Motonishi Shuta, Nangaku Masaomi, Wada Takehiko, Ishimoto Yu, Ohse Takamoto, Matsusaka Taiji, Kubota Naoto, Shimizu Akira, Kadowaki Takashi, Tobe Kazuyuki, Inagi Reiko
Divisions of Nephrology and Endocrinology and.
Divisions of Nephrology and Endocrinology and
J Am Soc Nephrol. 2015 Aug;26(8):1939-59. doi: 10.1681/ASN.2014030289. Epub 2014 Nov 25.
Recent studies have highlighted the renoprotective effect of sirtuin1 (SIRT1), a deacetylase that contributes to cellular regulation. However, the pathophysiologic role of SIRT1 in podocytes remains unclear. Here, we investigated the function of SIRT1 in podocytes. We first established podocyte-specific Sirt1 knockout (SIRT1(pod-/-)) mice. We then induced glomerular disease by nephrotoxic serum injection. The increase in urinary albumin excretion and BUN and the severity of glomerular injury were all significantly greater in SIRT1(pod-/-) mice than in wild-type mice. Western blot analysis and immunofluorescence showed a significant decrease in podocyte-specific proteins in SIRT1(pod-/-) mice, and electron microscopy showed marked exacerbation of podocyte injury, including actin cytoskeleton derangement in SIRT1(pod-/-) mice compared with wild-type mice. Protamine sulfate-induced podocyte injury was also exacerbated by podocyte-specific SIRT1 deficiency. In vitro, actin cytoskeleton derangement in H2O2-treated podocytes became prominent when the cells were pretreated with SIRT1 inhibitors. Conversely, this H2O2-induced derangement was ameliorated by SIRT1 activation. Furthermore, SIRT1 activation deacetylated the actin-binding and -polymerizing protein cortactin in the nucleus and facilitated deacetylated cortactin localization in the cytoplasm. Cortactin knockdown or inhibition of the nuclear export of cortactin induced actin cytoskeleton derangement and dissociation of cortactin from F-actin, suggesting the necessity of cytoplasmic cortactin for maintenance of the actin cytoskeleton. Taken together, these findings indicate that SIRT1 protects podocytes and prevents glomerular injury by deacetylating cortactin and thereby, maintaining actin cytoskeleton integrity.
近期研究强调了沉默调节蛋白1（SIRT1）的肾脏保护作用，SIRT1是一种参与细胞调节的去乙酰化酶。然而，SIRT1在足细胞中的病理生理作用仍不清楚。在此，我们研究了SIRT1在足细胞中的功能。我们首先建立了足细胞特异性Sirt1基因敲除（SIRT1(pod-/-)）小鼠。然后通过注射肾毒性血清诱导肾小球疾病。与野生型小鼠相比，SIRT1(pod-/-)小鼠的尿白蛋白排泄量、血尿素氮增加以及肾小球损伤的严重程度均显著更高。蛋白质印迹分析和免疫荧光显示，SIRT1(pod-/-)小鼠中足细胞特异性蛋白显著减少，电子显微镜显示足细胞损伤明显加重，与野生型小鼠相比，SIRT1(pod-/-)小鼠中包括肌动蛋白细胞骨架紊乱。硫酸鱼精蛋白诱导的足细胞损伤也因足细胞特异性SIRT1缺乏而加剧。在体外，当用SIRT1抑制剂预处理细胞时，过氧化氢处理的足细胞中的肌动蛋白细胞骨架紊乱变得更加明显。相反，SIRT1激活改善了这种过氧化氢诱导的紊乱。此外，SIRT1激活使细胞核中的肌动蛋白结合和聚合蛋白皮层肌动蛋白去乙酰化，并促进去乙酰化的皮层肌动蛋白在细胞质中的定位。皮层肌动蛋白敲低或抑制皮层肌动蛋白的核输出会诱导肌动蛋白细胞骨架紊乱以及皮层肌动蛋白与F-肌动蛋白解离，这表明细胞质中的皮层肌动蛋白对于维持肌动蛋白细胞骨架是必需的。综上所述，这些发现表明SIRT1通过使皮层肌动蛋白去乙酰化从而维持肌动蛋白细胞骨架完整性来保护足细胞并预防肾小球损伤。
