Protein Kinase Signaling and Cell Cycle Control

描述(申请人提供)：我们实验室的长期目标是了解特定的蛋白激酶信号通路和磷酸丝氨酸/苏氨酸结合域如何调节细胞周期进程和对DNA损伤的反应。作为对基因毒性应激的响应，细胞激活了两条典型的蛋白激酶通路：ATR-Chk1通路和ATM-Chk2通路。我们最近发现了由p38MAPK和MAPKAP Kinase-2(MK2)介导的第三条DNA损伤反应通路，该通路对于p53缺陷肿瘤细胞在DNA损伤后存活是绝对必要的。重要的是，在p53功能完整的细胞中，这一途径在很大程度上是可有可无的，使其成为专门损害癌细胞DNA损伤反应的理想靶点。此外，与ATR-Chk1和ATM-Chk2信号通路不同，p38MAPK-MK2通路是一个更具全局性的应激反应通路，也可以被其他类型的细胞应激激活，并在炎症和肿瘤发生过程中发挥关键作用。因此，我们认为p38MAPK-MK2通路通过整合肿瘤细胞内的DNA损伤反应通路和邻近肿瘤微环境中的炎症和细胞因子信号，在致癌和遗传毒性应激过程中发挥着特别新的作用。在这个方案中，我们使用新的条件性基因敲除小鼠模型来定义MK2在肿瘤发展和治疗反应中的作用，确定MK2调节G1/S检查点的分子机制，并通过核糖核酸结合蛋白的磷酸化来确定其在转录后调控基因表达中的作用，然后我们通过结构和机制的方法来探讨这一点。最后，我们确定了参与细胞周期控制和DNA损伤反应的新的MK2、Chk1和Chk2底物。拟议的实验数据将：(1)大大加强我们对肿瘤和间质来源的MK2在癌症发生和发展中作用的理解，(2)扩大我们对控制癌症环境风险的信号通路的知识，以及(3)确定和验证新的分子靶点，针对这些分子靶点设计癌症预防策略和抗癌治疗，包括MK2本身和RNA结合蛋白。

DESCRIPTION (provided by applicant): The long-term goal of our laboratory is to understand how specific protein kinase signaling pathways and phosphoserine/threonine-binding domains regulate cell cycle progression and the response to DNA damage. In response to genotoxic stress, cells activate two canonical protein kinase pathways, the ATR-Chk1 pathway, and the ATM-Chk2 pathway. We recently identified a third DNA damage response pathway mediated by p38MAPK and MAPKAP Kinase-2 (MK2) that is absolutely essential for p53-defective tumor cells to survive after DNA damage. Importantly, this pathway is largely dispensable in cells with intact p53 function, making it an ideal target for specifically impairing the DNA damage response in cancer cells. Furthermore, unlike the ATR-Chk1 and ATM-Chk2 pathways that are dedicated to responding solely to signals from DNA damage per se, the p38 MAPK-MK2 pathway is a much more global stress-response pathway that can also be activated by other types of cellular stress, and plays a critical role in cytokine production during inflammation and tumorigenesis Thus, we believe that the p38MAPK-MK2 pathway plays a particularly novel role during oncogenic and genotoxic stress by integrating DNA damage response pathways within tumor cells with inflammation and cytokine signaling in the adjacent tumor microenvironment. In this proposal we define the role of MK2 in both tumor development and therapeutic response using novel conditional knock-out mouse models, identify the molecular mechanism by which MK2 regulates the G1/S checkpoint, and define its role in post-transcriptional regulation of gene expression through phosphorylation of RNA-binding proteins, which we then explore through a structural and mechanistic approach. Finally, we identify new MK2, Chk1 and Chk2 substrates involved in cell cycle control and DNA damage responses. Data emerging from the proposed experiments should (1) substantially enhance our understanding of the roles of tumor- and stromal derived MK2 in cancer development and progression, (2) expand our knowledge of signaling pathways that control environmental risk for cancer, and (3) identify and validate new molecular targets against which both cancer prevention strategies and anti-cancer therapies can be designed, including MK2 itself and RNA-binding proteins.