Rapamycin引起雄性不育和mTOR信号通路调控精子发生的分子机制研究

Rapamycin is an inhibitor of the mTOR(mammalian Target of Rapamycin),it suppresses cell proliferation,promotes stem cell self-renewal capacity,regulates autophagy and extends lifespan in mice. Rapamycin and its analogs(rapalogs) are now FDA approved as immunosuppressants and anticancer agents which are widely used in organ transplanted and cancer patients. However,there are many reports regarding rapamycin's undesirable side effects, one of which is the reduced fertility observed in male kidney transplanted recipients. mTOR is an serine/threonine protein kinase, which forms two large distinct complexes mTORC1 and mTORC2 through interacting with different proteins.mTORC1 regulates ribosome biogenesis and protein translation via phosphorating downstream targets including S6 kinase1(S6K1) and eukaryotic translation initiation factor 4E-binding protein(4E-BP1).mTORC2 plays an essential role in glucose metabolism and the cytoskeleton through AKT,serum/glucocorticoid induced kinase(SGK) and protein kinase C(PKC-α).Our study will systemically uncover changes in mTOR signaling pathway and spermatogenesis in rapamycin treated mice, and reveal the underlying mechanism accounting for infertility in rapamycin treated mice. This study will provide fundamental basis for designing next generation of rapalogs.

雷帕霉素(rapamycin)是哺乳动物雷帕霉素靶蛋白(mTOR)的抑制剂, 它抑制细胞增殖，增强干细胞的自我更新功能，促进细胞自噬和延长小鼠的寿命。目前rapamycin和它的类似物rapalogs广泛用于器官移植和癌症治疗，但临床上接受rapamycin作为免疫抑制剂的男性病人中，出现了不育的症状。mTOR是一类丝氨酸/苏氨酸蛋白激酶,在体内形成mTORC1和mTORC2两种不同复合体。mTORC1复合体通过S6K1和4E-BP1调控核糖体的生物合成和蛋白翻译；mTORC2复合体通过AKT, SGK和PKCα调控血糖代谢和细胞骨架。我们将通过分析rapamycin处理小鼠的生殖表型，利用睾丸生殖细胞特异性Raptor(mTORC1)或Rictor(mTORC2)敲除小鼠，深入阐述rapamycin引起雄性不育的分子机制，为设计和开发新一代特异性的rapalogs提供理论基础。

mTOR ( Mechanistic target of rapamycin)是生物体内保守的丝氨酸/苏氨酸蛋白激酶，调控细胞生长和代谢。mTOR与不同的小分子蛋白形成mTORC1和mTORC2两种不同的复合体，通过下游靶向蛋白发挥功能。本项目旨在探究mTOR信号通路在生精过程中的功能和作用机理，构建了三种遗传学小鼠模型：1）Vasa-Cre介导的mTORC1复合体特异组成蛋白Raptor条件性敲除模型，阐明mTORC1信号通路在精原细胞自我更新中的功能；2）构建了Ngn3-Cre介导的Raptor基因条件性敲除小鼠，发现敲除小鼠阻滞在粗线期精母细胞，并调控染色体的联会和性染色体沉默；3）制备了小分子药物rapamycin长期处理的小鼠，模拟长寿小鼠的模型，发现长寿剂量的rapapmycin引起粗线期性染色体基因异常升高，同时改变piRNA通路中PIWI相关蛋白的定位。此外，本项目延伸发现哺乳动物piRNA 3’端剪切酶PNLDC1和单倍体圆形精子发育中关键转录因子Sox30。