title: Cell surface organization of stress-inducible proteins ULBP and MICA that stimulate human NK cells and T cells via NKG2D.
abstract: Cell surface proteins major histocompatibility complex (MHC) class I-related chain A (MICA) and UL16-binding proteins (ULBP) 1, 2, and 3 are up-regulated upon infection or tumor transformation and can activate human natural killer (NK) cells. Patches of cross-linked raft resident ganglioside GM1 colocalized with ULBP1, 2, 3, or MICA, but not CD45. Thus, ULBPs and MICA are expressed in lipid rafts at the cell surface. Western blotting revealed that glycosylphosphatidylinositol (GPI)-anchored ULBP3 but not transmembrane MICA, MHC class I protein, or transferrin receptor, accumulated in detergent-resistant membranes containing GM1. Thus, MICA may have a weaker association with lipid rafts than ULBP3, yet both proteins accumulate at an activating human NK cell immune synapse. Target cell lipid rafts marked by green fluorescent protein-tagged GPI also accumulate with ULBP3 at some synapses. Electron microscopy reveals constitutive clusters of ULBP at the cell surface. Regarding a specific molecular basis for the organization of these proteins, ULBP1, 2, and 3 and MICA are lipid modified. ULBP1, 2, and 3 are GPI anchored, and we demonstrate here that MICA is S-acylated. Finally, expression of a truncated form of MICA that lacks the putative site for S-acylation and the cytoplasmic tail can be expressed at the cell surface, but is unable to activate NK cells.
authors.affiliation: Department of Biological Sciences, Imperial College, London SW7 2AZ, UK.
authors.forename: Konstantina
authors.initials: K
authors.lastname: Eleme
authors.forename: Sabrina B
authors.initials: SB
authors.lastname: Taner
authors.forename: Björn
authors.initials: B
authors.lastname: Onfelt
authors.forename: Lucy M
authors.initials: LM
authors.lastname: Collinson
authors.forename: Fiona E
authors.initials: FE
authors.lastname: McCann
authors.forename: N Jan
authors.initials: NJ
authors.lastname: Chalupny
authors.forename: David
authors.initials: D
authors.lastname: Cosman
authors.forename: Colin
authors.initials: C
authors.lastname: Hopkins
authors.forename: Anthony I
authors.initials: AI
authors.lastname: Magee
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Davis
mesh_terms: D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D058851:GPI-Linked Proteins; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D007694:Killer Cells, Natural / Q000276:immunology* / Q000378:metabolism* / Q000648:ultrastructure; D021962:Membrane Microdomains / Q000276:immunology / Q000378:metabolism; D008565:Membrane Proteins; D008854:Microscopy, Electron; D055655:NK Cell Lectin-Like Receptor Subfamily K; D011971:Receptors, Immunologic / Q000378:metabolism*; D055607:Receptors, Natural Killer Cell; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D002352:Carrier Proteins; D017931:DNA Primers; D058851:GPI-Linked Proteins; D015395:Histocompatibility Antigens Class I; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; C527085:KLRK1 protein, human; C099187:MHC class I-related chain A; D008565:Membrane Proteins; D055655:NK Cell Lectin-Like Receptor Subfamily K; D011971:Receptors, Immunologic; D055607:Receptors, Natural Killer Cell; C423231:ULBP1 protein, human; C423230:ULBP2 protein, human; C423229:ULBP3 protein, human