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

项目摘要/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。一场激动人心的 近年来的发展是认识到脂平衡对蛋白质质量控制至关重要。 未折叠蛋白反应(UPR)感知内质网中错误折叠的蛋白质并协调 一个广泛的细胞重塑计划来应对这一威胁。脂类代谢的各种缺陷会引发 UPR，而UPR反过来又控制一些脂代谢基因的表达。此外，与 错误折叠蛋白质的经典管腔信号机制，最近的工作表明存在第二个 检测内质网膜缺陷的传感器通路(“双层应力”)。的功能特性 膜(如厚度、流动性、曲率)在很大程度上取决于它们的组成。一点也不早 膜是静态或惰性结构的概念，我们现在理解膜是高度动态的 并且能够响应于变化的细胞条件/需求来改变它们的组成。这项建议 重点关注一组知之甚少的脂类，称为超长链脂肪酸(VLCFA)，它相对 数量不多，但起关键作用的。我们假设VLCFAs在蛋白质质量控制中起着关键作用 和膜的动态平衡。为了抑制VLCFA的利用，我们研究了主要VLCFA CoA的一个突变体 合成酶，脂肪1。我们的初步数据表明，Fat1在内质网稳态中起着重要作用，它的丢失 触发UPR的补偿性感应。为了了解这种效应的基础，我们进行了一项 基于光谱分析的脂肪组学分析。值得注意的是，FAT1Δ突变体的细胞膜显著增加。 饱和度，这是UPR的已知诱因。这种影响至少部分是通过部分功能丧失来实现的。 在Ole1中，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 调节膜动态平衡和UPR。最近的数据表明膜饱和度是一个关键的决定因素 阿尔法-突触核蛋白毒性，这是导致帕金森氏症的原因。我们的数据表明Fat1是一种 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的监管机制 酵母和果蝇中的突触核蛋白毒性。这项提案的完成预计将提供基本和 以疾病为导向的机制洞察这一新兴但基本的细胞生物学领域。

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.