alphaVbeta1 integrin: Analyzing the hidden master of fibrosis

在我们的生活中，我们都依赖于有效的伤口愈合。然而，伤疤依然存在。虽然疤痕的形成对完全愈合伤口很重要，但它会导致组织功能丧失。例如，疤痕组织在梗塞后愈合心脏，但疤痕组织不跳动，疤痕皮肤上没有毛发生长，并且肺中的疤痕不有助于气体交换。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并导致器官衰竭。这种致病性进展称为纤维化。发达国家40%以上的死亡归因于纤维化。肥胖是纤维化的另一个危险因素。随着肥胖人数的增加，纤维化相关死亡人数可能会在未来几年内增加。传统上，纤维化对每个器官都有不同的命名，掩盖了它在所有组织中共有的共同特征。在纤维化开始时，细胞转化为肌成纤维细胞，肌成纤维细胞分泌增加量的细胞外基质（ECM）蛋白，其闭合伤口并最终形成疤痕。这种转化的主要调节因子是转化生长因子β（TGF β）细胞因子。TGF β作为无活性的LAP-TGF β复合物存在于ECM中。整合素（重要的细胞-基质粘附受体）与复合物的结合释放TGF β。在过去，α V-整联蛋白被认为与该过程相关。然而，最近的研究表明，只有α V β 1整联蛋白负责TGF β在生理环境中的释放。不幸的是，由于技术上的挑战，研究界迄今为止很少对α V β 1进行分析。整联蛋白异二聚体的两个部分都与许多其他亚基结合，从而掩盖了其他整联蛋白群中的α V β 1。在这里，我将建立alphaV β 1特异性底物，通过“将这种整合素从人群中剔除”来解决这个问题。具体来说，我将分析alphaV β 1产生二元选择底物的配体偏好。有了这项技术，最近建立在我的博士学位，alphaV β 1将物理上从其他整合素分离，由于他们的差异配体亲和力。通过这种方法，alphaV β 1将可用于各种显微镜和生理技术，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能够在细胞环境中研究alphaV β 1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基底功能化的结合将产生一个适合于任何细胞粘附受体的分析平台。通过实现这些目标，我将同时提高对α V β 1和纤维化的理解。这将为药物干扰纤维化的主要调节因子提供多种新的可能性。

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.