Role of very long chain fatty acids in protein quality control and membrane homeostasis

项目概要/摘要 细胞已经产生了复杂的应激反应来识别和消除错误折叠的蛋白质。令人兴奋的 近年来的发展已经认识到脂质稳态对于蛋白质质量控制至关重要。 未折叠蛋白质反应 (UPR) 感知内质网中错误折叠的蛋白质并协调 一项广泛的细胞重塑计划来应对这一威胁。脂质代谢的各种缺陷会引发 UPR，而UPR又控制一些脂质代谢基因的表达。此外，与 错误折叠蛋白质的典型管腔信号传导机制，最近的工作表明存在第二个 检测 ER 膜缺陷（“双层应力”）的传感器通路。的功能特性 膜（例如厚度、流动性、曲率）很大程度上取决于其成分。远非早 膜作为静态或惰性结构的概念，我们现在了解到膜是高度动态的 并能够改变其组成以响应不断变化的细胞条件/需求。这个提议 重点关注一组人们知之甚少的脂质，称为极长链脂肪酸 (VLCFA)，它们相对来说 数量不多但执行关键功能。我们假设 VLCFA 在蛋白质质量控制中发挥关键作用 和膜稳态。为了抑制 VLCFA 的利用，我们研究了主要 VLCFA CoA 的突变体 合成酶，脂肪1。我们的初步数据表明 Fat1 在 ER 稳态中发挥着重要作用，并且它的丢失 触发 UPR 的补偿性诱导。为了了解这种效应的基础，我们进行了大规模 基于光谱测定的脂质组学分析。值得注意的是，fat1Δ突变体表现出膜的显着增加 饱和度是 UPR 的已知诱导剂。这种效应至少部分是通过部分功能丧失来介导的 Ole1，酵母中唯一的脂肪酰基去饱和酶。在目标 1 中，我们将确定 VLCFA 的机制 调节膜稳态和 UPR。最近的数据表明膜饱和度是一个关键决定因素 α-突触核蛋白毒性，这是导致帕金森病的原因。我们的数据表明 Fat1 是 突触核蛋白毒性的重要调节因子。在目标 2 中，我们将确定 VLCFA 的调节机制 突触核蛋白对酵母和果蝇的毒性。预计该提案的完成将提供基本和 以疾病为导向的机制洞察细胞生物学这一新兴但基本的领域。

Project Summary/Abstract Cells have developed complex stress responses to identify and eliminate misfolded proteins. An exciting development in recent years has been the recognition that lipid homeostasis is critical for protein quality control. The Unfolded Protein Response (UPR) senses misfolded proteins in the endoplasmic reticulum and orchestrates a broad program of cellular remodeling to address this threat. Various defects in lipid metabolism trigger the UPR, and the UPR in turn controls the expression of some lipid metabolic genes. Furthermore, in contrast to the canonical luminal signaling mechanism for misfolded proteins, recent work indicates the presence of a second sensor pathway that detects defects in the ER membrane ("bilayer stress"). The functional properties of membranes (e.g. thickness, fluidity, curvature) are largely determined by their compositions. Far from early conceptions of membranes as static or inert structures, we now understand that membranes are highly dynamic and capable of altering their compositions in response to changing cellular conditions/needs. This proposal focuses on a poorly understood group of lipids known as very long chain fatty acids (VLCFAs) which are relatively unabundant but perform critical functions. We hypothesize that VLCFAs play key roles in protein quality control and membrane homeostasis. To inhibit VLCFA utilization, we have studied a mutant of the major VLCFA CoA synthetase, Fat1. Our preliminary data indicate that Fat1 plays an important role in ER homeostasis, and its loss triggers compensatory induction of the UPR. To understand the basis for this effect, we carried out a mass spectrometry-based lipidomic analysis. Remarkably, the fat1Δ mutant showed a dramatic increase in membrane saturation which is a known inducer of the UPR. This effect is mediated, at least in part, via partial loss of function of Ole1, the sole fatty acyl desaturase in yeast. In Aim 1, we will determine the mechanism by which VLCFAs regulate membrane homeostasis and the UPR. Recent data implicate membrane saturation as a key determinant of alpha-synuclein toxicity, which is responsible for Parkinson's disease. Our data indicate that Fat1 is an important regulator of synuclein toxicity. In Aim 2, we will determine mechanism by which VLCFAs regulate synuclein toxicity in yeast and Drosophila. Completion of this proposal is expected to provide both basic and disease-oriented mechanistic insight into this emerging but fundamental area of cell biology.