Protein degradation and cholesterol regulation

蛋白质降解和胆固醇调节

• 批准号: 7197131
• 负责人: Randolph Y. Hampton
• 金额: $ 31.07万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN DIEGO
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-01-01 至 2012-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7197131
• 关键词: Address; Area; Binding; Biochemical; Biochemical Genetics; Biological Assay; Cholesterol; Complex; Condition; Degradation Pathway; Endoplasmic Reticulum; Endoplasmic Reticulum Degradation Pathway; Enzymes; Excision; Farnesol; Funding; Homologous Gene; Hydroxymethylglutaryl-CoA reductase; In Vitro; Integral Membrane Protein; Isoenzymes; Learning; Ligase; Lipids; Localized; Mediating; Mediator of activation protein; Medical; Membrane; Modeling; Pathway interactions; Play; Process; Proteins; Quality Control; Rate; Regulation; Role; Signal Pathway; Signal Transduction; Signaling Molecule; Sterols; Structure; Techniques; Testing; Time; Transmembrane Domain; Ubiquitin; Ubiquitination; Work; Yeasts; in vitro Assay; insight; novel strategies; programs; protein degradation; protein misfolding; response; ubiquitin ligase; ubiquitin-protein ligase

DESCRIPTION (provided by applicant): HMG-CoA reductase (HMGR) is the rate-limiting enzyme of sterol synthesis. HMGR is an integral membrane protein that undergoes regulated degradation by ER-associated degradation, or ERAD, in response to changing cellular demand for sterols. We originally showed that the yeast HMGR isozyme Hmg2p is regulated in a manner similar to the mammalian enzyme, allowing us to exploit unique study opportunities available in yeast. Hmg2p undergoes degradation by the HRD pathway, through the action of the Hrdlp E3 ubiquitin ligase, and the sterol pathway molecule FPP regulates HRD-dependent Hmg2p degradation. The HRD pathway also functions in ER quality control, programming the destruction of many misfolded ER proteins. Accordingly, we have proposed the structural transition hypothesis for regulation: that an FPP-derived signal causes Hmg2p to undergo transition to a structure with features of a HRD quality control substrate. We have been testing this model and at the same time increasing our understanding of the HRD pathway, developing several new biochemical assays to directly address these issues. In the current work we will 1) Continue our analysis of the HRD ubiquitin ligase complex, 2) Analyze the features of the Hmg2p protein that allow its regulation by sterol pathway signals, 3) Delineate the identity and action of the lipid signals that control Hmg2p entry into the HRD pathway. 4) Study the mechanism of retrotranslocation of HRD pathway substrates required for ERAD of Hmg2p. Hmg2p degradation lies at the interface of sterol regulation and protein quality control. Thus, our work is relevant both to understanding the cellular control of sterol synthesis, and the destruction of misfolded proteins; two areas of broad and current medical import.

描述（申请人提供）：HMGR - coa还原酶（HMGR）是固醇合成的限速酶。HMGR是一种完整的膜蛋白，它通过内质网相关降解（ERAD）进行调节降解，以响应细胞对固醇需求的变化。我们最初发现酵母HMGR同工酶Hmg2p以一种类似于哺乳动物酶的方式调节，这使我们能够利用酵母中可用的独特研究机会。Hmg2p通过HRD途径降解，通过Hrdlp E3泛素连接酶的作用，而甾醇途径分子FPP调节HRD依赖性Hmg2p降解。HRD通路也在内质网质量控制中起作用，对许多错误折叠的内质网蛋白的破坏进行编程。因此，我们提出了调控的结构转变假说：fpp衍生的信号导致Hmg2p转变为具有HRD质量控制基板特征的结构。我们一直在测试这个模型，同时增加我们对HRD途径的理解，开发了几种新的生化分析方法来直接解决这些问题。在目前的工作中，我们将1)继续我们对HRD泛素连接酶复合物的分析，2)分析Hmg2p蛋白允许其通过固醇途径信号调节的特征，3)描述控制Hmg2p进入HRD途径的脂质信号的身份和作用。4)研究Hmg2p ERAD所需的HRD通路底物的逆转录易位机制。Hmg2p的降解处于固醇调节和蛋白质质量控制的界面。因此，我们的工作与理解细胞对固醇合成的控制和错误折叠蛋白质的破坏有关；两个具有广泛和当前医学意义的领域。