Determination of cellular lipids bound to human CD1d molecules (original) (raw)
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Proceedings of the National Academy of Sciences of the United States of America, 2011
Unlike the dominant role of one class II invariant chain peptide (CLIP) in blocking MHC class II, comparative lipidomics analysis shows that human cluster of differentiation (CD) proteins CD1a, CD1b, CD1c, and CD1d bind lipids corresponding to hundreds of diverse accurate mass retention time values. Although most ions were observed in association with several CD1 proteins, ligands binding selectively to one CD1 isoform allowed the study of how differing antigen-binding grooves influence lipid capture. Although the CD1b groove is distinguished by its unusually large volume (2,200 Å(3)) and the T' tunnel, the average mass of compounds eluted from CD1b was similar to that of lipids from CD1 proteins with smaller grooves. Elution of small ligands from the large CD1b groove might be explained if two small lipids bind simultaneously in the groove. Crystal structures indicate that all CD1 proteins can capture one antigen with its hydrophilic head group exposed for T-cell recognition, ...
CD1a selectively captures endogenous cellular lipids that broadly block T cell response
Journal of Experimental Medicine
We optimized lipidomics methods to broadly detect endogenous lipids bound to cellular CD1a proteins. Whereas membrane phospholipids dominate in cells, CD1a preferentially captured sphingolipids, especially a C42, doubly unsaturated sphingomyelin (42:2 SM). The natural 42:2 SM but not the more common 34:1 SM blocked CD1a tetramer binding to T cells in all human subjects tested. Thus, cellular CD1a selectively captures a particular endogenous lipid that broadly blocks its binding to TCRs. Crystal structures show that the short cellular SMs stabilized a triad of surface residues to remain flush with CD1a, but the longer lipids forced the phosphocholine group to ride above the display platform to hinder TCR approach. Whereas nearly all models emphasize antigen-mediated T cell activation, we propose that the CD1a system has intrinsic autoreactivity and is negatively regulated by natural endogenous inhibitors selectively bound in its cleft. Further, the detailed chemical structures of nat...
Journal of Immunological Methods, 2009
Antigen presenting molecules play an important role in both innate and adoptive immune responses by priming and activating T cells. Among them, CD1 molecules have been identified to present both exogenous and endogenous lipid antigens to CD1-restricted T cells. The involvement of CD1-restricted T cells in autoimmune diseases and in defense against infectious diseases, however, remains largely unknown. Identifying novel antigenic lipids that bind to CD1 molecules and understanding the role of CD1-restricted T cells should lead to the successful development of vaccines, because the lipids can be used as antigens and also as adjuvants. In this paper, we have constructed functional recombinant human CD1 dimeric proteins and established a competitive ELISA assay to measure the lipid binding to CD1 molecules using the CD1 dimers. By using the competitive ELISA assay, we were able to show that the lipid extracts from murine malaria parasites can actually be loaded onto CD1 molecules. In addition, we have demonstrated that artificial antigen-presenting cells, which consist of magnetic beads coated with CD1d dimer and anti-CD28 antibody, stimulated and expanded human invariant NKT cells as efficiently as autologous immature DCs. A set of the tools presented in the current study should be valuable for screening various CD1 molecule-binding lipid antigens and for isolating CD1-restricted T cells.
Structural determination of lipid antigens captured at the CD1d-T-cell receptor interface
Proceedings of the National Academy of Sciences of the United States of America, 2017
Glycolipid antigens recognized by αβ T-cell receptors (TCRs) drive the activation of invariant natural killer T (iNKT) cells, a specialized subset of innate T lymphocytes. Glycolipids with α-linked anomeric carbohydrates have been identified as potent microbial lipid antigens for iNKT cells, and their unusual α-anomeric linkage has been thought to define a "foreign" lipid antigen motif. However, mammals use endogenous lipids to select iNKT cells, and there is compelling evidence for iNKT cell responses in various types of sterile inflammation. The nature of endogenous or environmental lipid antigens encountered by iNKT cells is not well defined. Here, we sought to identify lipid antigens in cow's milk, a prominent part of the human diet. We developed a method to directly capture lipid antigens within CD1d-lipid-TCR complexes, while excluding CD1d bound to nonantigenic lipids, followed by direct biochemical analysis of the lipid antigens trapped at the TCR-CD1d interfac...
Functional CD1a is stabilized by exogenous lipids
European Journal of Immunology, 2006
Self-glycosphingolipids bind to surface CD1 molecules and are readily displaced by other CD1 ligands. This capacity to exchange antigens at the cell surface is not common to other antigen-presenting molecules and its physiological importance is unclear. Here we show that a large pool of cell-surface CD1a, but not CD1b molecules, is stabilized by exogenous lipids present in serum. Under serum deprivation CD1a molecules are altered and functionally inactive, as they are unable to present lipid antigens to T cells. Glycosphingolipids and phospholipids bind to, and restore functionality to CD1a without the contribution of newly synthesized and recycling CD1a molecules. The dependence of CD1a stability on exogenous lipids is not related to its intracellular traffic and rather to its antigen-binding pockets. These results indicate a functional dichotomy between CD1a and CD1b molecules and provide new information on how the lipid antigenic repertoire is immunologically sampled.
Murine CD1d-Restricted T Cell Recognition of Cellular Lipids
Immunity, 2000
a synthetic acylphytosphingolipid originally isolated from a marine sponge (Kawano et al.negative, or DN) (Bendelac et al., 1994, 1995). At least * Division of Rheumatology, Immunology, and Allergy two distinct populations of CD1d-restricted ␣ T cells Brigham and Women's Hospital have been identified in the mouse, based on their T and Harvard Medical School cell receptor (TCR) structures. One population has a Boston, Massachusetts 02115 characteristic invariant TCR␣ chain (V␣14/J␣281) paired † Immunology Section preferentially with TCR chains utilizing V8. These cells Department of Cell and Molecular Biology comprise a part of the NKT cell subset, T cells that Lund University express receptors of the NK complex (Lantz and Bende-Solvegatan 21 lac, 1994; Taniguchi et al., 1996). More recently, T cells S-223 62 Lund expressing diverse TCR␣ and - chains have also been Sweden found that recognize mCD1d molecules (Cardell et al., ‡ Pharmaceutical Research Laboratory 1995; Behar et al., 1999; Chiu et al., 1999). Similar to Kirin Brewery those of the "NKT" subset, CD1d-restricted cells be-Gunma 370-12 longing to this "diverse TCR" population can secrete Japan significant amounts of IL-4 and IL-10 in addition to IFN␥ and may thus contribute to determining the TH 1 /TH 2 cytokine balance in immune responses (Yoshimoto et Summary al., 1995; Behar et al., 1999). CD1d-restricted T cells have also been associated with various immunologically NKT cells are associated with immunological control mediated functions, such as preventing development of of autoimmune disease and cancer and can recognize autoimmune diabetes, tumor rejection, and modulating cell surface mCD1d without addition of exogenous IgG responses during protozoal infections (Cui et al., antigens. Cellular antigens presented by mCD1d have 1997; Wilson et al., 1998; Schofield et al., 1999). not been identified, although NKT cells can recognize The origin and the identity of the natural antigens a synthetic glycolipid, ␣-GalCer. Here we show that recognized by CD1d-restricted T cells remain unknown. after addition of a lipid extract from a tumor cell line, It has been postulated that mCD1d-restricted NKT cells plate-bound mCD1d molecules stimulated an NKT cell may recognize a single or a conserved set of antigens, hybridoma. This hybridoma also responded strongly since their cannonical ␣ chains and limited  chain diverto three purified phospholipids, but failed to recognize sity result in TCRs of comparatively little structural vari-␣-GalCer. Seven of sixteen other mCD1d restricted ability, whereas the diverse TCR population of mCD1dhybridomas also showed a response to certain purified restricted T cells may have heterogeneous antigenic phospholipids. These findings suggest NKT cells can specificities (Cardell et al., 1995; Behar et al., 1999; Chiu recognize cellular antigens distinct from ␣-GalCer and et al., 1999). Both T cell populations can recognize CD1d identify phospholipids as potential self-antigens premolecules on antigen-presenting cells (APCs) in vitro, sented by mCD1d. without requiring addition of exogenous antigens (Bendelac et al.A novel recognition motif of human NKT antigen receptor for a to S. M. B. and AI28973 to M. B. B. glycolipid ligand. Int. Immunol. 11, 881-887.
Molecular Mechanism of Lipopeptide Presentation by CD1a
Immunity, 2005
proteins can be separated into two groups based on 1 Department of Molecular Biology their sequence similarity and immunological functions. 2 Skaggs Institute for Chemical Biology In humans, group 1 CD1 consists of CD1a, CD1b, The Scripps Research Institute CD1c, and CD1e, whereas the only group 2 isoform is 10550 North Torrey Pines Road CD1d (Calabi et al., 1989). Whereas group 1 CD1 pro-La Jolla, California 92037 teins are thought to participate in host defense by pre-3 Division of Rheumatology, Immunology and Allergy senting microbial lipid antigens to cytotoxic T cells, Brigham and Women's Hospital group 2 proteins respond to endogenous antigens and Harvard Medical School carry out immunoregulatory functions (Gumperz and 1 Jimmy Fund Way Brenner, 2001). Nevertheless, recent studies have Boston, Massachusetts 02115 established a role for group 2 CD1 in host defense (Fi-; Skold and Behar, 2003; Vincent et University of Notre Dame al., 2003). 251 Nieuwland Science Hall CD1a differs from the other group 1 CD1 molecules Notre Dame, Indiana 46556 in terms of cellular expression and intracellular localiza-5 Mass Spectrometry Resource tion. Firstly, CD1a is the only CD1 protein to be consti-Boston University School of Medicine tutively expressed at high levels on LCs, where Lang-Boston, Massachusetts 02118 erin, an LC-expressed C type lectin participates in 6 Department of Biochemistry glycolipid antigen capture and presentation to T cells Oxford Glycobiology Institute (Hunger et al., 2004). Secondly, unlike other CD1 iso-University of Oxford forms, which have endosomal targeting sequences in Oxford OX1 3QU their cytoplasmic tails and recycle to LAMP1 + late en-United Kingdom dosomes, the short cytoplasmic tail of CD1a lacks such motifs, so that this isoform localizes predominantly at the cell surface with only low levels in recycling endo-Summary somes. CD1 exhibits a similar fold and architecture as major CD1a is expressed on Langerhans cells (LCs) and histocompatibility complex (MHC) class I molecules, dendritic cells (DCs), where it mediates T cell recognibut its binding groove has evolved into a narrow and tion of glycolipid and lipopeptide antigens that condeep hydrophobic cleft, more suited to binding lipids tain either one or two alkyl chains. We demonstrate and glycolipids (Gadola et al., 2002; Zajonc et al., 2003; here that CD1a-restricted T cells can discriminate the Zeng et al.
Recent advances in processing and presentation of CD1 bound lipid antigens
Current Opinion in Immunology, 2010
It is well established that different populations of ab T lymphocytes can recognize not only peptides in the context of MHC class I and class II molecules, but also foreign and selflipids in association with CD1 proteins, which share structural similarities with MHC class I molecules. CD1 molecules are comprised of five isoforms, known as group 1 (CD1a, b, c, e) and group 2 (CD1d) CD1, presenting lipid antigens to conventional T lymphocytes or innate-like T cells bearing an invariant T cell receptor (TCR) and known as invariant NKT (iNKT) cells. During the last couple of years, several papers have been published describing important aspects of the mechanisms controlling the processing and presentation of endogenous and exogenous CD1 lipid antigens, which will be the main focus of this review.