Soluble Neuregulins in Neuromuscular and Peripheral Nerve Development

描述（由申请人提供）：神经调节蛋白（NRG）是一类神经源性生长和分化因子，通过可溶性、肝素结合和膜锚定的选择性剪接形式“靶向”轴神经胶质界面和神经肌肉接头（NMJ）。它们促进外周和中央胶质细胞的增殖、迁移、存活和髓鞘形成。在 NMJ 中，它们的作用不太清楚，但肝素结合NRG1 的形式在不同的发育阶段在 NMJ 的基底层内积累，并诱导乙酰胆碱受体，这表明它们可以促进突触强度，因为轴突与肌肉和雪旺细胞靶标非常接近，因此很难确定 NRG1 对肌肉和神经的直接和间接影响。我们的实验室重点研究可溶性肝素结合形式的 NRG1。轴突响应雪旺细胞和肌肉源性神经营养因子（如 BDNF 和 GDNF），并且该通路受蛋白激酶 C 调节。一旦释放，NRG1 通过与硫酸乙酰肝素蛋白聚糖 (HSPG) 的高度特异性相互作用而集中在神经内和 NMJ 处。在这里，我们将探讨 NRG1 如何通过两种连续机制促进鸡和小鼠胚胎中的周围神经和 NMJ 发育。 (2)神经营养因子诱导的 PKC 信号传导一旦从轴突释放，NRG1 将通过发育表达的硫酸乙酰肝素蛋白多糖 (HSPG) 定位到细胞外基质中积累的位点。在这些研究的一个重要部分中，我们还将测试一种新的治疗方法，以利用轴胶质细胞和神经肌肉接头进行生物治疗。 NRG1 的肝素结合结构域作为特定的靶向基序。迄今为止，还没有针对周围和中枢神经系统疾病的有效治疗方法，即开发使用神经系统形成所需的生长因子的生物驱动疗法。该提案将尝试通过提高对正常发育的了解和改进针对神经系统内的新型疗法的方法来克服开发此类疗法的一些主要限制。 公共健康相关性：了解调节神经调节蛋白在周围神经和神经肌肉接头处的释放和定位的机制对于设计针对周围神经和神经肌肉疾病（例如神经病和肌萎缩侧索硬化症，以及中枢神经系统疾病，例如多发性硬化症和精神分裂症）的有效治疗方法至关重要。治疗方法包括促进神经调节蛋白或神经营养蛋白信号传导，和/或通过激活PKC-4 信号传导。我们的研究还测试了我们发明的更通用的“靶向”系统，该系统通过其独特的硫酸乙酰肝素成分有效地向特定细胞类型提供治疗。

DESCRIPTION (provided by applicant): The neuregulins (NRGs) are a family of neuronally-derived growth and differentiation factors that 'target" the axoglial interface and neuromuscular junctions (NMJs) through both soluble, heparin-binding and membrane anchored alternatively spliced forms. They promote proliferation, migration, survival, and myelination of both peripheral and central glia. At the NMJ, their role is less clear, but heparin-binding forms accumulate within the basal lamina of NMJs at distinct developmental stages and induce acetylcholine receptors, suggesting that they promote synaptic strength. Given the close proximity of the axon to both muscle and Schwann cell targets, the direct and indirect effects of NRG1 on muscle and nerve have been difficult to establish. Our laboratory focuses on the soluble, heparin-binding forms of NRG1. We found that soluble forms of NRG1 are rapidly released from both sensory and motor neuron axons in response to Schwann cell and muscle-derived neurotrophic factors such as BDNF and GDNF, and that this pathway is regulated by protein kinase C. Once released, NRG1 becomes concentrated within the nerve and at NMJs through highly specific interactions with heparan sulfate proteoglycans (HSPGs). Here, we will explore how NRG1 promotes peripheral nerve and NMJ development in both chick and mouse embryos through two sequential mechanisms. (1) Regulated release from axons by Schwann cell and muscle-derived neurotrophic factors, (2) Neurotrophic factor-induced PKC signaling. Once released from axons, NRG1 will be localized to sites where it accumulates in the extracellular matrix through developmentally-expressed heparan-sulfate proteoglycans (HSPGs). In an important part of these studies, we will also test a novel therapeutic method to target biological therapeutics to axoglial and neuromuscular junctions using NRG1's heparin-binding domain as a specific targeting motif. Relevance: To date there are few effective treatments for diseases of the peripheral and central nervous systems. A promising means to overcome this is to develop biologically-driven therapeutics that use growth factors required for nervous system formation. This proposal will attempt to overcome some off the major limitations in developing such therapeutics through an improved understanding of normal development and improved ways to target novel therapeutics within the nervous system. PUBLIC HEALTH RELEVANCE: Understanding the mechanisms that regulate the release and localization of neuregulin at the peripheral nerve and neuromuscular junction will be critical to design effective therapeutics for diseases of peripheral nerve and neuromuscular disorders, such as neuropathy andALS,aswellasCNSdisorders,suchasmultiplesclerosisandschizophrenia.Treatmentscould consist of promoting neuregulin or neurotrophin signaling, and/or promoting neuregulin release through activation of PKC-4 signaling. Our studies also test a more general 'targeting' system we invented that effectively delivers therapeutics to specific cell types through their unique heparan sulfate composition.