整合素与丝氨酸蛋白酶协同作用介导TGF-β2前体的激活

转化生长因子(TGF)-β调节多种关键生理功能，其信号通路失调与癌症、纤维化等重大疾病密切相关。近年来TGF-β研究领域的热点转向了其信号通路的上游，即TGF-β前体的特异性激活。TGF-β三种亚型1、2、3均以非活性前体形式合成、分泌并储存于胞外，前体的不同激活机制是三者发挥不同功能的关键。前期预实验结果表明，TGF-β2前体的激活需要整合素与丝氨酸蛋白酶协同介导。为进一步阐明其分子机制，我们将运用生化、细胞生物学与结构学手段，鉴定参与TGF-β2前体激活的整合素与丝氨酸蛋白酶种类，揭示两者作用机制，解析TGF-β2前体结构，并探明其在激活过程中结构的变化，结合功能与结构研究系统阐明整合素与丝氨酸蛋白酶协同介导TGF-β2前体激活的分子机制。本项目将有力地推动TGF-β上游调控这一前沿研究领域的拓展与深入；并为针对不同TGF-β亚型，发展更特异更安全的新型治疗方法提供理论依据和具体靶点。

Transforming growth factor (TGF)-βs are potent and versatile cytokines. They play pivotal roles in growth, development, wound healing, homeostasis and immune regulation. Dysregulation of the TGF-β pathway leads to serious diseases including cancer, fibrosis and cardiovascular diseases. In recent years, the focus of the TGF-β field has shifted to the upstream of the TGF-β signaling pathway, i.e., the activation of the latent TGF-β precursor (pro-TGF-β). Three TGF-β isoforms TGF-β1,2&3 are all synthesized, secreted, and stored in the extracellular environments as pro-TGF-βs, different activation mechanisms of the pro-TGF-βs are key to how the three isoforms carry out distinct physiological functions. Our experimental findings suggest that both integrin binding and serine protease cleavage are necessary for pro-TGF-β2 activation. We thus hypothesize that integrin and serine protease cooperatively activate pro-TGF-β2. To elucidate the mechanism of cooperative activation by integrin and serine protease, we will utilize a wide range of research strategies including biochemistry, cell biology, and structural biology methods. We will identify the type (or types) of integrin and serine protease that are involved in pro-TGF-β2 activation, investigate how integrin and serine protease interact with and activate pro-TGF-β2, solve the high-resolution structure of pro-TGF-β2, and illustrate the conformational changes in pro-TGF-β2 induced by integrin binding and the subsequent proteolytic cleavage. The proposed work will deepen our understanding in the complex and yet delicate extracellular activity regulation mechanisms of the TGF-β family. This work will also provide new insights in the development of a new TGF-β targeted therapy, i.e., targeting different isoforms of TGF-βs.