Gupta N, Wollscheid B, Watts JD, Scheer B, Aebersold R, DeFranco AL.. Quantitative proteomic analysis of B cell lipid rafts reveals that ezrin regulates antigen receptor-mediated lipid raft dynamics. Nat Immunol 7: 625-633

Department of Microbiology and Immunology, University of California, San Francisco, California 94143, USA.
Nature Immunology (Impact Factor: 24.97). 07/2006; 7(6):625-33. DOI: 10.1038/ni1337
Source: PubMed

ABSTRACT Ligation of the B cell antigen receptor (BCR) with antigen induces lipid raft coalescence, a process that occurs after crosslinking of a variety of signaling receptors and is thought to potentiate cellular activation. To investigate lipid raft dynamics during BCR signaling, we quantitatively analyzed the B cell lipid raft proteome. BCR engagement induced dissociation of the adaptor protein ezrin from lipid rafts as well as threonine dephosphorylation of ezrin and its concomitant detachment from actin, indicating a transient uncoupling of lipid rafts from the actin cytoskeleton. Expression of constitutively active ezrin chimeras inhibited the BCR-induced coalescence of lipid rafts. Our data demonstrate that the release of ezrin from lipid rafts acts as a critical trigger that regulates lipid raft dynamics during BCR signaling.

Download full-text


Available from: Bernd Wollscheid, Aug 20, 2015
  • Source
    • "For example, a measure for BCR-Lyn association can be useful in analyzing dynamical FRET between Lyn FL/Lyn16 (lipid raft probe) and BCR cytoplasmic domains [80]. Estimation of the BCR fraction localized in sphingolipid domains before and after antigen ligation , from BCR-lipid raft simulations, can be compared with data obtained from proteomic measurements in [82] (or similar measurements). Another study of lipid rafts in B lymphocytes , based on biochemical measurements, indicated that disruption of rafts (by methyl-beta-cyclodextrin) can actually lead to increased signaling. "
    [Show abstract] [Hide abstract]
    ABSTRACT: B and T lymphocytes activate the humoral and cellular arms of the adaptive immune system. The adaptive strategy works because receptors of adaptive immune cells can mount an immune response based on their affinity for antigens. Thus, affinity discrimination is central to adaptive immunity and has important biomedical ramifications. Due to its intricate connection to the affinity maturation process, affinity discrimination has a special significance in B-cell-mediated immune response. The role of affinity-matured high-affinity antibodies is increasingly recognized in vaccine development. In this paper, we discuss the recent progress made in mathematical and computational studies to explore the cellular and molecular mechanisms of B-cell affinity discrimination. Formation of B-cell receptor (BCR) oligomers and BCR-lipid rafts, upon antigenic stimulation, emerge to be key factors in B-cell affinity discrimination (at the level of single cells). It also provides a new way of thinking about kinetic proofreading and serial triggering, concepts that have been widely utilized to understand affinity discrimination in adaptive immune cells. Potential future applications of mathematical and computational modeling of affinity discrimination are discussed in the context of autoimmune disorders and vaccine design.
    ISRN Biomathematics 04/2013; 2013. DOI:10.1155/2013/845918
  • Source
    • "A previous example of cross-regulation between rafts and ERM proteins at the plasma membrane has been reported in B-cells, in which ezrin can modulate the dynamics of ordered domains and their ability to contribute to B-cell receptor (BCR) signaling (Gupta et al., 2006; Viola and Gupta, 2007). Gupta et al. (2006) proposed that, in resting B-cells, active ezrin maintains small raft domains that contain signaling molecules and are linked to cortical F-actin and dispersed on the cell surface. On BCR activation, ezrin becomes transiently inactivated and uncouples actin from the plasma membrane domains. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The endothelium maintains a barrier between blood and tissue that becomes more permeable during inflammation. Membrane rafts are ordered assemblies of cholesterol, glycolipids and proteins that modulate proinflammatory cell signaling and barrier function. In epithelial cells, the MAL family members MAL, MAL2 and myeloid-associated differentiation marker (MYADM) regulate the function and dynamics of ordered membrane domains. We analyzed the expression of these three proteins in human endothelial cells and found that only MYADM is expressed. MYADM was confined in ordered domains at the plasma membrane, where it partially colocalized with filamentous actin and cell-cell junctions. siRNA-mediated MYADM knockdown increased permeability, ICAM-1 expression and leukocyte adhesion, all of which are features of an inflammatory response. Barrier function decrease in MYADM-silenced cells was dependent on ICAM-1 expression. Membrane domains and the underlying actin cytoskeleton can regulate each other and are connected by ezrin, radixin and moesin (ERM) proteins. In endothelial cells, MYADM knockdown induced ERM activation. Triple ERM knockdown partially inhibited ICAM-1 increase induced by MYADM siRNA. Importantly, ERM knockdown also reduced ICAM-1 expression in response to the proinflammatory cytokine TNF-α. MYADM therefore regulates the connection between the plasma membrane and the cortical cytoskeleton and so can control the endothelial inflammatory response.
    Molecular biology of the cell 12/2012; 24(4). DOI:10.1091/mbc.E11-11-0914 · 5.98 Impact Factor
  • Source
    • " . This is of particular interest as dephosphorylation of ezrin leads to release of the association between the plasma membrane and the actin cytoskeleton , facilitat - ing the formation of cell conjugates . Interest - ingly , a rapid and global dephosphorylation of ezrin has been observed following stimula - tion of B cells with soluble antigen ( Gupta et al . 2006 ) . In conjunction with Vav , a number of other intracellular B - cell effectors have been implicated in the regulation of cytoskeleton reorganizations following stimulation of the BCR . These include the leukocyte - specific homolog of cortactin HS1 ( Gomez et al . 2006 ; Hao et al . 2004 ; Yamanashi et al . 1997 ) , cofilin"
    [Show abstract] [Hide abstract]
    ABSTRACT: B cells contribute to protective adaptive immune responses through generation of antibodies and long-lived memory cells, following engagement of the B-cell receptor (BCR) with specific antigen. Recent imaging investigations have offered novel insights into the ensuing molecular and cellular events underlying B-cell activation. Following engagement with antigen, BCR microclusters form and act as sites of active signaling through the recruitment of intracellular signaling molecules and adaptors. Signaling through these "microsignalosomes" is propagated and enhanced through B-cell spreading in a CD19-dependent manner. Subsequently, the mature immunological synapse is formed, and functions as a platform for antigen internalization, enabling the antigen presentation to helper T cells required for maximal B-cell activation. In this review, we discuss the emerging and critical role for the cytoskeleton in the coordination and regulation of these molecular events during B-cell activation.
    Cold Spring Harbor perspectives in biology 11/2010; 3(2). DOI:10.1101/cshperspect.a002360 · 8.23 Impact Factor
Show more