Protein Kinase Signaling and Cell Cycle Control

描述（由申请人提供）：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/苏氨酸结合结构域如何调节细胞周期进程和对DNA损伤的反应。在对遗传毒性应激的反应中，细胞激活两个典型的蛋白激酶途径，ATR-Chk 1途径和ATM-Chk 2途径。我们最近发现了由p38 MAPK和MAPKAP激酶2（MK2）介导的第三种DNA损伤反应途径，这是p53缺陷型肿瘤细胞在DNA损伤后生存所必需的。重要的是，这种途径在具有完整p53功能的细胞中很大程度上被抑制，使其成为特异性削弱癌细胞中DNA损伤反应的理想靶点。此外，与专门响应来自DNA损伤本身的信号的ATR-Chk 1和ATM-Chk 2途径不同，p38 MAPK-MK2途径是一种更全面的应激反应途径，其也可以被其他类型的细胞应激激活，并且在炎症和肿瘤发生期间的细胞因子产生中起关键作用。我们相信p38 MAPK-MK2途径通过整合肿瘤细胞内的DNA损伤反应途径与邻近肿瘤微环境中的炎症和细胞因子信号传导，在致癌和遗传毒性应激期间发挥特别新颖的作用。 在这项提案中，我们定义了MK2在肿瘤发展和治疗反应中的作用，使用新的条件性基因敲除小鼠模型，确定MK2调节G1/S检查点的分子机制，并通过RNA结合蛋白的磷酸化定义其在转录后基因表达调控中的作用，然后我们通过结构和机制方法进行探索。最后，我们确定了新的MK2，Chk 1和Chk 2底物参与细胞周期控制和DNA损伤反应。从所提出的实验中出现的数据应该（1）大大增强我们对肿瘤和基质衍生的MK2在癌症发展和进展中的作用的理解，（2）扩展我们对控制癌症环境风险的信号传导途径的知识，和（3）鉴定和验证可以设计癌症预防策略和抗癌疗法的新分子靶点，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.