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

甾醇和鞘磷脂是质膜和内吞途径的主要脂类，几乎仅存在于真核生物中，它们的特殊结构在物种之间存在差异。它们调节细胞膜的流动性，并被认为参与了膜微域的形成，称为胆固醇鞘脂筏，这可能在某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一些发现是一致的，但这一假说不足以解释在生物学上观察到的甾醇和鞘脂结构之间的相互依赖，也不有助于预测哪些特定的蛋白质-脂类相互作用可能调节细胞和组织水平的功能。我们认为，脂筏的许多性质依赖于直接的蛋白质-脂类相互作用，而不是一般的膜性质，如流动性和有序性。控制细胞膜中特定的甾醇-鞘糖脂-蛋白质相互作用的分子决定因素不能通过模型膜的研究来预测，在模型膜中，生物膜的结构复杂性不能被准确地重建。相反，我们建议使用实验上可服从的模型生物(酵母、苍蝇和蠕虫)作为平台，以确定甾醇-鞘磷脂-蛋白质相互作用的关键结构元素和功能后果。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-鞘磷脂-蛋白质亲和力的选定方面。我们将广泛使用最先进的技术组合，包括遗传学、系统生物表型、甾醇和鞘磷脂的化学合成、活细胞/组织中的脂肪成像，以及用于脂肪分析的质谱学。我们希望确定哪一种甾醇(S)、鞘脂(S)或甾醇-鞘磷脂对对特定功能起作用，设计原则来预测新的对，并在几个实验系统中进行测试。在一个模型生物体中进行的工作应该提供关于特定蛋白质-脂肪相互作用的原理的信息，这些原理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.