Louis Stokes Cleveland Veteran Affairs Medical Center, Case Western Reserve University, USA.
Exp Cell Res. 2012 Jun 10;318(10):1075-85. doi: 10.1016/j.yexcr.2012.03.011. Epub 2012 Mar 26.
The glomerular capillary wall, composed of endothelial cells, the glomerular basement membrane and the podocytes, is continually subjected to hemodynamic force arising from tractional stress due to blood pressure and shear stress due to blood flow. Exposure of glomeruli to abnormal hemodynamic force such as hyperfiltration is associated with glomerular injury and progressive renal disease, and the conversion of mechanical stimuli to chemical signals in the regulation of the process is poorly understood in podocytes. By examining DNA fragmentation, apoptotic nuclear changes and cytochrome c release, we found that shear stress induced cell apoptosis in cultured podocytes. Meanwhile, podocytes exposed to shear stress also stimulated c-Src phosphorylation, phospholipase D (PLD) activation and mammalian target of rapamycin (mTOR) signaling. Using the antibodies against c-Src, PLD(1), and PLD(2) to perform reciprocal co-immunoprecipitations and in vitro PLD activity assay, our data indicated that c-Src interacted with and activated PLD(1) but not PLD(2). The inhibition of shear stress-induced c-Src phosphorylation by PP(2) (a specific inhibitor of c-Src kinase) resulted in reduced PLD activity. Phosphatidic acid, produced by shear stress-induced PLD activation, stimulated mTOR signaling, and caused podocyte hypertrophy and apoptosis.
肾小球毛细血管壁由内皮细胞、肾小球基底膜和足细胞组成，它不断受到由血压引起的牵拉力和由血流引起的切应力等血流动力的作用。肾小球暴露于异常的血流动力，如超滤，与肾小球损伤和进行性肾脏疾病有关，而足细胞中机械刺激向化学信号的转化在调节过程中了解甚少。通过检查 DNA 片段化、凋亡核变化和细胞色素 c 释放，我们发现剪切力诱导培养的足细胞发生细胞凋亡。同时，暴露于剪切力的足细胞也刺激 c-Src 磷酸化、磷脂酶 D（PLD）的激活和哺乳动物雷帕霉素靶蛋白（mTOR）信号。使用针对 c-Src、PLD(1) 和 PLD(2) 的抗体进行相互共免疫沉淀和体外 PLD 活性测定，我们的数据表明 c-Src 与 PLD(1)相互作用并激活 PLD(1)，但不激活 PLD(2)。PP(2)（c-Src 激酶的特异性抑制剂）抑制剪切力诱导的 c-Src 磷酸化导致 PLD 活性降低。由剪切力诱导的 PLD 激活产生的磷酸脂酸刺激 mTOR 信号，导致足细胞肥大和凋亡。
