Endoplasmic reticulum-assisted mitochondrial precursor biogenesis and quality control

内质网辅助线粒体前体生物发生和质量控制

• 批准号: 10748025
• 负责人: Steven Michael Claypool
• 金额: $ 33.28万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-15 至 2027-06-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10748025
• 关键词: ATP phosphohydrolase; Biogenesis; Biological Process; Biology; Carboxy-Lyases; Cells; Cellular Stress; Chronology; Client; Complex; Destinations; Detection; Disease; Endoplasmic Reticulum; Excision; Goals; Health; Heat shock proteins; Human; Inner mitochondrial membrane; Knowledge; Life; Link; Lipids; Mediating; Membrane; Mitochondria; Mitochondrial Membrane Protein; Mitochondrial Proteins; Modeling; Molecular; Molecular Chaperones; Nuclear; Organelles; Outer Mitochondrial Membrane; Pathway interactions; Phosphatidylethanolamine; Phosphatidylserines; Phospholipid Metabolism; Phospholipids; Process; Protein Import; Proteins; Publishing; Quality Control; Resolution; Retrieval; Role; Staging; Stress; Surface; System; Testing; Ubiquitin; Yeasts; coping; glycosylation; insight; interest; multicatalytic endopeptidase complex; mutant; novel; operation; protein degradation; trafficking; translocase; virtual

Over the past decade, roles for the endoplasmic reticulum (ER) in the biogenesis of select nuclear-encoded mitochondrial precursors and the degradation of mutant, mis-localized, or non-productively imported proteins from the mitochondrial outer membrane (OM) have begun to emerge. Our interest in this unanticipated, novel ER-associated mitochondrial biology was serendipitous. In our ongoing efforts to characterize the lipid substrate trafficking requirements for phosphatidylserine (PS) decarboxylase 1 (Psd1 in yeast, PISD in humans), an evolutionarily conserved, integral inner mitochondrial membrane protein that produces phosphatidylethanolamine (PE), it became a priority for us to independently ascertain if a small fraction of wild type (WT) Psd1 is glycosylated and thus targeted to the endomembrane system, as recently claimed. Our generated results support the unavoidable conclusion that in yeast, the vast majority, if not all, of functional Psd1 is mitochondrially localized. However, we did uncover an intimate relationship between Psd1 and the ER: unlike the WT protein, non-functional forms of Psd1 are dually localized to the ER, where they are glycosylated, ubiquitinated, and rapidly degraded. Given the role of the ER as a staging ground for the efficient removal of non-functional Psd1, we then asked two questions ― 1) Is Psd1 biogenesis supported by a recently discovered Djp1-mediated Endoplasmic Reticulum Surface Retrieval pathway (ER-SURF)? and 2) Does the accumulation of ER-associated non-functional Psd1 depend on Msp1, an outer mitochondrial membrane resident AAA-ATPase known to remove mis-targeted proteins and non-productively imported mitochondrial precursors from the outer membrane? The resulting answers establish the premise for our proposed aims and identify Psd1 as an ideal model substrate to define novel mechanisms of ER-SURF and protein degradation that will undoubtedly apply to other mitochondrial proteins. The goal of Aim 1 is to define the early, pre- mitochondrial steps of Psd1 biogenesis that are mediated by specific interactions that occur at the ER. Other than a critical role for the Hsp40 cochaperone, Djp1, virtually nothing is known about ER-SURF. Results from Aim 1 will provide mechanistic insight about mitochondrial targeting through this novel pathway and whether it can be coerced in specific contexts to support non-mitochondrial biology. Over the past seven years, it has become increasingly appreciated that the accumulation of mitochondrial precursors outside of this organelle activates a range of cellular stress responses. In this context, our discovery that non-functional mutant Psd1 temporarily associates with ER membranes prior to being degraded is particularly exciting. The goal of Aim 2 is to determine the molecular mechanisms of non-functional Psd1 resolution. Results from Aim 2 will transform our understanding of how cells cope with mitochondrial precursors that fail to reach their correct destination, an emerging focus in the field.

在过去的十年中，内质网（ER）在选择核编码生物发生中的作用 线粒体前体和突变、错误定位或非生产性进口蛋白质的降解 来自线粒体外膜（OM）的细胞已经开始出现我们对这种意想不到的新颖的兴趣。 在我们不断努力表征脂质的过程中，与内质网相关的线粒体生物学是偶然的。 磷脂酰丝氨酸 (PS) 脱羧酶 1（酵母中的 Psd1，酵母中的 PISD）的底物运输要求 人类），一种进化上保守的完整线粒体内膜蛋白，可产生 磷脂酰乙醇胺（PE），独立确定是否有一小部分野生动物成为我们的首要任务 正如我们最近声称的那样，（WT）型 Psd1 被糖基化，因此靶向内膜系统。 生成的结果支持了不可避免的结论，即在酵母中，绝大多数（如果不是全部）功能性 Psd1 是线粒体定位的，但是我们确实发现了 Psd1 和 ER 之间的密切关系： 与 WT 蛋白不同，Psd1 的非功能形式双重定位于 ER，它们位于 考虑到内质网作为高效物质中转站的作用，糖基化、泛素化和快速降解。 去除非功能性的 Psd1，然后我们问了两个问题 ― 1) Psd1 的生物发生是否得到了最近的研究的支持？ 发现了 Djp1 介导的内质网表面修复途径 (ER-SURF) 和 2) ER 相关的非功能性 Psd1 的积累取决于线粒体外膜 Msp1 已知常驻 AAA-ATP 酶可去除错误靶向的蛋白质和非生产性导入的线粒体 由此产生的答案为我们提出的目标奠定了前提 确定 Psd1 作为定义 ER-SURF 和蛋白质降解新机制的理想模型底物 这无疑适用于其他线粒体蛋白。目标 1 的目标是定义早期的、预-的。 Psd1 生物发生的线粒体步骤由 ER 其他发生的特定相互作用介导。 除了 Hsp40 辅助伴侣 Djp1 的关键作用之外，我们对 ER-SURF 的结果几乎一无所知。 目标 1 将通过这一新途径提供有关线粒体靶向的机制见解，以及它是否 在过去的七年里，它已经在特定的环境中被强制支持非线粒体生物学。 人们越来越认识到线粒体前体在该细胞器之外的积累 在此背景下，我们发现非功能性突变体 Psd1 会激活一系列细胞应激反应。 在降解之前与 ER 膜暂时结合是特别令人兴奋的目标 2。 确定非功能性 Psd1 分辨率的分子机制将改变目标 2 的结果。 我们对细胞如何应对未能到达正确目的地的线粒体前体的理解， 该领域的新兴焦点。