Review Ceramide: From lateral segregation to mechanical stress Iván López-Montero a, ⁎, Francisco Monroy a , Marisela Vélez b,c , Philippe F. Devaux d a Universidad Complutense de Madrid, Madrid, Spain b Instituto de Catálisis y Petroleoquímica, CSIC, Madrid, Spain c IMDEA Nanociencias, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain d Institut de Biologie Physico-Chimique, Paris, France abstract article info Article history: Received 8 September 2009 Received in revised form 25 November 2009 Accepted 9 December 2009 Available online 21 December 2009 Keywords: Ceramide Sphingomyelinase Mechanical stress Lipid domains Ceramide is a sphingolipid present in eukaryotic cells that laterally segregates into solid domains in model lipid membranes. Imaging has provided a wealth of structural information useful to understand some of the physical properties of these domains. In biological membranes, ceramide is formed on one of the membrane leaflets by enzymatic cleavage of sphyngomyelin. Ceramide, with a smaller head size than its parent compound sphyngomyelin, induces an asymmetric membrane tension and segregates into highly ordered domains that have a much high shear viscosity than that of the surrounding lipids. These physical properties, together with the rapid transmembrane flip-flop of the locally produced ceramide, trigger a sequence of membrane perturbations that could explain the molecular mechanism by which ceramide mediates different cell responses. In this review we will try to establish a connection between the physical membrane transformations in model systems known to occur upon ceramide formation and some physiologically relevant process in which ceramide is known to participate. © 2009 Elsevier B.V. All rights reserved. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1349 2. Beyond ceramide-domain imaging in model membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1349 2.1. Ceramide-containing membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1349 2.1.1. Lateral phase behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1349 2.1.2. Visualising protein sorting in ceramide-rich domains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1351 2.1.3. Measuring flip-flop rates and detergent resistance through optical imaging . . . . . . . . . . . . . . . . . . . . . . . . 1351 2.1.4. Mechanical properties of ceramide-enriched domains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1351 2.2. Ceramide enzymatic conversion in SM-containing membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1351 2.2.1. Lateral phase behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1351 2.2.2. Domain clustering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1352 2.2.3. Mechanical stress: vesicle aggregation, budding, rupture, membrane defects and content efflux . . . . . . . . . . . . . . 1352 3. Ceramide and SMase enzymatic activity: a perfect marriage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1352 3.1. Compression elasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1353 3.2. Shear viscoelasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1353 3.3. Curvature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1353 3.4. Lamellar to hexagonal phase transition and lipid scrambling promotion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1353 3.5. Surface tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1353 4. Effects of ceramide generation on cells: a biophysical viewpoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1354 4.1. Clustering and capping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1354 4.2. Blebbing and lipid scrambling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1354 Biochimica et Biophysica Acta 1798 (2010) 1348–1356 Abbreviations: Chol, cholesterol; Cer, ceramide; C2Cer, acetoyl-Cer; C6Cer, hexanoyl-Cer; C8Cer, octanoyl-Cer; C10Cer, decanoyl-Cer; C12Cer, lauroyl-Cer; C14Cer, myristoyl-Cer; C16Cer, palmitoyl-Cer; C18Cer, stearoyl-Cer; C20Cer, arachidoyl-Cer; C24Cer, lignoceroyl-Cer; C24:1Cer, nervonoyl-Cer; ECer, Egg-Cer; PC, phosphatidylcholine; DMPC, 1,2- dimyristoyl-PC; DPPC, dipalmitoyl-PC; POPC, 1-palmitoyl-2-oleoyl-PC; DOPC, 1,2-dioleoyl-PC; SOPC, 1-stearoyl-1-oleyl-PC; EPC, Egg-PC; SM, sphingomyelin; C16SM, palmitoyl-SM; C18SM, stearoyl-SM; ESM, Egg-SM; BSM, brain-SM; PE, phosphatidyl ethanolamine; DPPE, dipalmitoyl-PE; DOPE, 1,2-dioleoyl-PE; EPE, Egg-PE; L o , liquid-ordered phase; L d , liquid- disordered phase; L β , solid phase; Smase, sphingomyelinase; AFM, atomic force microscopy; FCS, fluorescence correlation spectroscopy; GUV, giant unilamellar vesicle; FITC, fluorescein isothiocyanate; Cy3, cyanine 3 ⁎ Corresponding author. E-mail address: ivanlopez@quim.ucm.es (I. López-Montero). 0005-2736/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.bbamem.2009.12.007 Contents lists available at ScienceDirect Biochimica et Biophysica Acta journal homepage: www.elsevier.com/locate/bbamem