Structural Mechanisms in Semaphorin Signaling

描述(由申请人提供)：信号素信号作为神经、免疫和心血管系统的发展和稳态的寻路控制。信号素的多效性功能是由其细胞表面受体丛状蛋白介导的，在许多情况下还受到辅助受体神经粘连蛋白的辅助。信号素及其受体是糖蛋白的大家族，它们各自的结构和功能在整个动物界都是保守的。信号素信号的失调与许多病理情况有关，包括肿瘤血管生成和进展、神经退行性疾病和多发性硬化症。信号素信号的调控具有治疗的潜力，但由于缺乏有关信号素受体识别的结构信息和信号素受体的激活，因而受到限制。我们提出了三个具体的目的来阐明Semaphorin信号转导的分子机制：1)描述类特异性Semaphorin-Plexin识别的基础；2)阐明Neuropilins在组装3类Semaphorin信号复合体中的作用；3)了解Plexin自身抑制的模式和由Semaphorin结合引起的Plexin构象变化。重组蛋白表达和工程、X射线结晶学、等温滴定热法(ITC)以及生物物理和细胞分析将被用于实现这些特定的目标。信号素及其受体的结构信息可以作为设计潜在应用的基础，例如在癌症治疗中的抗血管生成和抗转移，以及损伤部位的定向神经生长。我们的研究团队经验丰富，在类似这项拟议研究的项目中有着良好的记录。这项研究的结构信息将是非常新颖的，并可能为信号素领域的新的生化和细胞生物学研究奠定基础。

DESCRIPTION (provided by applicant): Semaphorins signaling serves as a path-finding control for the development and homeostasis of the nervous, immune, and cardiovascular systems. The pleiotropic functions of Semaphorins are mediated by their cell surface receptors Plexins, and in many cases aided by the co-receptors Neuropilins. Semaphorins and their receptors are large families of glycoproteins whose respective structures and functions are conserved across the animal kingdom. Dysregulation of Semaphorin signaling has been associated with many pathological conditions, including tumor angiogenesis and progression, neurodegenerative diseases, and multiple sclerosis. The modulation of Semaphorin signaling has therapeutic potential, but is limited by the lack of structural information on Semaphorin-receptor recognition and the activation of Semaphorin receptors. We propose three specific aims to elucidate the molecular mechanisms in Semaphorin signaling: 1) Delineate the basis of class-specific Semaphorin- Plexin recognition; 2) Elucidate the role of Neuropilins in the assembly of class 3 Semaphorin signaling complexes; 3) Understand the mode of Plexin auto-inhibition and the Plexin conformational change induced by Semaphorin binding. Recombinant protein expression and engineering, X-ray crystallography, isothermal titration calorimetry (ITC), and biophysical and cellular assays will be used to accomplish these specific aims. The structural information about Semaphorins and their receptors can serve as a basis for designing potential applications such as anti-angiogenesis and anti- metastasis in cancer treatments, and directional nerve growth at the injury sites. Our research team is highly experienced and has a track record in projects similar to this proposed study. The structural information from this study will be highly novel, and likely will lay the groundwork for novel biochemical and cell biological research in the Semaphorin field.