Grahammer Florian, Ramakrishnan Suresh K, Rinschen Markus M, Larionov Alexey A, Syed Maryam, Khatib Hazim, Roerden Malte, Sass Jörn Oliver, Helmstaedter Martin, Osenberg Dorothea, Kühne Lucas, Kretz Oliver, Wanner Nicola, Jouret Francois, Benzing Thomas, Artunc Ferruh, Huber Tobias B, Theilig Franziska
Department of Medicine IV, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Institute of Anatomy, Department of Medicine, University of Fribourg, Fribourg, Switzerland.
J Am Soc Nephrol. 2017 Jan;28(1):230-241. doi: 10.1681/ASN.2015111224. Epub 2016 Jun 13.
Renal proximal tubular cells constantly recycle nutrients to ensure minimal loss of vital substrates into the urine. Although most of the transport mechanisms have been discovered at the molecular level, little is known about the factors regulating these processes. Here, we show that mTORC1 and mTORC2 specifically and synergistically regulate PTC endocytosis and transport processes. Using a conditional mouse genetic approach to disable nonredundant subunits of mTORC1, mTORC2, or both, we showed that mice lacking mTORC1 or mTORC1/mTORC2 but not mTORC2 alone develop a Fanconi-like syndrome of glucosuria, phosphaturia, aminoaciduria, low molecular weight proteinuria, and albuminuria. Interestingly, proteomics and phosphoproteomics of freshly isolated kidney cortex identified either reduced expression or loss of phosphorylation at critical residues of different classes of specific transport proteins. Functionally, this resulted in reduced nutrient transport and a profound perturbation of the endocytic machinery, despite preserved absolute expression of the main scavenger receptors, MEGALIN and CUBILIN. Our findings highlight a novel mTOR-dependent regulatory network for nutrient transport in renal proximal tubular cells.
肾近端小管细胞不断循环利用营养物质，以确保重要底物极少流失到尿液中。尽管大多数转运机制已在分子水平上被发现，但对于调节这些过程的因素却知之甚少。在此，我们表明mTORC1和mTORC2特异性且协同地调节近端小管细胞（PTC）的内吞作用和转运过程。通过使用条件性小鼠遗传学方法使mTORC1、mTORC2或两者的非冗余亚基失活，我们发现缺乏mTORC1或mTORC1/mTORC2而非单独缺乏mTORC2的小鼠会出现类似范科尼综合征的症状，包括糖尿、磷酸盐尿、氨基酸尿、低分子量蛋白尿和白蛋白尿。有趣的是，对新鲜分离的肾皮质进行蛋白质组学和磷酸蛋白质组学分析发现，不同类别的特定转运蛋白的关键残基处存在表达降低或磷酸化缺失的情况。在功能上，尽管主要清道夫受体MEGALIN和CUBILIN的绝对表达得以保留，但这导致了营养物质转运减少以及内吞机制的严重紊乱。我们的研究结果突出了一种新的mTOR依赖性调节网络，用于肾近端小管细胞中的营养物质转运。
