Vollenbröker Beate, George Britta, Wolfgart Maria, Saleem Moin A, Pavenstädt Hermann, Weide Thomas
UKM, Medizinische Klinik und Poliklinik D, Abteilung: Molekulare Nephrologie, Domagkstr. 3a, D-48149 Münster, Germany.
Am J Physiol Renal Physiol. 2009 Feb;296(2):F418-26. doi: 10.1152/ajprenal.90319.2008. Epub 2008 Nov 19.
The immunosuppressive mammalian target of rapamycin (mTOR) inhibitors can cause proteinuria, especially in kidney and heart transplanted patients. Podocytes play a major role in establishing the selective permeability of the blood-urine filtration barrier. Damage of these cells leads to proteinuria, a hallmark of most glomerular diseases. Interestingly, podocyte damage and focal segmental glomerulosclerosis can occur after treatment with an mTOR inhibitor in some transplant patients. To investigate the mechanisms of mTOR inhibitor-induced podocyte damage, we analyzed the effect of rapamycin on mTOR signaling and cellular function in human podocytes. We found that prolonged rapamycin treatment reduced the expression of total mTOR, which correlates with diminished levels of mTOR phosphorylation at Ser(2448) and Ser(2481). In addition, treatment with rapamycin reduced rictor expression and mTORC2 formation, resulting in a reduced phosphorylation of protein kinase B at Ser(473). The expression level of the slit-diaphragm proteins nephrin and transient receptor potential cation channel 6 as well as the cytoskeletal adaptor protein Nck significantly decreased. Moreover, rapamycin reduced cell adhesion and cell motility, which was accompanied by an enhanced formation of dot-like actin-rich structures. Our data provide new molecular insights explaining which pathways and molecules are affected in podocytes by an imbalanced mTOR function because of rapamycin treatment.
免疫抑制性雷帕霉素哺乳动物靶点（mTOR）抑制剂可导致蛋白尿，尤其是在肾移植和心脏移植患者中。足细胞在建立血-尿滤过屏障的选择性通透性方面起主要作用。这些细胞的损伤会导致蛋白尿，这是大多数肾小球疾病的一个标志。有趣的是，在一些移植患者中，使用mTOR抑制剂治疗后会出现足细胞损伤和局灶节段性肾小球硬化。为了研究mTOR抑制剂诱导足细胞损伤的机制，我们分析了雷帕霉素对人足细胞中mTOR信号传导和细胞功能的影响。我们发现，长时间的雷帕霉素治疗会降低总mTOR的表达，这与Ser（2448）和Ser（2481）处mTOR磷酸化水平的降低相关。此外，雷帕霉素治疗会降低rictor的表达和mTORC2的形成，导致蛋白激酶B在Ser（473）处的磷酸化减少。裂孔隔膜蛋白nephrin和瞬时受体电位阳离子通道6以及细胞骨架衔接蛋白Nck的表达水平显著降低。此外，雷帕霉素降低了细胞黏附和细胞运动能力，同时伴有富含肌动蛋白的点状结构形成增加。我们的数据提供了新的分子见解，解释了由于雷帕霉素治疗导致mTOR功能失衡，足细胞中的哪些信号通路和分子受到影响。
