Rac GTPase-Specific Small Molecular Inhibitors

描述(由申请人提供)：该项目的长期目标是将Rho家族的RAC GTP酶与其调节蛋白，特别是DBL家族鸟嘌呤核苷酸交换因子(GEF)之间相互作用的机制洞察力应用于设计针对人类疾病(如癌症)中放松调控的RAC活性的新方法。全球环境基金-RAC信号轴位于许多信号事件的十字路口，这些信号事件由生长因子、细胞因子、压力和黏附分子启动。它们的功能相互作用导致RAC的激活和RAC介导的一系列生理反应，包括肌动蛋白和微管细胞骨架的重组、黏附、迁移和增殖。在过去的资助期间，我们研究了rac1与GEF和效应器的相互作用的结构-功能关系，并成功地获得了涉及rac1的几种功能相互作用的结构和动力学信息。此外，我们通过条件基因打靶方法在小鼠身上研究了rac1的作用，以揭示传统方法无法发现的rac1的几个细胞功能。最后，我们发现了第一代小分子抑制剂NSC23766，它在体外和体内都能有效地靶向RAC，并利用它来研究RAC GTP酶的一系列生理和病理功能，从造血干细胞动员、血小板调节到神经鞘瘤表型逆转。在这项建议中，我们将(1)通过筛选和药物化学，基于新拆分的rac1-NSC23766晶体结构，进行基于结构和功能的合理设计和改进RAC靶向小分子抑制剂，以及(2)将RAC靶向小分子抑制剂应用于慢性粒细胞白血病小鼠模型的骨髓干细胞动员。这些基于机制的小分子抑制剂设计和临床前验证研究不仅将为癌症研究提供新一代的RAC GTP酶抑制剂，并将为从微环境中动员白血病干细胞开辟一条创新的应用途径，可作为有效根除癌症的联合治疗的重要方案。公共卫生相关性：根据最近的研究，RAC GTP酶已成为潜在的抗癌治疗靶点。这项拟议的工作将通过转化从长达十年的RAC GTP酶用于抗癌治疗的生化、结构、细胞生物学和动物研究中获得的机制信息，进行基于结构的RAC GTP酶新化学抑制剂的设计。此外，拟议的工作将有助于建立一种新的治疗概念，即在白血病干细胞中靶向RAC可以导致它们从利基中动员。我们的研究将为未来癌症研究中的联合治疗提供新的可能性。

DESCRIPTION (provided by applicant): The long-term objective of this project is to apply the mechanistic insights of the interaction between Rac GTPase of the Rho family and their regulatory proteins, the Dbl family guanine nucleotide exchange factors (GEFs) in particular, to the design of novel approaches to target deregulated Rac activities in human diseases such as cancer. The GEF-Rac signaling axis lies in the crossroads of many signaling events initiated by growth factors, cytokines, stress, and adhesion molecules. Their functional interaction leads to the activation of Rac and a variety of Rac-mediated physiological responses including actin and microtubule cytoskeletal reorganization, adhesion, migration, and proliferation. In the last funding period, we have studied the structure-function relationship of Rac1 in regard of its interaction with GEFs and effectors, and have succeeded in deriving structural and kinetic information of several functional interactions involving Rac1. Further, we have studied the role of Rac1 by a conditional gene targeting approach in mice to reveal several cell functions of Rac1 that could not have been discovered by conventional means. Last, we have discovered a first generation small molecule inhibitor, NSC23766, that is effective in targeting Rac in vitro and in vivo, and have utilized it to study a number of physiological and pathological functions of Rac GTPases ranging from hematopoietic stem cell mobilization, platelet regulation, to schwannoma phenotype reversion. In this proposal, we will (1) pursue structure-function based rational design and improvement of Rac-targeting small molecule inhibitors by screening and medicinal chemistry based on the newly resolved Rac1-NSC23766 crystal structure, and (2) apply the Rac-targeting small molecule inhibitors to leukemia stem cell mobilization from their bone marrow niche in a chronical myeloid leukemia mouse model. These mechanism-based studies of small molecule inhibitor design and pre-clinical validation in a novel pathologic context will not only provide an improved generation of Rac GTPase inhibitors for a wide range of usage in cancer research, but also will implicate an innovative avenue of application in mobilizing leukemia stem cells from their microenvironment, which can be utilized as an important regiment in combinatory therapy for effective eradication of cancer. PUBLIC HEALTH RELEVANCE: Rac GTPases have emerged as potential anti-cancer therapeutic targets by recent studies. The proposed work will pursue structure-based design of new chemical inhibitors of Rac GTPases by translating the mechanistic information obtained from the decade-long biochemical, structural, cell biological, and animal studies of Rac GTPases for anti-cancer therapy. Further, the proposed work will help establish a novel therapeutic concept that targeting Rac in leukemia stem cells could result in their mobilization from the niche. Our studies will raise a new possibility for future combinatory therapy in cancer research.