Lipid map of the mammalian cell

Technological developments, especially in mass spectrometry and bioinformatics, have revealed that living cells contain thousands rather than dozens of different lipids [for classification and nomenclature, see Fahy et al. (Fahy et al., 2009)]. Now, the resulting questions are what is the relevance of each of these unique molecules for the cell and how do cells use lipids for their vital functions? The answer requires an integrative approach – cellular lipidomics – which addresses first the distribution of all lipids between the various organelle membranes and then their local organization within each membrane. To understand lipid homeostasis and its dynamics, one has to study the localized metabolism of lipids, their transport within and between the various membranes, and the sensors and effectors that govern these processes. In terms of function, above all, we need to understand the physical behavior of complex lipid mixtures and their effect on local protein structure, organization and function. Finally, in the course of evolution, many lipids and lipid metabolites have acquired key functions in the signaling networks that wire the cell, by binding to cognate receptors and by recruiting proteins to specific membranes. The accompanying poster describes the lipid content of the various organelle membranes, illustrates lipid localization and dynamics in various subcellular locations, and explains the structure of lipids and their biosynthetic pathways. Below, we highlight additional issues that are important in lipid cell biology, and aim to provide a framework and a timely update for lipid systems biology.