Dong Heling, Chen Zhenguo, Wang Caixia, Xiong Zhi, Zhao Wanlu, Jia Chunhong, Lin Jun, Lin Yan, Yuan Weiping, Zhao Allan Z, Bai Xiaochun
State Key Laboratory of Organ Failure Research (H.D., Z.C., C.W., Z.X., W.Z., C.J., J.L., X.B.), Department of Cell Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, China; State Key Laboratory of Reproductive Medicine (L.Y., A.Z.Z.), The Center of Metabolic Disease Research, Nanjing Medical University, Nanjing, Jiangsu Province 210029, China; and State Key Laboratory of Experimental Hematology (W.Y.), Institute of Hematology; and Blood Diseases Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin 300020, China.
Endocrinology. 2015 Nov;156(11):4244-56. doi: 10.1210/en.2015-1217. Epub 2015 Sep 11.
Maintenance of cell polarity is essential for Sertoli cell and blood-testis barrier (BTB) function and spermatogenesis; however, the signaling mechanisms that regulate the integrity of the cytoskeleton and polarity of Sertoli cells are not fully understood. Here, we demonstrate that rapamycin-insensitive component of target of rapamycin (TOR) (Rictor), a core component of mechanistic TOR complex 2 (mTORC2), was expressed in the seminiferous epithelium during testicular development, and was down-regulated in a cadmium chloride-induced BTB damage model. We then conditionally deleted the Rictor gene in Sertoli cells and mutant mice exhibited azoospermia and were sterile as early as 3 months old. Further study revealed that Rictor may regulate actin organization via both mTORC2-dependent and mTORC2-independent mechanisms, in which the small GTPase, ras-related C3 botulinum toxin substrate 1, and phosphorylation of the actin filament regulatory protein, Paxillin, are involved, respectively. Loss of Rictor in Sertoli cells perturbed actin dynamics and caused microtubule disarrangement, both of which accumulatively disrupted Sertoli cell polarity and BTB integrity, accompanied by testicular developmental defects, spermiogenic arrest and excessive germ cell loss in mutant mice. Together, these findings establish the importance of Rictor/mTORC2 signaling in Sertoli cell function and spermatogenesis through the maintenance of Sertoli cell cytoskeletal dynamics, BTB integrity, and cell polarity.
维持细胞极性对于支持细胞和血睾屏障（BTB）功能以及精子发生至关重要；然而，调节支持细胞细胞骨架完整性和极性的信号机制尚未完全明确。在此，我们证明雷帕霉素靶蛋白（TOR）的雷帕霉素不敏感成分（Rictor），即机械性TOR复合物2（mTORC2）的核心成分，在睾丸发育过程中表达于生精上皮，并在氯化镉诱导的BTB损伤模型中表达下调。然后，我们在支持细胞中条件性敲除Rictor基因，突变小鼠早在3个月大时就表现出无精子症且不育。进一步研究表明，Rictor可能通过mTORC2依赖性和mTORC2非依赖性机制调节肌动蛋白组织，其中分别涉及小GTP酶、Ras相关C3肉毒杆菌毒素底物1和肌动蛋白丝调节蛋白桩蛋白的磷酸化。支持细胞中Rictor的缺失扰乱了肌动蛋白动力学并导致微管排列紊乱，这两者共同破坏了支持细胞极性和BTB完整性，同时伴有突变小鼠的睾丸发育缺陷、精子发生停滞和大量生殖细胞丢失。总之，这些发现通过维持支持细胞细胞骨架动力学、BTB完整性和细胞极性，确立了Rictor/mTORC2信号在支持细胞功能和精子发生中的重要性。
