Department of Nephrology, The Second Affiliated Hospital, GuangZhou Medical University, 250th, Chang Gang East Road, Guangzhou, 510260, China.
Department of General Internal Medicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.
Int Urol Nephrol. 2018 May;50(5):983-991. doi: 10.1007/s11255-018-1787-z. Epub 2018 Jan 24.
Podocyte damage exerts a key role in proteinuria. We have demonstrated that calcineurin-binding protein 1 (Cabin1) upregulated during podocyte injury, yet its function in podocyte is still unclear.
We established 5/6 nephrectomized rats and angiotensin II (AngII)-injured podocyte, as well as knocked down Cabin1 with siRNA in cultured podocytes. Rats were killed at 4 or 8 weeks after 5/6 nephrectomy. The localization of podocyte cytoskeleton was detected after immunofluorescence staining. Podocyte mitochondrial morphology was observed under electron microscopy. Podocyte mitochondrial transmembrane potential (MMP) was measured with MitoCapture kit. Cabin1 and cytochrome c protein expression were detected by western blot.
Massive proteinuria, as well as obvious segmental glomerular sclerosis, was found in rats at 8 weeks after nephrectomy, accompanied with the disruption of synaptopodin. Moreover, mitochondria changed from large and ellipsoid shape to the small, long, and irregular shape in rats at 4 weeks after operation. At 8 weeks, mitochondria were swollen and cristae were remarkably dissolved. Compared to sham-operated rats, Cabin1 protein expression was obviously upregulated in rats at 8 weeks. AngII induced the decrease in MMP, as well as the overexpression of Cabin1 and cytochrome c protein in podocytes. Knocking down Cabin1 induced the disruption of F-actin and overexpression of cytochrome c (1.81 ± 0.21 in siRNA group vs. 0.86 ± 0.11 in negative control group).
Knocking down Cabin1 induces the disruption of cytoskeleton and mitochondrial dysfunction in podocyte. Cabin1 could be a crucial factor in podocyte damage.
足细胞损伤在蛋白尿中起关键作用。我们已经证明，在足细胞损伤过程中钙调神经磷酸酶结合蛋白 1（Cabin1）上调，但它在足细胞中的功能尚不清楚。
我们建立了 5/6 肾切除大鼠和血管紧张素 II（AngII）损伤的足细胞，以及用 siRNA 在培养的足细胞中敲低 Cabin1。5/6 肾切除后 4 或 8 周处死大鼠。免疫荧光染色后检测足细胞细胞骨架的定位。电镜下观察足细胞线粒体形态。用 MitoCapture 试剂盒测量足细胞线粒体跨膜电位（MMP）。Western blot 检测 Cabin1 和细胞色素 c 蛋白表达。
大量蛋白尿，以及明显的节段性肾小球硬化，在肾切除后 8 周的大鼠中发现，伴随着突触蛋白的破坏。此外，在手术后 4 周的大鼠中，线粒体从大而椭圆形变为小而长而不规则的形状。在 8 周时，线粒体肿胀，嵴明显溶解。与假手术大鼠相比，在 8 周时大鼠的 Cabin1 蛋白表达明显上调。AngII 诱导 MMP 下降，以及足细胞中 Cabin1 和细胞色素 c 蛋白的过度表达。敲低 Cabin1 诱导 F-肌动蛋白的破坏和细胞色素 c 的过度表达（siRNA 组为 1.81±0.21，阴性对照组为 0.86±0.11）。
敲低 Cabin1 诱导足细胞骨架破坏和线粒体功能障碍。Cabin1 可能是足细胞损伤的关键因素。
