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

• Applicants: Professorin Dr. Suzanne Eaton (†); Professor Dr. Hans-Joachim Knölker; Dr. Teymuras Kurzchalia
• Subject Area: Biochemistry
• Term: from 2009 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 128165215

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.

• DFG Programme: Research Grants