Cholesterol Depletion Induces Solid-like Regions in the Plasma Membrane

Department of Chemistry, Molecular and Cellular Physiology, and Biophysics Program, Stanford University, Stanford, California 94305-5080, USA.
Biophysical Journal (Impact Factor: 3.97). 02/2006; 90(3):927-38. DOI: 10.1529/biophysj.105.070524
Source: PubMed


Glycosylphosphatidylinositol-linked and transmembrane major histocompatibility complex (MHC) class II I-E(k) proteins, as well as N-(6-tetramethylrhodaminethiocarbamoyl)-1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine (Tritc-DHPE), are used as probes to determine the effect of cholesterol concentration on the organization of the plasma membrane at temperatures in the range 22 degrees C-42 degrees C. Cholesterol depletion caused a decrease in the diffusion coefficients for the MHC II proteins and also for a slow fraction of the Tritc-DHPE population. At 37 degrees C, reduction of the total cell cholesterol concentration results in a smaller suppression of the translational diffusion for I-E(k) proteins (twofold) than was observed in earlier work at 22 degrees C (five sevenfold) Vrljic, M., S. Y. Nishimura, W. E. Moerner, and H. M. McConnell. 2005. Biophys. J. 88:334-347. At 37 degrees C, the diffusion of both I-E(k) proteins is Brownian (0.9 < alpha-parameter < 1.1). More than 99% of the protein population diffuses homogeneously when imaged at 65 frames per s. As the temperature is raised from 22 degrees C to 42 degrees C, a change in activation energy is seen at approximately 35 degrees C in the Arrhenius plots. Cytoskeletal effects appear to be minimal. These results are consistent with a previously described model of solid-like domain formation in the plasma membrane.

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    • "Several groups (6–9) have measured MHC class II mobility by single molecule tracking, which resolves dynamics at intervals in the tens of milliseconds. Based on measurements for the diffusion of MHC class II expressed on CHO cells, as GPI-anchored or transmembrane molecules, most MHC molecules appear to be highly mobile and diffusing at rates similar to GPI-anchored proteins. "
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    ABSTRACT: Major histocompatibility complex (MHC) class II molecules are ligands for CD4(+) T cells and are critical for initiating the adaptive immune response. This review is focused on what is currently known about MHC class II organization at the plasma membrane of antigen presenting cells and how this affects antigen presentation to T cells. The organization and diffusion of class II molecules have been measured by a variety of biochemical and microscopic techniques. Membrane lipids and other proteins have been implicated in MHC class II organization and function. However, when compared with the organization of MHC class I or TCR complexes, much less is known about MHC class II. Since clustering of T cell receptors occurs during activation, the organization of MHC molecules prior to recognition and during synapse formation may be critical for antigen presentation.
    Frontiers in Immunology 04/2014; 5:158. DOI:10.3389/fimmu.2014.00158
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    • "They are thought to play an important role in various cellular processes such as trafficking and signaling to cite but a few [7,8]. In addition, perturbations (like disruption by cholesterol removal) have important effects on cell responses compared to control [9,10]. Surprisingly some recent works even suggest that the non-raftparts of the membrane are protein free [11]. "
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    ABSTRACT: Background In the classical view, cell membrane proteins undergo isotropic random motion, that is a 2D Brownian diffusion that should result in an homogeneous distribution of concentration. It is, however, far from the reality: Membrane proteins can assemble into so-called microdomains (sometimes called lipid rafts) which also display a specific lipid composition. We propose a simple mechanism that is able to explain the colocalization of protein and lipid rafts. Results Using very simple mathematical models and particle simulations, we show that a variation of membrane viscosity directly leads to variation of the local concentration of diffusive particles. Since specific lipid phases in the membrane can account for diffusion variation, we show that, in such a situation, the freely diffusing proteins (or any other component) still undergo a Brownian motion but concentrate in areas of lower diffusion. The amount of this so-called overconcentration at equilibrium issimply related to the ratio of diffusion coefficients between zones of high and low diffusion. Expanding the model to include particle interaction, we show that inhomogeneous diffusion can impact particles clusterization as well. The clusters of particles were more numerous and appear for a lower value of interaction strength in the zones of low diffusion compared to zones of high diffusion. Conclusion Provided we assume stable viscosity heterogeneity in the membrane, our model propose a simple mechanism to explain particle concentration heterogeneity. It has also a non-trivial impact on density of particles when interaction is added. This could potentially have an impact on membrane chemical reactions and oligomerization.
    BMC Biophysics 04/2012; 5(1):6. DOI:10.1186/2046-1682-5-6 · 2.89 Impact Factor
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    • "3T3-A14 YFP-C-terminus of HRas MβCD SPT No change Nishimura et al. [43] "
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    ABSTRACT: Studies of the diffusion of proteins and lipids in the plasma membrane of cells have long pointed to the presence of membrane domains. A major challenge in the field of membrane biology has been to characterize the various cellular structures and mechanisms that impede free diffusion in cell membranes and determine the consequences that membrane compartmentalization has on cellular biology. In this review, we will provide a brief summary of the classes of domains that have been characterized to date, focusing on recent efforts to identify the properties of lipid rafts in cells through measurements of protein and lipid diffusion.
    Biochimica et Biophysica Acta 01/2009; 1788(1-1788):245-253. DOI:10.1016/j.bbamem.2008.10.024 · 4.66 Impact Factor
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