Conformational regulation of TGF-β activation by integrin αvβ6

摘要/摘要：转化生长因子-β是肺纤维化的关键驱动因素。我们研究的长期目标是获得一个 深入了解转化生长因子-β的活性调节以开发治疗纤维化的新策略和新疗法 肺部疾病。目前，还没有治疗肺纤维化的有效方法。多功能细胞因子转化生长因子-1 B是一种有效的纤维化介质，是治疗纤维化肺疾病的潜在靶点。然而， 靶向转化生长因子-b本身或其受体与已证实的风险有关，这一点从 啮齿动物、灵长类动物和人类。更有选择性地靶向转化生长因子-b的纤维炎症效应，而不是 扰乱其正常的基本功能是非常可取的。转化生长因子-b的一个特性可能允许更多 选择性靶向是靶向它的“激活”，因为它总是以潜伏的形式(L-转化生长因子-β)产生，需要 为了发挥作用而激活。L-转化生长因子-b另一个可以更具针对性的特征是 它通常通过与转化生长因子-b结合而共价结合到细胞外基质或细胞表面。 结合蛋白，如潜伏的转化生长因子-b结合蛋白(LTBP)或糖蛋白-A重复 (GARP)。我们和其他人已经证明L-转化生长因子-b与两个整合素，a8和a结合 VB VB 6对以下各项至关重要 转化生长因子-β在体内的激活。对于整合素α6的激活机制，长期以来一直被认为是转化生长因子-β VB 必须从LAP中释放，以便游离的转化生长因子-b能够扩散并将其受体结合到靶细胞上。结构性的 这种释放转化生长因子-β的机制还不完全清楚，因为 VB 6还没有研究过 在与转化生长因子-β结合的复合体中结合转化生长因子-β结合蛋白。基于最近使用单一数据获取的结构数据 粒子电子冷冻显微镜(CRYO-EM)，我们最近提出了一种新的模型， VB 8可以绑定 作用于呈现L-转化生长因子-β/GARP复合体的细胞上的L-转化生长因子-β，诱导信号不释放和扩散 转化生长因子-β的表达。这两种不同的转化生长因子-b激活模型可能能够单独靶向，这可能 帮助降低治疗风险。在这里的四个目标中，我们将使用基于结构的方法来解决 A的作用机制 VB 6-介导的转化生长因子-β激活。我们将使用电子冷冻显微镜技术(低温显微镜)。 EM)，这是一种允许蛋白质和蛋白质复合体的高分辨率结构的技术 生理上相关的条件。冷冻-EM将用于研究整合素a的作用 VB 6构象在 转化生长因子-β的激活机制。这些研究将提高对转化生长因子-b激活的机制的理解。 以及治疗靶向策略，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.