Lipid Specific - Molecular Determinants of Sterol-Sphingolipid-Protein Interactions in Living Cells and Organisms

硬脂酸和鞘脂是质膜和内吞途径的主要脂质，几乎仅在真核生物中发现，并且在物种之间其特定结构不同。它们调节膜流动性，并已被提出参与膜微区的形成，称为胆固醇鞘脂筏，这可能在一些膜相关蛋白的定位和/或活性中发挥作用。虽然脂筏的概念与模型和细胞膜的许多发现一致，但这一假设不足以解释生物学上观察到的甾醇和鞘脂结构之间的相互依赖性，也无助于预测哪些特定的蛋白质-脂质相互作用可能在细胞和组织水平上调节功能。我们建议，许多属性归因于脂筏依赖于直接的蛋白质-脂质相互作用，而不是一般的膜特性，如流动性和秩序。控制细胞膜中特定甾醇-鞘脂-蛋白质相互作用的分子决定因素不能从模型膜的研究中预测，其中生物膜的结构复杂性不能准确地重建。我们建议，而不是使用实验上可行的模式生物（酵母，苍蝇和蠕虫）作为平台，以确定关键的结构要素和功能的后果甾醇-鞘脂-蛋白质相互作用。在哺乳动物细胞和组织中的平行研究将集中在与人类生理学和病理学相关的问题中甾醇-鞘脂-蛋白质亲和力的选定方面。我们将采用最先进技术的广泛组合，包括遗传学，系统生物表型，甾醇和鞘脂的化学合成，活细胞/组织中的脂质成像，以及用于脂质分析的质谱法。我们希望确定哪种甾醇、鞘脂或甾醇-鞘脂对具有特定的功能，设计原理来预测新的对，并在几个实验系统中测试它们。在一个模式生物中进行的工作应该提供有关特定蛋白质-脂质相互作用原理的信息，这些信息可以在其他系统中进行测试。

Sterols and sphingolipids are major lipids of the plasma membrane and endocytic pathways found almost exclusively in eucaryotes and differ in their specific structure between species. They regulate membrane fluidity and have been proposed to participate in the formation of membrane microdomains, termed cholesterol-sphingolipid rafts, which may play a role in the localization and/or activity of some membrane-associated proteins. While the concept of lipid rafts is consistent with a number of findings from model and cell membranes, this hypothesis is not sufficient to explain the biologically observed interdependence between sterol and sphingolipid structures, nor does it help to predict which specific protein-lipid interactions may regulate functions at the cell and tissue level. We propose that many properties ascribed to lipid rafts depend on direct protein-lipid interactions rather than general membrane properties, such as fluidity and order. The molecular determinants governing specific sterol-sphingolipid-protein interactions in cell membranes cannot be predicted from studies in model membranes, where the structural complexity of biomembranes cannot be accurately reconstituted. We propose to use instead experimentally amenable model organisms (yeast, flies and worms) as platforms to identify key structural elements and functional consequences of sterol-sphingolipid-protein interactions. Parallel studies in mammalian cells and tissues will focus on selected aspects of sterol-sphingolipid-protein affinities in questions relevant for human physiology and pathology. We will employ a wide combination of state-of-the-art techniques, including genetics, systematic biological phenotyping, chemical synthesis of sterols and sphingolipids, lipid imaging in living cells/tissues, and mass spectrometry for lipid analysis. We wish to determine which sterol(s), sphingolipid(s) or sterol-sphingolipid pairs work for a particular function, design principles to make predictions for new pairs and test them in several experimental systems. Work carried out in one model organism should provide information regarding principles of specific protein-lipid interactions that can be tested in other systems.