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 GTf 3与其调节蛋白（特别是Dbl家族鸟嘌呤核苷酸交换因子（GEF））之间相互作用的机理见解应用于设计靶向人类疾病（如癌症）中失调的Rac活性的新方法。GEF-Rac信号传导轴位于由生长因子、细胞因子、应激和粘附分子引发的许多信号传导事件的十字路口。它们的功能相互作用导致Rac的激活和多种Rac介导的生理反应，包括肌动蛋白和微管细胞骨架重组、粘附、迁移和增殖。在上一个资助期内，我们研究了Rac 1与GEFs和效应子相互作用的结构-功能关系，并成功地推导出涉及Rac 1的几种功能相互作用的结构和动力学信息。此外，我们已经研究了Rac 1的作用，在小鼠中的条件基因靶向方法，揭示了Rac 1的几个细胞功能，不能被发现通过常规手段。最后，我们发现了第一代小分子抑制剂NSC 23766，其在体外和体内有效靶向Rac，并利用其研究了Rac GTP酶的许多生理和病理功能，从造血干细胞动员、血小板调节到神经鞘瘤表型逆转。在该提案中，我们将（1）通过基于新解析的Rac 1-NSC 23766晶体结构的筛选和药物化学，寻求基于结构-功能的Rac靶向小分子抑制剂的合理设计和改进，以及（2）将Rac靶向小分子抑制剂应用于慢性髓性白血病小鼠模型中白血病干细胞从骨髓小生境的动员。这些基于机制的小分子抑制剂设计研究和在新的病理学背景下的临床前验证不仅将为癌症研究中的广泛用途提供改进的Rac GT3抑制剂一代，而且还将涉及从其微环境中动员白血病干细胞的创新应用途径，其可用作有效根除癌症的组合疗法中的重要方案。

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.