Identification of the protein homeostasis network that controls the quality contr

描述（由申请人提供）：遗传性von Hippel-Lindau病的患者由于编码von Hippel-Lindau肿瘤抑制蛋白（pVHL）的基因突变而发展为视网膜、小脑和脊髓血管母细胞瘤以及肾癌、胰腺和附睾肿瘤。pVHL通常作为E3泛素连接酶复合物的适配器来调节转录因子HIF-1的活性。当细胞氧水平降低时，HIF-1¿被激活并上调细胞增殖因子，导致细胞生长。在没有功能性pVHL的情况下，HIF-1¿的失调会导致不受控制的细胞生长，而不管氧水平如何。Frydman实验室的研究表明，pVHL的正常折叠和功能需要pVHL与伴侣蛋白Hsp70和大细胞质异聚体伴侣蛋白TriC之间的相互作用。折叠后的pVHL能够与长链B和C形成复合物（这里是长链BC），这是pVHL稳定性所必需的一个步骤。pvhl -长链蛋白BC复合物（VBC），当与scfe3泛素连接酶复合物结合时，在氧气存在下指导HIF-1¿的蛋白水解降解。因此，pVHL的适当折叠和功能涉及由伴侣和蛋白酶体机制介导的几个蛋白质质量控制“检查点”。重要的是，一些导致VHL疾病的突变体具有实现折叠的潜力，但未能通过这些质量控制检查点的作用来实现折叠，从而导致其降解。pVHL突变体的蛋白水解降解机制尚不清楚。本研究的长期目标是确定细胞蛋白折叠和降解机制如何合作以维持肿瘤抑制蛋白pVHL的质量控制。在这里，我们建议确定在易于操纵的酵母系统中肿瘤突变的伴侣和蛋白水解降解质量控制要求，然后确定这些机制是否在哺乳动物细胞中保守。这种理解可能会导致治疗策略，以恢复这些突变蛋白的功能在受影响的患者。由于其他病理过程，包括其他癌症，都是由影响关键调节蛋白折叠或稳定性的突变引起的，因此VHL的结果可能提供具有广泛概念和治疗意义的范例。

DESCRIPTION (provided by applicant): Patients afflicted with hereditary von Hippel-Lindau disease develop retinal, cerebellar and spinal cord hemangioblastomas as well as renal carcinomas and tumors of the pancreas and epididymis due to mutations in the gene encoding von Hippel-Lindau tumor suppressor protein (pVHL). pVHL normally functions as an adapter in an E3 ubiquitin ligase complex to regulate the activity of the transcription factor, HIF-1¿. When cellular oxygen levels are reduced, HIF-1¿ is activated and upregulates cellular proliferation factors resulting in cell growth. In the absence of functional pVHL, dysregulation of HIF-1¿ can lead to uncontrolled cell growth regardless of oxygen levels. Studies from the Frydman laboratory have demonstrated that proper folding and functionality of pVHL requires an interaction between pVHL and the chaperone Hsp70 and the large cytosolic heterooligomeric chaperonin TriC. Folded pVHL is then competent to form a complex with elongins B and C (herein elongin BC), a step that is required for pVHL stability. The pVHL-elongin BC complex (VBC), when incorporated into the SCF E3 ubiquitin ligase complex, directs the proteolytic degradation of HIF-1¿ in the presence of oxygen. Thus, proper folding and functionality of pVHL involves several protein quality control "checkpoints" mediated by chaperone and proteasomal machinery. Importantly, some of the mutants leading to VHL disease have the potential to achieve folding, but fail to do so through the action of these quality control checkpoints that result in their degradation. The mechanism of proteolytic degradation of pVHL mutants is unclear. The long-term goal of this research is to determine how cellular protein folding and degradation machinery cooperate to maintain quality control of the tumor suppressor protein pVHL. Here we propose to determine the chaperone and proteolytic degradation quality control requirements of tumor-causing mutations in the easily manipulated yeast system and then determine if these mechanisms are conserved in mammalian cells. This understanding may lead to therapeutic strategies to restore the function of these mutant proteins in affected patients. Since other pathological processes, including other cancers, are caused by mutations that affect the folding or stability of key regulatory proteins, the results obtained for VHL may provide a paradigm with broad conceptual and therapeutic implications. PUBLIC HEALTH RELEVANCE: Patients with hereditary von Hippel-Lindau disease have the potential to develop a variety of tumors including hemangioblastomas in retinal, cerebellar and spinal cord tissue as well as renal carcinomas and tumors of the pancreas and epididymis. The basis of tumor formation in these patients is due to mutations in the von Hippel- Lindau tumor suppressor protein (pVHL), a protein that normally functions to keep cell division in check. In this proposal, we will determine the mechanism by which the cell recognizes and processes mutant pVHL protein in an effort to identify therapies by which normal pVHL function can be restored in human cells.