synaptic connections and develop ways to strengthen these connections when they are weakened by disease.