Conformational regulation of TGF-β activation by integrin αvβ6

摘要：TGF-b是肺纤维化的关键驱动因素。我们研究的长期目标是获得 深入了解TGF-β活性的调节，以开发新的纤维化策略和治疗方法 肺病。目前，没有有效的治疗肺纤维化的疗法。多功能细胞因子TGF- B是一种有效的纤维化介质，是纤维化肺病的潜在治疗靶点。然而，在这方面， 靶向TGF-b本身或其受体与已证实的风险相关， 啮齿类、灵长类和人类。更有选择性地靶向TGF-β的纤维炎性作用， 干扰其正常的基本功能是非常需要的。TGF-β的一个特性可能允许更多的 选择性靶向是靶向其“活化”，因为它总是以需要的潜伏形式（L-TGF-B）产生 激活，以发挥作用。L-TGF-B的另一个可以促进更特异性靶向的特征是， 它通常通过与TGF-β结合而共价结合于细胞外基质或细胞表面 结合蛋白如潜伏-TGF-B结合蛋白（LTBP）或糖蛋白-A重复占优势 （GARP）。我们和其他人已经表明，L-TGF-B与两种整合素α 8和α 10结合， VB VB 六是必不可少的 体内TGF-β活化。对于整合素α 6的激活机制，长期以来一直认为TGF-β VB 必须从细胞膜中释放出来，这样游离的TGF-β才能扩散并结合靶细胞上的受体。结构性 这种TGF-β释放的机制还不完全清楚， VB 6尚未研究 与结合于TGF-β结合蛋白的TGF-β复合。根据最近的结构数据， 粒子电子低温显微镜（cryo-EM），我们最近提出了一个新的模型， VB 8可以绑定 与呈递L-TGF-B/GARP复合物的细胞上的L-TGF-B结合，并诱导信号传导而不释放和扩散 TGF-β这两种不同的TGF-β激活模型可能能够分别靶向，这可以 有助于降低治疗风险。在这四个目标中，我们将采用基于结构的方法来解决 机理 VB 6-介导的TGF-β活化。我们将使用电子低温显微镜技术（cryo- EM），这是一种允许在细胞中蛋白质和蛋白质复合物的高分辨率结构的技术。 生理相关条件。Cryo-EM将用于检查整合素a的作用。 VB 6构象 TGF-β激活的机制。这些研究将提高对TGF-β激活机制的理解 和治疗靶向策略，以更有选择性和安全地抑制它。

Summary/Abstract: TGF-b is a key driver of lung fibrosis. The long-term goal of our research is to acquire a deep understanding of the regulation of TGF-b activity to develop new strategies and treatments for fibrosing lung disease. Currently, there are no effective therapies to treat lung fibrosis. The multifunctional cytokine TGF- b is a potent mediator of fibrosis and is a potential therapeutic target in fibrosing lung disease. However, targeting TGF-b itself or its receptors is associated with demonstrated risks as evidenced by toxicities in rodents, primates and humans. More selective targeting of the fibroinflammatory effects of TGF-b, without perturbing its normal essential functions are highly desirable. One property of TGF-b that may allow more selective targeting is to target its “activation” since it is always produced in a latent form (L-TGF-b) that requires activation in order to function. Another feature of L-TGF-b that could facilitate more specific targeting is to that it is normally covalently bound to the extracellular matrix or to the surface of cells by association with TGF-b binding proteins such as latent-TGF-b binding protein (LTBP) or glycoprotein-A repetitions predominant (GARP). We and others have shown that L-TGF-b binding to two integrins, a 8 and a vb vb 6 is essential for TGF-b activation in vivo. For the integrin a 6 activation mechanism, it has long been assumed that TGF-b vb must be released from LAP so that free TGF-b can diffuse and bind its receptors on target cells. The structural mechanism for such release of TGF-b is incompletely understood since full-length a vb 6 has not been studied in complex with TGF-b bound to TGF-b binding proteins. Based on recent structural data obtained using single particle electron cryomicroscopy (cryo-EM), we have recently proposed a new model whereby a vb 8 can bind to L-TGF-b on cells presenting the L-TGF-b/GARP complex and induce signaling without release and diffusion of TGF-b. These two different models of TGF-b activation may be able to be separately targeted, which could help mitigate therapeutic risk. Here in four aims, we will employ a structure-based approach to address the mechanism of a vb 6-mediated TGF-b activation. We will use the technique of electron cryomicroscopy (cryo- EM), which is a technique that allows for high-resolution structures of proteins and protein complexes in physiologically relevant conditions. Cryo-EM will be used to examine the role of integrin a vb 6 conformation in the mechanism of TGF-b activation. These studies will improve mechanistic understanding of TGF-b activation and therapeutic targeting strategies to more selectively and safely inhibit it.