This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Crane, J. M. Articles by Tamm, L. K. Search for Related Content PubMed PubMed Citation Articles by Crane, J. M. Articles by Tamm, L. K.

Role of Cholesterol in the Formation and Nature of Lipid Rafts in Planar and Spherical Model Membranes

Department of Molecular Physiology and Biological Physics and Biophysics Program, University of Virginia, Charlottesville, Virginia

Correspondence: Address reprint requests to Lukas K. Tamm, Tel.: 434-982-3578; Fax: 434-982-1616; E-mail: lkt2e{at}virginia.edu.

Sterols play a crucial regulatory and structural role in the lateral organization of eukaryotic cell membranes. Cholesterol has been connected to the possible formation of ordered lipid domains (rafts) in mammalian cell membranes. Lipid rafts are composed of lipids in the liquid-ordered (l_o) phase and are surrounded with lipids in the liquid-disordered (l_d) phase. Cholesterol and sphingomyelin are thought to be the principal components of lipid rafts in cell and model membranes. We have used fluorescence microscopy and fluorescence recovery after photobleaching in planar supported lipid bilayers composed of porcine brain phosphatidylcholine (bPC), porcine brain sphingomyelin (bSM), and cholesterol to map the composition-dependence of l_d/l_o phase coexistence. Cholesterol decreases the fluidity of bPC bilayers, but disrupts the highly ordered gel phase of bSM, leading to a more fluid membrane. When mixed with bPC/bSM (1:1) or bPC/bSM (2:1), cholesterol induces the formation of l_o phase domains. The fraction of the membrane in the l_o phase was found to be directly proportional to the cholesterol concentration in both phospholipid mixtures, which implies that a significant fraction of bPC cosegregates into l_o phase domains. Images reveal a percolation threshold, i.e., the point where rafts become connected and fluid domains disconnected, when 45–50% of the total membrane is converted to the l_o phase. This happens between 20 and 25 mol % cholesterol in 1:1 bPC/bSM bilayers and between 25 and 30 mol % cholesterol in 2:1 bPC/bSM bilayers at room temperature, and at 35 mol % cholesterol in 1:1 bPC/bSM bilayers at 37°C. Area fractions of l_o phase lipids obtained in multilamellar liposomes by a fluorescence resonance energy transfer method confirm and support the results obtained in planar lipid bilayers.

This article has been cited by other articles:

				T. C. Anglin and J. C. Conboy Lateral Pressure Dependence of the Phospholipid Transmembrane Diffusion Rate in Planar-Supported Lipid Bilayers Biophys. J., July 1, 2008; 95(1): 186 - 193. [Abstract] [Full Text] [PDF]

				B. M. Stott, M. P. Vu, C. O. McLemore, M. S. Lund, E. Gibbons, T. J. Brueseke, H. A. Wilson-Ashworth, and J. D. Bell Use of fluorescence to determine the effects of cholesterol on lipid behavior in sphingomyelin liposomes and erythrocyte membranes J. Lipid Res., June 1, 2008; 49(6): 1202 - 1215. [Abstract] [Full Text] [PDF]

				A. G. Ayuyan and F. S. Cohen Raft Composition at Physiological Temperature and pH in the Absence of Detergents Biophys. J., April 1, 2008; 94(7): 2654 - 2666. [Abstract] [Full Text] [PDF]

				K. Muller, P. Muller, G. Pincemy, A. Kurz, and C. Labbe Characterization of Sperm Plasma Membrane Properties after Cholesterol Modification: Consequences for Cryopreservation of Rainbow Trout Spermatozoa Biol Reprod, March 1, 2008; 78(3): 390 - 399. [Abstract] [Full Text] [PDF]

				M. D. Collins and S. L. Keller Tuning lipid mixtures to induce or suppress domain formation across leaflets of unsupported asymmetric bilayers PNAS, January 8, 2008; 105(1): 124 - 128. [Abstract] [Full Text] [PDF]

				A. Margineanu, J.-i. Hotta, M. Van der Auweraer, M. Ameloot, A. Stefan, D. Beljonne, Y. Engelborghs, A. Herrmann, K. Mullen, F. C. De Schryver, et al. Visualization of Membrane Rafts Using a Perylene Monoimide Derivative and Fluorescence Lifetime Imaging Biophys. J., October 15, 2007; 93(8): 2877 - 2891. [Abstract] [Full Text] [PDF]

				L. Wessels, M. W. Elting, D. Scimeca, and K. Weninger Rapid Membrane Fusion of Individual Virus Particles with Supported Lipid Bilayers Biophys. J., July 15, 2007; 93(2): 526 - 538. [Abstract] [Full Text] [PDF]

				O. Coban, J. Popov, M. Burger, D. Vobornik, and L. J. Johnston Transition from Nanodomains to Microdomains Induced by Exposure of Lipid Monolayers to Air Biophys. J., April 15, 2007; 92(8): 2842 - 2853. [Abstract] [Full Text] [PDF]

				S. Garg, J. Ruhe, K. Ludtke, R. Jordan, and C. A. Naumann Domain Registration in Raft-Mimicking Lipid Mixtures Studied Using Polymer-Tethered Lipid Bilayers Biophys. J., February 15, 2007; 92(4): 1263 - 1270. [Abstract] [Full Text] [PDF]

				A. M. Davey, R. P. Walvick, Y. Liu, A. A. Heikal, and E. D. Sheets Membrane Order and Molecular Dynamics Associated with IgE Receptor Cross-Linking in Mast Cells Biophys. J., January 1, 2007; 92(1): 343 - 355. [Abstract] [Full Text] [PDF]

				V. Kiessling, J. M. Crane, and L. K. Tamm Transbilayer Effects of Raft-Like Lipid Domains in Asymmetric Planar Bilayers Measured by Single Molecule Tracking Biophys. J., November 1, 2006; 91(9): 3313 - 3326. [Abstract] [Full Text] [PDF]

				B. G. Tenchov, R. C. MacDonald, and D. P. Siegel Cubic Phases in Phosphatidylcholine-Cholesterol Mixtures: Cholesterol as Membrane "Fusogen" Biophys. J., October 1, 2006; 91(7): 2508 - 2516. [Abstract] [Full Text] [PDF]

				A. G. Ayuyan and F. S. Cohen Lipid Peroxides Promote Large Rafts: Effects of Excitation of Probes in Fluorescence Microscopy and Electrochemical Reactions during Vesicle Formation Biophys. J., September 15, 2006; 91(6): 2172 - 2183. [Abstract] [Full Text] [PDF]

				C. Y. Gomez and T. J. Hope Mobility of Human Immunodeficiency Virus Type 1 Pr55Gag in Living Cells. J. Virol., September 1, 2006; 80(17): 8796 - 8806. [Abstract] [Full Text] [PDF]

				M. J. Swamy, L. Ciani, M. Ge, A. K. Smith, D. Holowka, B. Baird, and J. H. Freed Coexisting Domains in the Plasma Membranes of Live Cells Characterized by Spin-Label ESR Spectroscopy Biophys. J., June 15, 2006; 90(12): 4452 - 4465. [Abstract] [Full Text] [PDF]

				J. E. Shaw, R. F. Epand, R. M. Epand, Z. Li, R. Bittman, and C. M. Yip Correlated Fluorescence-Atomic Force Microscopy of Membrane Domains: Structure of Fluorescence Probes Determines Lipid Localization Biophys. J., March 15, 2006; 90(6): 2170 - 2178. [Abstract] [Full Text] [PDF]

				J. Liu and J. C. Conboy 1,2-Diacyl-Phosphatidylcholine Flip-Flop Measured Directly by Sum-Frequency Vibrational Spectroscopy Biophys. J., October 1, 2005; 89(4): 2522 - 2532. [Abstract] [Full Text] [PDF]

				Z. Salamon, S. Devanathan, I. D. Alves, and G. Tollin Plasmon-waveguide Resonance Studies of Lateral Segregation of Lipids and Proteins into Microdomains (Rafts) in Solid-supported Bilayers J. Biol. Chem., March 25, 2005; 280(12): 11175 - 11184. [Abstract] [Full Text] [PDF]

				V. Pata and N. Dan Effect of Membrane Characteristics on Phase Separation and Domain Formation in Cholesterol-Lipid Mixtures Biophys. J., February 1, 2005; 88(2): 916 - 924. [Abstract] [Full Text] [PDF]

				P. I. Kuzmin, S. A. Akimov, Y. A. Chizmadzhev, J. Zimmerberg, and F. S. Cohen Line Tension and Interaction Energies of Membrane Rafts Calculated from Lipid Splay and Tilt Biophys. J., February 1, 2005; 88(2): 1120 - 1133. [Abstract] [Full Text] [PDF]

				B. L. Stottrup, D. S. Stevens, and S. L. Keller Miscibility of Ternary Mixtures of Phospholipids and Cholesterol in Monolayers, and Application to Bilayer Systems Biophys. J., January 1, 2005; 88(1): 269 - 276. [Abstract] [Full Text] [PDF]

				S. Schuck and K. Simons Polarized sorting in epithelial cells: raft clustering and the biogenesis of the apical membrane J. Cell Sci., December 1, 2004; 117(25): 5955 - 5964. [Abstract] [Full Text] [PDF]