Department II of Internal Medicine, University Hospital Cologne, Cologne, Germany.
Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany.
FASEB J. 2018 Sep;32(9):4696-4713. doi: 10.1096/fj.201701307R. Epub 2018 Apr 25.
Podocytes are highly specialized, epithelial, postmitotic cells, which maintain the renal filtration barrier. When adapting to considerable metabolic and mechanical stress, podocytes need to accurately maintain their proteome. Immortalized podocyte cell lines are a widely used model for studying podocyte biology in health and disease in vitro. In this study, we performed a comprehensive proteomic analysis of the cultured human podocyte proteome in both proliferative and differentiated conditions at a depth of >7000 proteins. Similar to mouse podocytes, human podocyte differentiation involved a shift in proteostasis: undifferentiated podocytes have high expression of proteasomal proteins, whereas differentiated podocytes have high expression of lysosomal proteins. Additional analyses with pulsed stable-isotope labeling by amino acids in cell culture and protein degradation assays determined protein dynamics and half-lives. These studies unraveled a globally increased stability of proteins in differentiated podocytes. Mitochondrial, cytoskeletal, and membrane proteins were stabilized, particularly in differentiated podocytes. Importantly, protein half-lives strongly contributed to protein abundance in each state. These data suggest that regulation of protein turnover of particular cellular functions determines podocyte differentiation, a paradigm involving mitophagy and, potentially, of importance in conditions of increased podocyte stress and damage.-Schroeter, C. B., Koehler, S., Kann, M., Schermer, B., Benzing, T., Brinkkoetter, P. T., Rinschen, M. M. Protein half-life determines expression of proteostatic networks in podocyte differentiation.
足细胞是高度特化的上皮细胞，属于有丝分裂后细胞，能够维持肾脏的滤过屏障。在适应巨大的代谢和机械压力时，足细胞需要准确地维持其蛋白质组。永生化的足细胞系是体外研究足细胞生物学在健康和疾病中的广泛应用模型。在这项研究中，我们对培养的人类足细胞蛋白质组在增殖和分化条件下进行了深度超过 7000 种蛋白质的全面蛋白质组分析。与小鼠足细胞相似，人类足细胞分化涉及到蛋白质稳态的转变：未分化的足细胞高表达蛋白酶体蛋白，而分化的足细胞高表达溶酶体蛋白。利用脉冲稳定同位素标记氨基酸在细胞培养和蛋白质降解测定中的进一步分析，确定了蛋白质动力学和半衰期。这些研究揭示了分化的足细胞中蛋白质整体稳定性的增加。线粒体、细胞骨架和膜蛋白被稳定，特别是在分化的足细胞中。重要的是，蛋白质半衰期强烈影响每个状态下的蛋白质丰度。这些数据表明，特定细胞功能的蛋白质周转率的调节决定了足细胞的分化，这一范例涉及到自噬，并且在增加的足细胞应激和损伤的情况下可能具有重要意义。-Schroeter，C. B.，Koehler，S.，Kann，M.，Schermer，B.，Benzing，T.，Brinkkoetter，P. T.，Rinschen，M. M. 蛋白质半衰期决定了足细胞分化中蛋白质稳态网络的表达。
