Rewiring Phospholipid Biosynthesis Reveals Resilience to Membrane Perturbations

The organelles of eukaryotic cells differ in their membrane lipid composition. This heterogeneity is achieved by the localization of lipid synthesizing and modifying enzymes to specific compartments, as well as by intracellular lipid transport that utilizes vesicular and non-vesicular routes to ferry lipids from their place of synthesis to their destination. For instance, the major and essential phospholipids, phosphatidylethanolamine (PE) and phosphatidylcholine (PC) can be produced by multiple pathways and, in the case of PE, also at multiple locations. However, the molecular components that underlie lipid homeostasis as well as the routes allowing their distribution remain unclear. Here, we present an approach in which we simplify and rewire yeast phospholipid synthesis by redirecting PE and PC synthesis reactions to distinct subcellular locations using chimeric enzymes fused to specific organelle targeting motifs. In rewired conditions, viability is expected to depend on homeostatic adaptation to the ensuing lipostatic perturbations and on efficient interorganelle lipid transport. We therefore performed genetic screens to identify factors involved in both of these processes.

真核细胞的细胞器在膜脂组成上存在显著差异。这种组成异质性可通过两种途径实现：一是将脂质合成与修饰酶定位于特定细胞区室，二是借助囊泡与非囊泡运输途径的细胞内脂质转运系统，将脂质从合成位点运送至其发挥功能的目的地。例如，作为主要且必需的磷脂，磷脂酰乙醇胺（phosphatidylethanolamine, PE）与磷脂酰胆碱（phosphatidylcholine, PC）可通过多条通路合成，而就PE而言，其合成位点也并非单一。然而，支撑脂质稳态以及介导脂质分布的分子机制与途径仍未完全阐明。本研究提出一种研究策略：通过将融合了特定细胞器靶向基序的嵌合酶重新导向不同亚细胞位置，以此简化并重塑酵母的磷脂合成通路。在经过重塑的培养条件下，酵母细胞的存活将依赖于对随之而来的脂质稳态扰动的适应性调节，以及高效的细胞器间脂质运输过程。因此，我们开展了遗传筛选实验，以鉴定参与这两类过程的关键功能因子。