The R2TP-complex in the molecular pathogenesis of cystic kidney diseases and in ciliary biology

近年来的研究表明，原发性纤毛在囊性肾病（包括常见的常染色体显性遗传性多囊肾病（ADPKD）和一些罕见的常染色体隐性遗传综合征性疾病）的发病机制中起着重要作用。在肾脏中，初级纤毛像天线一样从肾小管上皮细胞的顶端表面伸入小管腔。作为感觉细胞器，它们将来自环境的信号传递到细胞中。纤毛是在分裂间期形成的，在有丝分裂重新进入之前必须被重吸收。纤毛动力学的详细机制和纤毛在肾脏中的功能还没有得到很好的理解。当进行基于蛋白质组学的相互作用筛选与囊性肾病蛋白肾囊蛋白-1作为诱饵，我们确定了AAA+蛋白酶和核心成分的R2 TP复合物Ruvbl 1和Ruvbl 2的肾囊蛋白复合物，这是主要位于纤毛基地的新成分。假设Ruvbl 1/2在囊性肾病中的作用，我们产生了条件性敲除小鼠。有趣的是，肾小管上皮细胞特异性表达cre的动物发展为严重的退行性囊性肾病。此外，我们可以确定新的肾胱氨酸和R2 TP复合物之间的分子联系。R2 TP复合物是HSP 90的共伴侣，其促进Box C/D小核仁核糖核蛋白（snoRNP）的合成和前核糖体RNA的加工，从而影响细胞的整体蛋白质生物合成。 该提议检验了Ruvbl 1/2和R2 TP复合物在囊性肾的发病机制和纤毛生物学中起重要作用的假设。具体而言，我们的目标是（1）详细分析Ruvb 11和Ruvb 12在体内肾小管上皮中的重要性，（2）表征R2 TP-伴侣蛋白复合物作为肾胱氨酸复合物的调节剂以及初级纤毛的蛋白质组成，以及（3）阐明纤毛和纤毛蛋白在多大程度上调节R2 TP复合物在核糖体生物发生和mTOR调节中的活性活动

Recent exciting work has demonstrated that primary cilia play an important role in the pathogenesis of cystic kidney diseases, which include the frequent autosomal-dominant polycystic kidney disease (ADPKD) as well as a number of rare autosomal-recessive syndromic diseases. In the kidney, primary cilia project like antennae from the apical surface of tubular epithelial cells into the lumen of the tubules. Acting as sensory organelles they transmit signals from the environment into the cell. Cilia are built during interphase and have to be reabsorbed before mitotic re-entry. The detailed mechanism of ciliary dynamic and the function of cilia in the kidney are not well understood.When performing a proteomics-based interaction screen with the cystic kidney disease protein nephrocystin-1 as bait we identified the AAA+ proteases and core-components of the R2TP complex Ruvbl1 and Ruvbl2 as novel constituents of the nephrocystin protein complex, which is predominantly localized at the ciliary base. Assuming a role for Ruvbl1/2 in cystic kidney disease we generated a conditional knockout mouse. Interestingly, animals with cre expression specific to the tubular epithelium developed a severe degenerative cystic kidney disease. Moreover, we could identify novel molecular links between nephrocystins and the R2TP-complex. The R2TP-complex is a co-chaperone for HSP90 that promotes both the synthesis of Box C/D small nucleolar ribonucleoproteins (snoRNPs) and the processing of pre-ribosomal RNA, thereby influencing the global protein biosynthesis of cells. This proposal tests the hypothesis that Ruvbl1/2 and the R2TP-complex play vital roles in the pathogenesis of cystic kidneys and in ciliary biology. Specifically, we aim (1) to analyze in detail the importance of Ruvbl1 and Ruvbl2 in tubular epithelium in vivo, (2) to characterize the R2TP-chaperone-complex as a regulator of the nephrocystin-complex as well as the protein composition of primary cilia, and (3) to clarify to what extent cilia and ciliary proteins modulate the activity of the R2TP complex in the regulation of ribosome biogenesis and mTOR activity.