RalA通过小窝蛋白-1调节肿瘤细胞活性氧自由基和三磷酸腺苷的生成

目的 通过研究RalA和Cav-1对癌细胞线粒体功能以及活性氧自由基（reactive oxygen species, ROS）和三磷酸腺苷(adenosine triphosphate, ATP)生成的影响，探讨RalA在癌细胞能量代谢中所起的调节作用，且此作用可能通过影响Cav-1及小窝的运动性得以实现。方法 首先使用siRNA抑制MDA-MB-231乳腺癌细胞株的RalA和Cav-1表达水平，然后采用蛋白免疫印迹、共聚焦显微镜、荧光定量技术比较抑制前后细胞线粒体膜电位的变化以及ROS、ATP和糖酵解产物乳酸盐生成的改变。结果 （1） RalA和Cav-1表达量降低直接引起线粒体膜电位的大幅下降。（2） RalA和Cav-1的表达抑制导致ATP生成降低而H2O2的水平升高，结合线粒体膜电位降低的结果，观察到线粒体功能的紊乱。（3） 伴随线粒体功能的明显抑制，RalA和Cav-1表达量降低的细胞中检测到了大量的糖酵解产物乳酸盐。结论 RalA和Cav-1通过抑制线粒体功能，提高糖酵解水平，共同调节细胞的能量代谢转换。RalA的调节作用通过Cav-1得以实现，并且这种调节作用可能与小窝的内吞及运动性有关。研究结果丰富了癌症能量代谢的研究，为靶向癌症能量代谢紊乱的治疗方法提供了新的切入点。
Objective By analyzing mitochondrial function, reactive oxygen species (ROS) and adenosine triphosphate (ATP) production under different levels of RalA and caveolin-1 (Cav-1) expression, to investigate the regulation role of RalA played in cancer metabolism and explore the possibility of its regulation role involved in Cav-1 and caveolae motility. Methods Firstly, RalA and Cav-1 expression were inhibited by siRNA in breast cancer cell line MDA-MB-231, and then the changes of mitochondrial membrane potential (MMP), ROS production, ATP generation and L-lactate level before and after inhibition were assessed by Western blotting, confocal microscope and fluorescence quantification. Results (1) The decreased RalA and Cav-1 expression led to a significant reduction of MMP directly. (2) Low RalA and Cav-1 expression resulted in an inhibition of ATP production and an increase of H2O2 generation. With the reduction of MMP, mitochondrial malfunction was observed. (3) With mitochondrial function suppression, an elevated level of glycolysis metabolite L-lactate was also detected in RalA and Cav-1 deprived cells. Conclusions RalA and Cav-1 mediate cellular metabolic switch by inhibiting mitochondrial function and simultaneously boosting glycolysis. This regulation role of RalA depends on its association with Cav-1, and possibly is related to the endocytosis and motility of caveolae. The research findings enrich the cancer metabolic studies, and provide a novel approach for cancer therapeutic strategy targeted to cellular metabolism.