The 58th Annual Meeting and Symposium of the Society of General Physiologists Lipid Signaling in Physiology

By virtue of the strength of hydrophobic interactions and the malleability of phospholipid acyl chains, membrane lipids become one of the important glues of life. The liquid-crystalline organization of the bilayer component of biological membranes enables the membranes to be effective, cohesive, and yet flexible, barriers separating two fluid compartments. Integral membrane proteins are imbedded into the bilayer, where they catalyze the selective transfer of information and material between the two compartments. Hydrophobic interactions between the proteins' bilayer-spanning domains and the bilayer lipids cause the lipids to pack tightly around the proteins, thereby maintaining the barrier properties. Because the bilayer lipids are organized as a liquid-crystalline sheet, the flexible lipids will accommodate protein conformational changes that involve the protein/bilayer boundary. Individual lipid molecules also may be imbedded at protein–protein interfaces where they not only may " plug " potential leaks but also stabilize supramolecular assemblies of bilayer-spanning proteins. Lipid bilayers, however, are not just thin sheets of liquid hydrocarbon, stabilized by the lipids' polar head groups, which serve as " solvents " for the bilayer-spanning proteins. Some polar head groups serve as ligands that bind to specific protein domains, and some head groups carry a net negative charge that in a less specific manner attract positively charged protein domains to the membrane/solution interface, where their adsorp-tion/binding may be stabilized by hydrophobic interactions. The polar head groups thus serve to direct and organize protein targeting to different plasma and organellar membrane/solution interfaces. This means that even though membrane lipids possess no intrinsic catalytic activity, they become key participants in the regulation of membrane turnover and cell metabolism, a regulation that becomes exquisite due to the regulated turnover of membrane lipids. Lipid bilayers also are material bodies with well-defined elastic moduli, such that bilayer perturbations caused by membrane protein conformational changes involving the protein/bilayer boundary will incur an energetic cost. The hydrophobic cohesion between bilayer-spanning proteins and the host bilayer therefore couples the energetics of membrane protein con-formational changes to the associated bilayer perturbation energy, which provides for additional mechanisms by which membrane lipids regulate biological function. Recently, the importance of membrane lipids for many different physiological processes was highlightedsity School of Medicine organized the symposium on Lipid Signaling in Physiology, which highlighted the recent progress that has taken place in understanding the physiological importance of membrane lipids for cell signaling, membrane turnover, and membrane protein function. With 164 participants and 104 …