Structural mechanism of integrin-mediated TGF-b activation

概述/摘要：TGF-β驱动导致肺和气道纤维化的纤维炎症过程。的 本项目的长期目标是深入了解TGF-β活性的调节， 纤维化肺病的新策略和治疗方法。很少有有效的疗法来治疗慢性 肺纤维化和炎性疾病。细胞因子TGF-β是纤维化的中心介质， 病理性炎症，并且是纤维化肺病的潜在治疗靶点。然而，实际 靶向TGF-β 1本身或其受体的效用受到啮齿动物、灵长类动物和哺乳动物中观察到的毒性风险的限制。 人类靶向TGF-β 1的纤维炎性作用的更特异性方法是高度期望的。一 一种更有前景的针对TGF-β局部作用的方法是针对其“激活”，因为它总是 以潜伏形式（L-TGF-β）产生，必须被激活才能发挥作用。L-TGF-β的另一个特征是， 可以促进更特异性靶向的是它通过GARP共价结合到特异性细胞表面。L-TGF-β 1 与整联蛋白TGF-β 8的结合是体内TGF-β活化所必需的。对于B2 V8激活机制，作为 和其他所有的一样，长期以来人们一直认为TGF-β必须从TGF-β中释放出来，这样游离的TGF-β才能 扩散并结合靶细胞上的受体。基于最近的结构数据， 电子冷冻显微镜（cryo-EM），我们最近提出了一个新的模型，其中Bpv β 8可以结合到L- TGF-β 1对呈递L-TGF-β 1/GARP复合物的细胞起作用，并诱导信号传导，而不释放和扩散TGF-β 1。 TGF-β 1。在这里，我们的三个目标，解决三个关键问题，关于这个新的模型L-TGF-β activation. (1)L-TGF-β 8/L-TGF-β 1/GARP三元复合物的L-TGF-β 1的哪些柔性结构域屏蔽TGF-β 1 从它的受体？(2)L-TGF-β 1与TGF-β 8结合诱导的柔性是介导TGF-β 1的必要条件吗 激活？(3)TGF-β受体（TGF-β R）与TGF-β 8/L-TGF-β 1/GARP复合物中的TGF-β 1结合吗？到 为了回答这些问题，我们将使用冷冻电镜来确定TGF β 8/L-TGF-β 1/GARP复合物的结构 以确定L-TGF-β的灵活性如何有助于TGF-β的激活，最后我们将捕获 TGF-β R与TGF-β 8/LTGF-β 1/GARP的多聚体复合物。这些研究将提高机械 了解TGF-β活化和抑制它的治疗靶向策略。

Summary/Abstract: TGF- drives the fibroinflammatory processes that leads to lung and airway fibrosis. The long-term goal of this project is to acquire a deep understanding of the regulation of TGF- activity to develop new strategies and treatments for fibrosing lung disease. There are few effective therapies to treat chronic fibrosing and inflammatory diseases of the lung. The cytokine TGF- is a central mediator of fibrosis and pathologic inflammation and is a potential therapeutic target in fibrosing lung disease. However, the practical utility of targeting TGF- itself or its receptors is limited by risk of toxicities seen in rodents, primates and humans. More specific methods to target the fibroinflammatory effects of TGF- are highly desirable. A promising method to more specifically target local effects of TGF- is to target its “activation” since it is always produced in a latent form (L-TGF-) that must be activated in order to function. Another feature of L-TGF- that could facilitate more specific targeting is that it is covalently bound to specific cell surfaces by GARP. L-TGF- binding to the integrin v8 is essential for TGF- activation in vivo. For the v8 activation mechanism, as well as all others, it has long been assumed that TGF- must be released from LAP so that free TGF- can diffuse and bind its receptors on target cells. Based on recent structural data obtained using single particle electron cryomicroscopy (cryo-EM), we have recently proposed a new model whereby v8 can bind to L- TGF- on cells presenting the L-TGF-/GARP complex and induce signaling without release and diffusion of TGF-. Here in three aims, we address three critical questions concerning this new model of L-TGF- activation. (1) Which flexible domains of L-TGF- of the v8/L-TGF-/GARP ternary complex shield TGF- from its receptors? (2) Is flexibility of L-TGF- induced by binding to v8 necessary to mediate TGF- activation? (3) Do TGF- receptors (TGF-Rs) bind to TGF- within the v8/L-TGF-/GARP complex? To answer these questions, we will use cryo-EM to determine the structure of the v8/L-TGF-/GARP complex to determine how flexibility of L-TGF- contributes to TGF- activation, and finally we will capture the multimeric complex of TGF-Rs with v8/LTGF-/GARP. These studies will improve mechanistic understanding of TGF- activation and therapeutic targeting strategies to inhibit it.