title: T-cell antigen receptor peptides inhibit signal transduction within the membrane bilayer.
abstract: Previous studies have shown that a synthetic peptide (core peptide, CP) corresponding to a 9-amino-acid region in the transmembrane domain of the alpha subunit of the T-cell antigen receptor (TCR) can suppress T-cell function in vitro and in vivo. The aim of these experiments was to determine the cellular site and molecular mechanism of CP inhibition in T cells. The cytochrome c-sensitive TCR-expressing hybridoma (2B4) was stimulated with pigeon cytochrome c antigen, anti-CD3 crosslinking, or PMA and ionomycin, in the presence or absence of CP, and the resulting IL-2 produced was measured in a bioassay using an IL-2-dependent cell line (CTLL-2). In the presence of CP, IL-2 production was inhibited following antigen-induced stimulation. By contrast, when stimulated with cross-linking antibodies to the CD3 complex or with PMA and ionomycin, both of which activate T cells downstream of the TCR antigen recognition site, CP had no effect on IL-2 production. These experiments suggest that CP interferes with TCR function by inhibiting T-cell activation at the transmembrane/receptor level. In addition, we show that CP inhibits early TCR signal transduction events such as TCR zeta chain phosphorylation following stimulation with either antigen or anti-CD3-crosslinking antibodies, although this is unlikely to be the mechanism leading to the reduced IL-2 production.
authors.affiliation: Department of Rheumatology, Westmead Hospital, Sydney, New South Wales, Australia.
authors.forename: Xin M
authors.initials: XM
authors.lastname: Wang
authors.forename: Julianne T
authors.initials: JT
authors.lastname: Djordjevic
authors.forename: Nozomu
authors.initials: N
authors.lastname: Kurosaka
authors.forename: Stephen
authors.initials: S
authors.lastname: Schibeci
authors.forename: Lianne
authors.initials: L
authors.lastname: Lee
authors.forename: Peter
authors.initials: P
authors.lastname: Williamson
authors.forename: Nicholas
authors.initials: N
authors.lastname: Manolios
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000938:Antigen-Presenting Cells / Q000187:drug effects / Q000276:immunology; D017252:CD3 Complex / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology*; D003432:Cross-Linking Reagents; D003574:Cytochrome c Group / Q000276:immunology; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000096:biosynthesis; D015759:Ionomycin / Q000494:pharmacology; D008051:Lipid Bilayers / Q000276:immunology; D008213:Lymphocyte Activation; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D017252:CD3 Complex; D003432:Cross-Linking Reagents; D003574:Cytochrome c Group; D007376:Interleukin-2; D008051:Lipid Bilayers; D008565:Membrane Proteins; D011948:Receptors, Antigen, T-Cell; C054979:antigen T cell receptor, zeta chain; C464994:core protein, human; D015759:Ionomycin; D013755:Tetradecanoylphorbol Acetate