Signaling and Regulation Mechanisms of Plexin

Plexin 的信号传导和调节机制

• 批准号: 9314577
• 负责人: Xuewu Zhang
• 金额: $ 32.12万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-30 至 2019-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9314577
• 关键词: Active Sites; Address; Adopted; Adult; Affinity; Autoimmune Diseases; Binding; Binding Sites; Biological Assay; C-terminal; Cardiovascular system; Cell Surface Receptors; Cell membrane; Cell surface; Cells; Complex; Crystallization; DH Domain; Development; Dimerization; Disease; Family; Family member; Foundations; GTPase-Activating Proteins; Goals; Guanine Nucleotide Exchange Factors; Guanosine Triphosphate; Guanosine Triphosphate Phosphohydrolases; Homeostasis; Hydrolysis; Immune response; Injury; Laboratories; Length; Liposomes; Malignant Neoplasms; Mediating; Membrane; Modeling; Molecular Conformation; Monomeric GTP-Binding Proteins; Mutation Analysis; N-terminal; Natural regeneration; Nature; Nerve Regeneration; Neuraxis; Neurons; Pathway interactions; Process; Proteins; Regulation; Reporting; Research Design; Resolution; Rho Factor; Role; Semaphorins; Signal Pathway; Signal Transduction; Signaling Protein; Structure; Tertiary Protein Structure; Testing; Transducers; Tyrosine Phosphorylation; X-Ray Crystallography; angiogenesis; axon growth; axon guidance; base; bone; design; dimer; extracellular; fighting; immunoregulation; improved; malignant neurologic neoplasms; nervous system development; nervous system disorder; plexin; public health relevance; receptor; targeted treatment; Active Sites; Address; Adopted; Adult; Affinity; Autoimmune Diseases; Binding; Binding Sites; Biological Assay; C-terminal; Cardiovascular system; Cell Surface Receptors; Cell membrane; Cell surface; Cells; Complex; Crystallization; DH Domain; Development; Dimerization; Disease; Family; Family member; Foundations; GTPase-Activating Proteins; Goals; Guanine Nucleotide Exchange Factors; Guanosine Triphosphate; Guanosine Triphosphate Phosphohydrolases; Homeostasis; Hydrolysis; Immune response; Injury; Laboratories; Length; Liposomes; Malignant Neoplasms; Mediating; Membrane; Modeling; Molecular Conformation; Monomeric GTP-Binding Proteins; Mutation Analysis; N-terminal; Natural regeneration; Nature; Nerve Regeneration; Neuraxis; Neurons; Pathway interactions; Process; Proteins; Regulation; Reporting; Research Design; Resolution; Rho Factor; Role; Semaphorins; Signal Pathway; Signal Transduction; Signaling Protein; Structure; Tertiary Protein Structure; Testing; Transducers; Tyrosine Phosphorylation; X-Ray Crystallography; angiogenesis; axon growth; axon guidance; base; bone; design; dimer; extracellular; fighting; immunoregulation; improved; malignant neurologic neoplasms; nervous system development; nervous system disorder; plexin; public health relevance; receptor; targeted treatment

DESCRIPTION (provided by applicant): Plexins are the cell surface receptors of semaphorins. Plexin-mediated semaphorin signaling is essential for processes such as the development of the nervous system and the cardiovascular system and regulation of immune responses and bone homeostasis. Malfunction of plexins has been associated with neurological disorder and cancer. Understanding how plexins function will pave the way for developing targeted therapeutics for fighting the associated diseases and improving neuronal regeneration after injury. The plexin intracellular region contains a GTPase Activating Protein (GAP) domain that is essential for function. In the previous period, we have identified the small GTPase Rap as the authentic substrate for the plexin GAP domain, and have determined the structural basis for how the GAP domain is activated by semaphorin-induced dimerization and how it inactivates Rap through a non-canonical catalytic mechanism. Objectives. To study additional layers of regulation mechanisms of plexins, and mutual regulation between plexins and several of their key binding partners. Research Design. Based on a new crystal structure of ours, we will first analyze the role of the inhibitory dimer in plexin regulation, a long-standing question in the fiel. Plexin signaling requires not only its RapGAP activity, but also its ability to assemble and contro the activity of a multi-protein signaling complex at the plasma membrane. Many proteins interact with plexins, but the structural basis of their actions is largely unknown. We will focus on some of the essential binding partners, address the questions how they bind plexin and exert mutual regulation with plexins. In Aim 1 we will test an inhibitory dimer model in plexin regulation. We have determined two crystal structures of PlexinA4, which adopts a new conformation and forms a compact dimer with the GAP active site buried in the dimer interface. We propose that this dimer and the apo dimer structure of the plexin extracellular region reported previously together mediate the autoinhibited dimeric state of full-length plexin on the cell surface. Structure-based mutational analyses will be performed to test this hypothesis. In Aim 2 we will study the basis for the opposite effects of RND1/Rac and RhoD on plexin signaling. The RhoGTPases Rac1 and RND1 interact with plexin and facilitate its binding and activation by semaphorin. In contrast, RhoD inhibits plexin signaling, although it binds plexin in the same mode with similar affinity. Our structure analyses led to a hypothesis that explains this paradox, which will be tested in this aim. In Aim 3 we will analyze the interaction and regulation of FARPs by plexin. FARP1 and FARP2 are two related guanine nucleotide exchange factors (GEFs) that have been shown to interact directly with plexin and make essential contributing to its signaling. We will pursue a structure of the plexin/FARP complex to elucidate the basis for their interaction, and analyze how this interaction helps release the autoinhibition of FARPs.

描述（由申请人提供）：丛蛋白是信号蛋白的细胞表面受体。丛蛋白介导的信号信号对于诸如神经系统发展和心血管系统的发展以及免疫反应和骨稳态的调节至关重要。丛蛋白的故障与神经系统疾病和癌症有关。了解丛蛋白功能将如何为开发靶向治疗剂打击相关疾病并改善受伤后神经元再生的方式铺平道路。丛内细胞内区域包含一个对功能必不可少的GTPase激活蛋白（GAP）结构域。在上一个时期，我们已经将小的GTPase RAP确定为Plexin GAP结构域的真实底物，并确定了如何通过Semaphorin诱导的二聚化激活GAP结构域的结构基础，以及它如何通过非循环催化机制使RAP失活。目标。研究丛蛋白调节机制的其他层，以及丛蛋白与几个关键结合伴侣之间的相互调节。研究设计。基于我们的新晶体结构，我们将首先分析抑制性二聚体在Plexin调节中的作用，这是FIEL中的一个长期存在的问题。 Plexin信号不仅需要其RAPGAP活性，而且还需要其在质膜上组装和捕获多蛋白信号复合物的活性的能力。许多蛋白质与丛蛋白相互作用，但其作用的结构基础在很大程度上未知。我们将重点关注一些基本的结合伙伴，解决它们如何结合丛林并与丛蛋白发挥相互调控的问题。在AIM 1中，我们将测试Plexin调节中的抑制二聚体模型。我们已经确定了Plexina4的两个晶体结构，该结构采用了一种新的构象，并形成一个紧凑的二聚体，而间隙活性位点埋在二聚体界面中。我们提出，丛外区域的该二聚体和APO二聚体结构先前报道了介导细胞表面上全长丛蛋白的自抑制二聚体状态。将进行基于结构的突变分析以检验该假设。在AIM 2中，我们将研究RND1/RAC和RHOD对丛蛋白信号传导的相反影响的基础。 RHOGTPases Rac1和RND1与丛蛋白相互作用，并促进了词素的结合和激活。相反，Rhod抑制了丛信号传导，尽管它以相似亲和力结合了相同模式的丛集。我们的结构分析导致了一个假设，该假设解释了这种悖论，该悖论将在此目标中进行测试。在AIM 3中，我们将通过plexin分析FARP的相互作用和调节。 FARP1和FARP2是两个相关的鸟嘌呤核苷酸交换因子（GEF），它们已证明可以直接与丛蛋白相互作用，并为其信号带来了重要的作用。我们将追求丛/FARP复合物的结构，以阐明其相互作用的基础，并分析这种相互作用如何有助于释放FARP的自身抑制作用。