葡萄糖依赖性促胰岛素释放肽受体GIPR信号复合物结构及其在2型糖尿病中的分子机制研究

葡萄糖依赖性促胰岛素释放肽受体GIPR是重要的2型糖尿病药物靶标，目前GIPR作用于2型糖尿病的发病机制尚不清楚，极大限制了治疗2型糖尿病的GIPR新配体药物的发现。我们已经证实GIPR激活是通过激活异源三聚体Gs信号通路，凭借解析PTH1R、CRF1R和CRF2R与Gs信号复合物高分辨率结构方面的丰富经验，初步获得该复合物，本项目拟通过单颗粒冷冻电镜技术与生化、细胞功能相结合的手段研究GIPR-Gs复合物结构和信号传导机制，发展新的复合物表达稳定方法，克服组装稳定的GIP-GIPR-Gs复合物的技术瓶颈，解析激活状态的GIPR-Gs复合物的高分辨结构（<3.0Å），以揭示其激活状态下的动力学分子作用机制，探讨GIPR-Gs信号复合物在2型糖尿病发病和治疗中的分子作用机制，为靶向GIPR的抗2型糖尿病药物设计提供最直接可靠的受体激活模型和结构基础，推进小分子药物的研发，具有广泛的应用前景。

Glucose-dependent insulinotropic peptide receptor (GIPR) is an important drug target for type 2 diabetes mellitus. The mechanism of the effect of GIPR on type 2 diabetes remains unclear, which greatly limits the discovery of new ligands of GIPR for the treatment of type 2 diabetes. We have confirmed that activation of GIPR transduces extracellular GIP signal into an intracellular signal by activating the heterotrimeric Gαs protein, We have rich experience in determining high resolution structures of several class B GPCR-Gs complexes, including PTH1R-Gs, CRF1R-Gs and CRF2R-Gs complexes. In this project, we are aimed toward structural and functional studies of the GIP-GIPR-Gs complex. In the preliminary studies, we have obtained the initial GIP bound GIPR-Gs complex. We will combine single-particle cryo-EM, biochemical and cell-based functional experiments to study the structure and signaling mechanism of the of GIPR-Gs complex. We will develop novel methods of protein expression and complex stabilization to overcome the technical barriers for the assembly of a stable GIP-GIPR-Gs complex, with an ultimate goal of obtaining a high resolution (<3.0 Å) structure of the GIP-GIPR-Gs complex. The results from this project will provide a molecular framework to understand the structure and dynamics of ligand binding and activation of GIPR, which helps to explain the mechanism of action for the role of GIPR in type 2 diabetes. This project will provide the most direct molecular basis of peptide hormone recognition, receptor activation, Gs protein coupling for GIPR, and structural basis of drug design, including small molecule agonists, targeting GIPR for the treatment of type 2 diabetes.