CacyBP/SIP对Wnt/β-catenin和MAPK/ERK信号网络的时空调控在抑制胃癌细胞增殖中的作用

CacyBP/SIP is a new target for S100 family proteins. Our previous study demonstrated that CacyBP/SIP inhibits growth and proliferation of gastric cancer cells. However, the underlying mechanisms retain unclear. It is found in our study that CacyBP/SIP, a component of ubiquitin ligase, not only promotes degradation for β-catenin, but also dephosphorylates and inactivates ERK1/2. More importantly, the spatiotemporal aspects of activity and subcellular localization for CacyBP/SIP are identified by our studies. Recent ?ndings provide tantalizing connections between Wnt/β-catenin and MAPK/ERK signal pathways which are regulated by activities and cellular distributions of signal molecules. So we speculate that CacyBP/SIP is a key molecule regulating synergistically Wnt/β-catenin and MAPK/ERK signal pathways by a spatiotemporal manner, and thereby inhibits cancer growth. In the present study, fluorescence imagings are used to observe spatiotemporal regulation of signaling by CacyBP/SIP and molecular biology techniques will be performed to identify the effect of CacyBP/SIP on signal cascade. This research will help to elucidate the regulatory mechanism of CacyBP/SIP through Wnt/β-catenin and MAPK/ERK signal pathways and might shed light on the pathogenic mechanisms of CacyBP/SIP in tumor development and progression.

CacyBP/SIP是S100蛋白的靶分子。我们证实：CacyBP抑制胃癌细胞生长、增殖；但其抑癌机制未完全阐明。我们研究及文献提示,CacyBP不仅促进胃癌细胞中β-catenin降解；且能使ERK1/2去磷酸化失活。更重要的是，CacyBP在胃癌细胞中具有活性和表达的时空差异。Wnt/β-catenin和MAPK/ERK通路之间存在"crosstalk"，且磷酸化修饰和细胞定位变化也是其重要的调控方式。由此推测,CacyBP可能是联系β-catenin及ERK信号网络的关键分子，通过对其活性及分布的动态时空调控，抑制肿瘤细胞增殖。本研究拟通过荧光成像技术，实时地在活细胞内研究CacyBP对通路分子时空动态的调控；采用基因突变等方法,探讨CacyBP不同功能状态对信号分子的影响，以期探明CacyBP对Wnt和MAPK通路的调控机制,为全面阐明CacyBP在抑制肿瘤生长中的作用奠定基础。

CacyBP/SIP是S100蛋白重要的靶分子，我们前期研究证实，CacyBP/SIP抑制胃癌和肾癌的生长、增殖，但是其机制尚未完全阐明。本课题通过荧光成像技术，研究CacyBP在胃癌细胞中时空动力学的变化；采用质谱分析、免疫沉淀等方法，研究CacyBP/SIP对MAPK/ERK信号通路的调控在胃癌细胞增殖中的作用；通过泛素降解实验、放线菌酮（CHX）蛋白合成抑制实验，研究CacyBP/SIP对Wnt/β-catenin通路的时空调控 。研究结果显示，CacyBP/SIP 在胃癌细胞内具有亚细胞定位的变化，并受到Ca2+离子浓度、PKC活性、细胞密度及细胞周期等因素的调控； CacyBP/SIP能抑制胃癌细胞中ERK的磷酸化，而ERK信号的激活可减弱CacyBP/SIP的抑癌作用，提示ERK途径可能介导了CacyBP/SIP的抑癌作用，但CacyBP/SIP 与ERK通路信号分子之间并没有直接的相互作用；CacyBP/SIP能结合β-catenin，泛素化降解磷酸化以及非磷酸化的β-catenin，这种调节具有时空调控特性；CacyBP/SIP 能与Rab11结合，并可能通过外泌体发挥肿瘤抑制作用。本课题的研究为全面阐明CacyBP/SIP功能及肿瘤异常增殖的机制奠定理论基础。