alphaVbeta1 integrin: Analyzing the hidden master of fibrosis

我们一生都依赖于有效的伤口愈合。然而，伤疤依然存在。虽然疤痕的形成对伤口的完全愈合很重要，但它的代价是组织功能的丧失。例如，疤痕组织可以在心肌梗塞后治愈心脏，但是疤痕组织不会跳动，疤痕皮肤上不会长出毛发，肺部的疤痕也不能促进气体交换。如果疤痕的大小超过一定的大小，它会干扰正常的器官功能，导致器官衰竭。这种致病过程称为纤维化。在发达国家，超过40%的死亡是由纤维化造成的。肥胖是纤维化的另一个危险因素。随着肥胖人数的增加，未来几年与纤维化相关的死亡人数可能会增加。传统上，纤维化对每个器官的命名不同，掩盖了它在所有组织中的共同特征。在纤维化发生时，细胞转化为肌成纤维细胞，分泌更多的细胞外基质（ECM）蛋白，使伤口愈合并最终形成疤痕。这种转化的主要调节因子是转化生长因子β (tgfβ)细胞因子。tgf - β以非活性lap - tgf - β复合物的形式存在于ECM中。整合素（重要的细胞基质粘附受体）与复合物结合释放tgf β。过去，人们认为alphav整合素与这一过程有关。然而，最近的研究表明，在生理环境中，只有alphaVbeta1整合素负责tgf - β的释放。不幸的是，由于技术上的挑战，alphaVbeta1到目前为止很少被研究界分析。整合素异源二聚体的两个部分都与许多其他亚基结合，从而掩盖了其他整合素群中的alphaVbeta1。在这里，我将建立alphavbeta1特异性底物，通过“从人群中取出这个整合素”来解决这个问题。具体来说，我将分析alphaVbeta1的配体偏好，以产生二元选择底物。利用我博士期间最近建立的这项技术，alphaVbeta1将由于其不同的配体亲和力而与其他整合素物理分离。通过这种方法，alphaVbeta1将可用于各种显微和生理技术，允许其深入表征。使用这些具有单粒子跟踪的二元选择底物将使我具有独特的能力来研究细胞环境中alphaVbeta1的动力学和构象特异性调节。此外，这种先进的显微镜和独特的底物功能化的结合将产生一个分析平台，适用于任何细胞粘附受体。通过达到这些目标，我将在加深对alphaVbeta1和纤维化的认识的同时。这将为这种纤维化的主要调节因子提供多种新的药理干扰可能性。

We are all depending on efficient wound healing throughout our live. However, a scar remains. While the formation of a scar is important to fully heal wounds, it comes at the prize of lost tissue functionality. For example, scar tissue heals the heart after an infarct, but the scar tissue does not beat, no hair grows on scarred skin, and scars in a lung do not contribute to gas exchange. If the size of the scar exceeds a certain size, it interferes with proper organ function and leads to organ failure. Such a pathogenic progression is called fibrosis. Fibrosis is attributed to more than 40% of all death in the developed world. Obesity is an additional risk factor for fibrosis. With increasing number of obese people it is likely that the number of fibrosis-associated deaths will increase during the next years. Traditionally, fibrosis is named differently for every organ, masking the common features it shares in all tissues. At the onset of fibrosis is the transformation of cells into myofibroblasts that secrete increased amounts of extracellular matrix (ECM) proteins that close the wound and eventually form the scar. The master regulator of this transformation are transforming growth factor beta (TGFbeta) cytokines. TGFbeta is present in the ECM as an inactive LAP-TGFbeta complex. Binding of integrins, important cell-matrix adhesion receptors, to the complex releases TGFbeta. In the past, alphaV-integrins were assumed to be relevant in this process. Recent work suggests, however, that only alphaVbeta1 integrin is responsible for TGFbeta release in physiological settings. Unfortunately, alphaVbeta1 was so far rarely analysed by the research community because of technical challenges. Both parts of the integrin heterodimer associate with many other subunits thereby masking the alphaVbeta1 in the crowd of other integrins. Here, I will establish alphaVbeta1-specific substrates to address this problem by “taking this integrin out of the crowd”. Specifically, I will analyze the ligand preference of alphaVbeta1 to produce binary choice substrates. With this technique, recently established during my PhD, alphaVbeta1 will be physically separated from other integrins due to their differential ligand affinities. By this approach, alphaVbeta1 will be made available for various microscopic and physiological techniques, allowing its in-depth characterization. Using these binary choice substrates with single-particle tracking will give me the unique ability to study dynamics and conformation-specific regulation of alphaVbeta1 in a cellular setting. Moreover, this combination of advanced microscopy and unique substrate functionalization will yield an analysis platform that is suitable for any cell adhesion receptors. By reaching these goals, I will improve the understanding at the same time of alphaVbeta1 and fibrosis. This will offer multiple new possibilities for pharmacological interference with this master regulator of fibrosis.