Distinct MHC Class II Molecules Are Associated on the Dendritic Cell Surface in Cholesterol-dependent Membrane Microdomains

Experimental Immunology Branch, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 11/2010; 285(46):35303-10. DOI: 10.1074/jbc.M110.147793
Source: PubMed


Very small amounts of MHC class II-peptide complexes expressed on the surface of antigen-presenting cells (APCs) are capable of stimulating antigen-specific CD4 T cells. There is intense interest to elucidate the molecular mechanisms by which these small amounts of MHC-II can cluster, cross-link T cell receptors, and promote T cell proliferation. We now demonstrate that a significant fraction of the total pool of MHC-II molecules on the surface of dendritic cells is physically associated in macromolecular aggregates. These MHC-II/MHC-II interactions have been probed by co-immunoprecipitation analysis of the MHC-II I-A molecule with the related I-E molecule. These molecular associations are maintained in gentle detergents but are disrupted in harsh detergents such as Triton X-100. MHC-II I-A/I-E interactions are disrupted when plasma membrane cholesterol is extracted using methyl β-cyclodextrin, suggesting that lipid raft microdomains are important mediators of these MHC-II interactions. Although it has been proposed that tetraspanin proteins regulate molecular clustering, aggregation, and co-immunoprecipitation in APCs, genetic deletion of the tetraspanin family members CD9 or CD81 had no effect on MHC-II I-A/I-E binding. These data demonstrate that the presence of distinct forms of MHC-II with plasma membrane lipid rafts is required for MHC-II aggregation in APCs and provides a molecular mechanism allowing dendritic cells expressing small amounts of MHC-II-peptide complexes to cross-link and stimulate CD4 T cells.

Download full-text


Available from: Sanjay Khandelwal, Feb 05, 2015
  • Source
    • "A proportion of MHC class II can be found in lipid rafts as measured by detergent extraction followed by sucrose gradient centrifugation (32, 33). The fraction of detergent-insoluble MHC II is reduced upon DC maturation (34). "
    [Show abstract] [Hide abstract]
    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.
    Full-text · Article · Apr 2014 · Frontiers in Immunology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Melanoma cells often display constitutive expression of the major histocompatibility complex (MHC) class II molecules which is associated with a higher metastatic dissemination. The MHC class II molecules during T cell/ professional antigen-presenting cell (APC) interactions are localized, as signalling receptors, into membrane lipid rafts which are thought to be sites of signalling complex assembly. Therefore, with the aim of understanding the molecular mechanisms used by melanoma cells to frustrate an effective anti-tumour response we stimulated a MHC class II constitutive expressing melanoma cell line with a specific antibody that mimics the interaction of T-cell receptor (TCR) with class II molecules. In stimulated melanoma cells we showed through Western blotting and immunofluorescence experiments the recruitment of HLA-DR molecules in lipid raft compartments as well as the c-Jun NH2-terminal kinase activations as a consequence of the class II engagement. Furthermore, we showed that SDS-stable HLA-DR-peptide complexes are recruited in lipid rafts of stimulated melanoma cells. Therefore, in light of the results reported, our hypothesis is that the redistribution of class II molecules into lipid raft microdomains of stimulated melanoma cells as well as the associated activation of signalling pathways, could be useful for melanoma cells to frustrate an effective anti-tumour response.
    No preview · Article · Mar 2011 · International Journal of Oncology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Liver diseases are an increasingly common cause of morbidity and mortality; new approaches for investigation of mechanisms of liver diseases and identification of therapeutic targets are emergent. Lipid rafts (LRs) are specialized domains of cellular membranes that are enriched in saturated lipids; they are small, mobile, and are key components of cellular architecture, protein partition to cellular membranes, and signaling events. LRs have been identified in the membranes of all liver cells, parenchymal and non-parenchymal; more importantly, LRs are active participants in multiple physiological and pathological conditions in individual types of liver cells. This article aims to review experimental-based evidence with regard to LRs in the liver, from the perspective of the liver as a whole organ composed of a multitude of cell types. We have gathered up-to-date information related to the role of LRs in individual types of liver cells, in liver health and diseases, and identified the possibilities of LR-dependent therapeutic targets in liver diseases.
    Full-text · Article · May 2011 · World Journal of Gastroenterology
Show more