Abstract
Lipids orchestrate biological processes by acting remotely as signaling molecules or locally as membrane components that modulate protein function. Detailed insight into lipid function requires knowledge of the subcellular localization of individual lipids. We report an analysis of the subcellular lipidome of the mammalian macrophage, a cell type that plays key roles in inflammation, immune responses, and phagocytosis. Nuclei, mitochondria, endoplasmic reticulum (ER), plasmalemma, and cytoplasm were isolated from RAW 264.7 macrophages in basal and activated states. Subsequent lipidomic analyses of major membrane lipid categories identified 229 individual/isobaric species, including 163 glycerophospholipids, 48 sphingolipids, 13 sterols, and 5 prenols. Major subcellular compartments exhibited substantially divergent glycerophospholipid profiles. Activation of macrophages by the Toll-like receptor 4-specific lipopolysaccharide Kdo(2)-lipid A caused significant remodeling of the subcellular lipidome. Some changes in lipid composition occurred in all compartments (e.g., increases in the levels of ceramides and the cholesterol precursors desmosterol and lanosterol). Other changes were manifest in specific organelles. For example, oxidized sterols increased and unsaturated cardiolipins decreased in mitochondria, whereas unsaturated ether-linked phosphatidylethanolamines decreased in the ER. We speculate that these changes may reflect mitochondrial oxidative stress and the release of arachidonic acid from the ER in response to cell activation.
Highlights
Lipids orchestrate biological processes by acting remotely as signaling molecules or locally as membrane components that modulate protein function
Because the physical properties of individual membranes are determined by lipid head groups and by their acyl chain composition [6, 8], we sought to overcome these limitations by combining subcellular fractionation approaches we developed for the macrophage [9] with sophisticated mass spectrometric analysis of lipid species
We choose to not include the two lipid categories that contain relatively hydrophilic and extremely hydrophobic lipids. Hydrophilic lipids such as eicosanoids, sphingoid bases, and their phosphates and fatty acids were excluded from analysis, because these lipids are expected to be very released from membranes of origin and are likely to redistribute during extensive subcellular fractionation
Summary
Lipids orchestrate biological processes by acting remotely as signaling molecules or locally as membrane components that modulate protein function. Oxidized sterols increased and unsaturated cardiolipins decreased in mitochondria, whereas unsaturated ether-linked phosphatidylethanolamines decreased in the ER We speculate that these changes may reflect mitochondrial oxidative stress and the release of arachidonic acid from the ER in response to cell activation.—Andreyev, A. Journal of Lipid Research Volume 51, 2010 2785 cells or tissues followed by separation and measurement of lipid classes and subclasses When these approaches are taken, information regarding the subcellular distribution of lipid classes and the molecular identity of individual species of lipids is lost. In choosing a cell to apply these approaches to, we took advantage of the extraordinary biology of the macrophage This cell type is ubiquitous throughout the mammalian kingdom and undergoes drastic transformation in response to activation [10,11,12,13]. The LIPID MAPS Consortium has developed quantitative methods for comprehensively evaluating the composition, biosynthesis, and function of macrophage lipids [14] and has applied these methods to subcellular fractions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
