丝氨酸代谢酶PSPH通过结合周期蛋白影响肿瘤发展的机制研究

Tumor metabolism research is no longer limited to Warburg Effect, and nowadays study of non-metabolic functions of metabolic enzymes is becoming more and more prevalent and attracts extensive attention because of its significance for cancer therapy. Our previous discovery showed that activated serine synthesis pathway is critical for cancer cell survival under nutrient stressed conditions, but it is interesting to note that addition of exogenous serine cannot rescue the defect of cell proliferation and abnormal cell cycle upon PSPH knockdown. Unpublished data revealed that PSPH interacts with protein kinase Aurora A which is vital for cell cycle progression based on IP-MS screening and Co-IP validation, thus we hypothesize that PSPH promotes cancer progression through Aurora A mediated cell cycle dysregulation which is not dependent on metabolism variation. Then we will analyze the interaction fragments and amino acid sites between PSPH and Aurora A, monitor the regulation of PSPH on the events of cell mitosis, and finally validate the relationship between PSPH and Aurora A in tumor formation through xenograft and cancer induced mouse models together with clinical specimens at molecular, cellular and animal level, respectively. Ultimately, we want to provide new evidence and prevention targets for cancer therapy through illuminating the novel functions of PSPH and deciphering the orchestration between metabolism reprogramming and abnormal cell cycle progression in tumor development.

目前人们对肿瘤代谢的研究已经超出经典Warburg Effect的范畴，代谢酶的非代谢功能的解析已逐渐成为本领域的研究热点之一。我们前期发现丝氨酸代谢通路的激活对于压力条件下细胞的存活至关重要。但有趣的是外源添加丝氨酸并不能回复丝氨酸合成酶 PSPH缺失带来的增殖缺陷和周期紊乱(Cell Research, 2015)。在尚未发表的数据中，我们通过质谱筛选及Co-IP验证，发现PSPH结合周期蛋白Aurora A。因此，我们提出PSPH通过结合Aurora A影响周期进程促进肿瘤发展的假说。我们将在分子、细胞、动物水平解析PSPH和Aurora A结合的片段和作用位点，检测PSPH对细胞分裂过程中重要事件的调节，验证二者结合在动物成瘤和临床样本中的关系。本项目将通过研究PSPH促进肿瘤发生发展的新机制和新功能，阐述代谢酶调节周期异常的重要意义，为肿瘤的发生发展提供新的科学依据和防治靶标。

我们前期的工作表明，丝氨酸通路的活化对于肝癌细胞在营养压力微环境条件下的存活起着至关重要的作用，但外源添加丝氨酸并不能回补丝氨酸合成酶PHGDH或者PSPH缺失带来的增殖缺陷和周期紊乱，暗示丝氨酸代谢酶存在非代谢以外的功能并参与细胞增殖。本项目深入研究了丝氨酸代谢酶PSPH, PHGDH对周期异常的调控，取得了系列重要进展。我们发现：1）体内外IP及pull down实验表明PSPH直接结合Aurora A并在细胞分裂过程中二者共定位；2）PHGDH调控PLK1的蛋白表达，但不调控其mRNA水平；3）敲低PHGDH后进行周期同步化发现细胞阻滞在G2/M期；4）PHGDH调节线粒体的动态平衡并存在线粒体定位，后续这些蛋白改变对肿瘤细胞生物学行为以及肿瘤发生发展的影响仍在深入展开中；5）此外，为了进一步解析代谢酶通过非代谢功能参与肿瘤进展，我们发现肝癌细胞中PHGDH可易位至线粒体并与线粒体内膜蛋白ANT2结合招募线粒体翻译因子mtEFG2，通过增强线粒体核糖体的再循环效率，从而促进线粒体翻译和肝癌细胞增殖（Shu Y#, ……Sun L C*, The EMBO Journal, 2022）；6）同时，我们发现烯醇化酶ENO1作为RNA结合蛋白结合并降解IRP1 mRNA，从而调控细胞内铁离子的代谢稳态，影响铁死亡而促进肝癌的发生发展（Zhang T#, Sun L C#, et al., Nature Cancer, 2022）。在本项目资助下，共发表SCI论文8篇（包含1篇Nature Cancer, 两篇The EMBO Journal, 1篇Cancer Research），均标注了本基金的支持。总体而言，我们完成了各项预定的目标。申请人也获得了中央高校面上项目，基金委面上项目等的资助。