Unravelling the mechanism of complement activation via the lectin pathway

通过凝集素途径揭示补体激活机制

• 批准号: MR/K011715/1
• 负责人: Stephen Perkins
• 金额: $ 62.25万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=MR%2FK011715%2F1
• 关键词: Unravelling; mechanism; complement; activation; via

Our immune system is vital to protect us from all types of bacterial, fungal and viral infections. There are two major types of immune defence, called "innate" and "adaptive" (based on antibodies that recognise pathogens). Although lesser known, innate immunity serves as a first line of defence by both destroying invading pathogens directly and helping the adaptive immune system to distinguish between what is foreign (a bacterial cell) and what is self (host cell). Blood proteins called "complement" act to recognise and destroy invading foreign bacteria. In order to be effective, complement requires highly specific recognition and activation mechanisms so that it only activates when required and does not start to attack host tissues. In the "lectin pathway", a protein called MBL specifically recognises arrays of sugars found on bacterial pathogens but not present on our own cells. This binding then triggers a change in a second protein called MASP, causing it to switch from an inactive to an active form. These two events then lead to activation of other complement proteins, which ultimately trigger formation of a complex in the cell membrane of the bacterium, causing it to burst, as well as stimulating other immune processes and protective functions. Although the lectin pathway is a key part of our immune system, the molecular details of how it works are poorly understood. For example, how MBL and MASP bind to each other is presently unknown as are the changes that lead to MASP activation. However, understanding of these events is crucial for us to comprehend how the healthy body functions and what goes wrong in disease. This knowledge in turn will aid the development of therapeutics aimed at controlling complement activation when things go wrong. For example, following a stroke or heart attack, uncontrolled complement activation destroys host tissues. Being able to block activation temporarily under these circumstances (using medicines) would be highly beneficial. Secondly, a better understanding of complement could facilitate the treatment of patients with immunodeficiencies. A range of common genetic alterations in MBL lead to a broad spectrum of disorders. These include increased susceptibility to infections in early childhood, to instances in adults where adaptive immunity becomes ineffective such as during AIDS or cancer chemotherapy. MBL has become a very good therapeutic target to counteract these threats. We are ideally situated to identify how complement activation occurs. Recently, we have established the solution structure of MBL. We employed a unique approach based on combining detailed information from protein crystallography with new information based on protein scattering, ultracentrifugation and extensive computer modelling calculations. This showed that the MBL molecules are fan-shaped and form an almost flat template for MASP to bind.The aims of this project will result in a new comprehensive understanding of lectin pathway activation: (Aim 1) To start with, we will apply our scattering and crystallography techniques to determine the corresponding structure of MASP. Further, we will identify the changes that take place within the MASP, causing it to self-activate. (Aim 2) We have recently determined the structure of a complex between small fragments of MBL and MASP. We will use this structure to make test models for the entire MBL-MASP complex. By testing these models against new scattering and ultracentrifugation data, we will establish the way in which they bind. (Aim 3) We will determine new crystal structures and use new scattering/ultracentrifugation experiments to see what happens to the structure of MBL when it is modified in genetic diseases. In particular we will clarify why some MBLs over-activate MASP while others result in no MASP activation. In this way we will be able to elucidate the changes that trigger MASP activation when MBL binds to a bacterial cell.

我们的免疫系统对于保护我们免受所有类型的细菌，真菌和病毒感染至关重要。有两种主要类型的免疫防御，称为“先天性”和“适应性”（基于识别病原体的抗体）。虽然不太为人所知，但先天免疫作为第一道防线，既直接摧毁入侵的病原体，又帮助适应性免疫系统区分外来（细菌细胞）和自身（宿主细胞）。被称为“补体”的血液蛋白质可以识别并摧毁入侵的外来细菌。为了有效，补体需要高度特异性的识别和激活机制，以便它仅在需要时激活，而不会开始攻击宿主组织。在“凝集素途径”中，一种名为MBL的蛋白质特异性识别细菌病原体上发现的糖阵列，但不存在于我们自己的细胞中。这种结合然后触发了第二种蛋白质MASP的变化，使其从非活性形式转变为活性形式。这两个事件然后导致其他补体蛋白的激活，最终触发细菌细胞膜中复合物的形成，导致其破裂，以及刺激其他免疫过程和保护功能。虽然凝集素途径是我们免疫系统的关键部分，但对其如何工作的分子细节知之甚少。例如，MBL和MASP如何彼此结合目前是未知的，导致MASP活化的变化也是未知的。然而，了解这些事件对于我们理解健康的身体如何运作以及疾病中出现了什么问题至关重要。这些知识反过来将有助于开发旨在控制补体激活的治疗方法。例如，中风或心脏病发作后，不受控制的补体激活会破坏宿主组织。在这种情况下，能够暂时阻止激活（使用药物）将是非常有益的。其次，更好地了解补体可以促进免疫缺陷患者的治疗。MBL中的一系列常见遗传改变导致广泛的疾病。这些因素包括儿童早期对感染的易感性增加，以及成人适应性免疫变得无效的情况，如艾滋病或癌症化疗期间。MBL已经成为对抗这些威胁的一个非常好的治疗靶点。 我们处于理想的位置，以确定如何补体激活发生。最近，我们建立了MBL的溶液结构。我们采用了一种独特的方法，该方法基于将来自蛋白质晶体学的详细信息与基于蛋白质散射、超浓缩和广泛的计算机建模计算的新信息相结合。本项目的目的是对凝集素途径的激活有一个新的全面的认识：（目的1）首先，我们将应用散射和晶体学技术确定MASP的相应结构。此外，我们将识别MASP内发生的变化，使其自激活。(Aim 2）我们最近确定了MBL和MASP小片段之间的复合物的结构。我们将使用这种结构来为整个MBL-MASP复合物制作测试模型。通过测试这些模型对新的散射和超散射数据，我们将建立它们的结合方式。(Aim 3）我们将确定新的晶体结构，并使用新的散射/超离心实验来观察当MBL在遗传疾病中被修饰时，它的结构会发生什么变化。特别地，我们将阐明为什么一些MBL过度活化MASP，而其他MBL不导致MASP活化。以这种方式，我们将能够阐明当MBL结合细菌细胞时触发MASP活化的变化。

项目成果

Non-linearity of the collagen triple helix in solution and implications for collagen function.

• DOI: 10.1042/bcj20170217
• 发表时间: 2017-06-16
• 期刊: The Biochemical journal
• 作者: Walker KT;Nan R;Wright DW;Gor J;Bishop AC;Makhatadze GI;Brodsky B;Perkins SJ
• 通讯作者: Perkins SJ

A solution structure analysis reveals a bent collagen triple helix in the complement activation recognition molecule mannan-binding lectin.

• DOI: 10.1016/j.jbc.2022.102799
• 发表时间: 2023-02
• 期刊: JOURNAL OF BIOLOGICAL CHEMISTRY
• 影响因子: 4.8
• 作者: Iqbal, Hina;Fung, Ka Wai;Gor, Jayesh;Bishop, Anthony C.;Makhatadze, George I.;Brodsky, Barbara;Perkins, Stephen J.
• 通讯作者: Perkins, Stephen J.

Atomistic modelling of scattering data in the Collaborative Computational Project for Small Angle Scattering (CCP-SAS).

• DOI: 10.1107/s160057671601517x
• 发表时间: 2016-12-01
• 期刊: Journal of applied crystallography
• 影响因子: 6.1
• 作者: Perkins SJ;Wright DW;Zhang H;Brookes EH;Chen J;Irving TC;Krueger S;Barlow DJ;Edler KJ;Scott DJ;Terrill NJ;King SM;Butler PD;Curtis JE
• 通讯作者: Curtis JE

Flexibility in Mannan-Binding Lectin-Associated Serine Proteases-1 and -2 Provides Insight on Lectin Pathway Activation.

• DOI: 10.1016/j.str.2016.12.014
• 发表时间: 2017-02-07
• 期刊: Structure (London, England : 1993)
• 作者: Nan R;Furze CM;Wright DW;Gor J;Wallis R;Perkins SJ
• 通讯作者: Perkins SJ

Molecular Interactions between Complement Factor H and Its Heparin and Heparan Sulfate Ligands.

• DOI: 10.3389/fimmu.2014.00126
• 发表时间: 2014
• 期刊: Frontiers in immunology
• 影响因子: 7.3
• 作者: Perkins SJ;Fung KW;Khan S
• 通讯作者: Khan S