A New Cellular Protein Degradation Pathway for Lysosome Homeostasis and Remodeling

虽然他们可能没有意识到，但至少从细胞生物学家的角度来看，每个人都在循环利用以维持地球上的生命。这是因为所有的真核细胞，包括那些构成你和我的细胞，都依赖于一种叫做溶酶体的细胞器来回收生物材料。溶酶体回收不需要的或受损的细胞成分，并通过将细胞外碎片或病原体转化为重要的营养来源来清除它们。因此，当细胞饥饿时，需要溶酶体的活性来维持新陈代谢，并清除细胞老化时积累的有毒生物物质。为了发挥作用，这些动态细胞器依靠营养转运体将分解代谢产物（氨基酸、脂质、核酸）返回细胞以供再利用。但人们对这些转运蛋白知之甚少，包括它们是如何被调节或降解的。直到最近，当我们在模式生物酿酒酵母中发现了一个新的过程，称为al - enal片段（ILF）途径，该途径在受损时选择性地降解溶酶体转运体，响应底物水平，或通过tor信号传导细胞衰老的重要介质。这一过程选择性地将转运蛋白分类到一个膜区域，在同型溶酶体膜融合时被内化并被管腔水解酶降解。但是，要全面理解这个新过程及其对细胞生理学的贡献，必须回答许多悬而未决的问题：转运蛋白是如何被标记和分类以进行降解的？它会在其他聚变事件中发生吗？ILF通路能降解表面多面体蛋白吗？它有助于长寿吗？这个通路在后生动物中是否保守？主要使用酿酒酵母及其液泡溶酶体作为模型，我将完成五个目标来回答这些问题，并实现我的目标，了解ILF途径的分子基础，其生理学以及它如何促进真核细胞的寿命。这个雄心勃勃的系列研究将在5年内由1名博士后、3名研究生和1名本科生组成，他们将掌握遗传学、显微镜学、生物化学和细胞生物学的前沿方法——这是学术界和工业界追求职业所需的理想技能。我们预计，对于溶酶体来说，ILF通路将与TOR-和tfeb信号通路同样重要，通过它重塑膜以适应细胞代谢和其他生物学的变化，类似于通过内吞作用重塑质膜的重要性，这是多种生理学的基础。预期的结果也将有助于揭示大自然圣杯的秘密，未来的工作将把这些最先进的知识转化为延长寿命的应用，支持加拿大知识产权和相关生物技术的发展。

Although they may not be aware, everyone recycles to sustain life on earth at least from the perspective of a cell biologist. This is because all eukaryotic cells, including those that constitute you and I, rely on organelles called lysosomes to recycle biomaterials. Lysosomes recycle unneeded or damaged cellular components, and clear extracellular debris or pathogens by converting them into an important source of nutrients. As such, lysosome activity is needed to sustain metabolism when cells are starved, and to remove toxic biomaterials that accumulate in cells as they age. To function, these dynamic organelles rely on nutrient transporters to return products of catabolism (amino acids, lipids, nucleic acids) to the cell for reuse. But little is know about these transporters including how they are regulated or degraded. Until recently, when we discovered a new process in the model organism Saccharomyces cerevisiae called the IntraLumenal Fragment (ILF) pathway that selectively degrades lysosome transporters when damaged, in response to substrate levels, or by TOR-signaling an important mediator of cellular aging. This process selectively sorts transporters into an area of membrane that is internalized and degraded by lumenal hydrolases upon homotypic lysosome membrane fusion. But many open questions must be answered to comprehensively understand this novel process and its contribution(s) to cell physiology: How are transporters labeled and sorted for degradation? Does it occur during other fusion events? Can the ILF pathway degrade surface polytopic proteins? Does it contribute to longevity? Is this pathway conserved in metazoans? Primarily using S. cerevisiae and its vacuolar lysosome as models, I will complete five objectives to answer these questions and achieve my goal of understanding the molecular underpinnings of the ILF pathway, its physiology and how it may promote longevity in eukaryotic cells. This ambitious series of studies will be completed within 5 years by a motivated team of 1 postdoctoral fellow, 3 graduate students and an undergraduate student who will master cutting-edge methods in genetics, microscopy, biochemistry and cell biology - desirable skills needed to pursue careers in academia and industry. We anticipate that the ILF pathway will be equally critical to lysosomes as TOR- and TFEB-signaling, whereby it remodels membranes to accommodate changes in cell metabolism and other biology, akin to the importance of plasma membrane remodeling by endocytosis that underlies diverse physiology. Anticipated results will also help reveal the secret of nature's holy grail, and future work will translate this state-of-the-art knowledge into applications to prolong longevity, supporting development of intellectual property and related biotechnologies in Canada.