Department of Pathology, School of Basic Medical Sciences, Fudan University, Shanghai, China.
Cell Death Dis. 2019 Mar 11;10(3):241. doi: 10.1038/s41419-019-1480-x.
Podocyte loss is one of the determining factors for the progression toward glomerulosclerosis. Podocyte is terminally differentiated and does not typically proliferate following injury and loss. However, recent evidence suggested that during renal injury, podocyte could re-enter the cell cycle, sensitizing the cells to injury and death, but the molecular mechanisms underlying it, as well as the cell fate determination still remained unclear. Here, using NPHS2 Cre; mT/mG transgenic mice and primary podocytes isolated from the mice, we investigated the effect of mammalian target of rapamycin complex 1 (mTORC1)/4E-binding protein 1 (4E-BP1) signaling pathway on cell cycle re-entry and apoptosis of podocyte induced by adriamycin. It was found that podocyte cell cycle re-entry could be induced by adriamycin as early as the 1st week in vivo and the 2nd hour in vitro, accompanied with 4E-BP1 activation and was followed by podocyte loss or apoptosis from the 4th week in vivo or the 4th hour in vitro. Importantly, targeting 4E-BP1 activation by the RNA interference of 4E-BP1 or pharmacologic rapamycin (inhibitor of mTORC1, blocking mTORC1-dependent phosphorylation of its substrate 4E-BP1) treatment was able to inhibit the increases of PCNA, Ki67, and the S-phase fraction of cell cycle in primary podocyte during 2-6 h of adriamycin treatment, and also attenuated the following apoptotic cell death of podocyte detected from the 4th hour, suggesting that 4E-BP1 could be a regulator to manipulate the amount of cell cycle re-entry provided by differentiated podocyte, and thus regulate the degree of podocyte apoptosis, bringing us a new potential podocyte-protective substance that can be used for therapy.
足细胞丢失是肾小球硬化进展的决定因素之一。足细胞是终末分化的，在损伤和丢失后通常不会增殖。然而，最近的证据表明，在肾脏损伤过程中，足细胞可以重新进入细胞周期，使细胞对损伤和死亡敏感，但其中的分子机制以及细胞命运决定仍然不清楚。在这里，我们使用 NPHS2 Cre;mT/mG 转基因小鼠和从小鼠中分离的原代足细胞，研究了雷帕霉素复合物 1（mTORC1）/4E 结合蛋白 1（4E-BP1）信号通路对阿霉素诱导的足细胞细胞周期再进入和凋亡的影响。结果发现，阿霉素可以在体内第 1 周和体外第 2 小时诱导足细胞细胞周期再进入，伴随着 4E-BP1 的激活，随后在体内第 4 周或体外第 4 小时出现足细胞丢失或凋亡。重要的是，通过 4E-BP1 的 RNA 干扰或雷帕霉素（mTORC1 的抑制剂，阻断 mTORC1 依赖性磷酸化其底物 4E-BP1）处理靶向 4E-BP1 激活，能够抑制阿霉素处理后 2-6 小时原代足细胞中 PCNA、Ki67 和细胞周期 S 期分数的增加，并减弱随后从第 4 小时开始检测到的足细胞凋亡性死亡，表明 4E-BP1 可以作为调节分化的足细胞细胞周期再进入数量的调节剂，从而调节足细胞凋亡的程度，为我们提供了一种新的潜在的足细胞保护物质，可用于治疗。
