mTOR信号通路介导的APOBEC-1互补因子对肾脏发育调控的分子机制研究

The kidney is an essential organ whose malformations severely impair human health. The development of human kidney is a complex process that requires coordinated cell growth and differentiation under temporal and spatial regulation, yet the genetic regulation of this process remains unclear. A1cf is essential for fetal development as the deletion leads to embryonic lethality in mice. Our previous study has shown high degree conservation of a1cf sequence, with alternative splicing features, and specific temporal and spatial expression pattern in the developing kidney, suggesting the novel role for a1cf in renal development. We have also found a1cf specific combination site in Rictor, which is a critical protein composing mTORc2; and enhanced Rictor mRNA level was observed in the condition of a1cf over-expression, suggesting the possibility of a novel a1cf-rictor-mTOR regulatory pathway in renal development. In this study, we intend to clarify the regulatory mechanism of a1cf towards Rictor, verify the a1cf-rictor-mTOR pathway, and perform further a1cf functional studies in Xenopus and genetically engineered mouse model. This study would promote the understanding of molecular mechanism in renal development, providing new ideas on prevention and treatment of renal developmental disorders.

肾脏是人体重要器官之一，其发育异常严重危害人类健康。肾脏也是器官发育研究经典模型之一，在发育中受到精确的时空调控，其分子机制有待深入研究。我们前期研究发现APOBEC-1互补因子（a1cf）在肾脏发育中存在时空表达特异性，其序列在进化上高度保守，具有选择性剪切特性，提示a1cf可能为调控肾脏发育的新基因；首次发现a1cf能识别mTOR信号通路关键分子rictor，并调节其表达。已知mTOR对细胞生长、代谢及衰老等重要生命过程起中心调控作用，是肾脏发育关键调控通路之一。a1cf对rictor的调控提示a1cf可能通过mTOR信号通路影响肾脏发育。本研究将回答a1cf是否为肾脏发育分子调控新基因，a1cf-rictor-mTOR调控通路是否存在；加深肾脏发育中mTOR信号通路的理解，完善肾脏发育分子调控网络；明确肾脏a1cf条件性敲除的影响，探索a1cf在肾脏发育相关疾病的预防和治疗中的作用

Apobec-1互补因子(A1CF)属于不均一核糖核蛋白（hnRNP）家族，它主要是参与载脂蛋白B(apoB)的转录后编辑过程。在小肠中，A1CF介导的apoB的mRNA转录后编辑对其脂质的吸收是必需的。早期对于A1CF的研究仅局限在小肠和肝脏中，我们的研究首次报道了A1CF 在肾脏和乳腺中的生物学功能。在肾脏中，原位杂交结果显示A1CF在C57BL/6小鼠肾脏发育早期不表达，自胚胎期15.5天开始表达，并且在成年肾脏中集中表达在肾小管中；在大鼠肾脏近曲小管上皮细胞中利用western-blot和免疫荧光技术发现，A1CF可抑制该细胞的上皮-间质转化过程及细胞迁移能力；我们的研究还发现，A1CF的两种变体A1CF和A1CF(-8AA)具有不同的细胞定位，A1CF定位于细胞核中，A1CF(-8AA)定位于细胞质中。在乳腺癌细胞中，EdU实验和western-blot结果表明A1CF(-8AA)能够促进乳腺癌细胞增殖，通过对其机制的研究发现，这一促进作用是通过A1CF(-8AA)稳定IL-6实现的；另一方面，A1CF亦可结合于DKK1的3ʹUTR促进DKK1的表达，并进一步抑制与之相关的Wnt信号通路，从而促进乳腺癌细胞迁移能力，抑制细胞凋亡。综上我们的研究首次证明了A1CF在肾脏发育过程中的表达并发现了A1CF可抑制大鼠近曲小管细胞的上皮-间质转化及其迁移能力。此外，我们还发现A1CF/A1CF(-8AA)具有不同的亚细胞定位，A1CF亦能促进乳腺癌细胞的增殖与细胞迁移能力、抑制细胞的凋亡，从而实现对于A1CF生物学功能的拓展。