title: The phosphorylation state of CD3gamma influences T cell responsiveness and controls T cell receptor cycling.
abstract: The T cell receptor (TCR) is internalized following activation of protein kinase C (PKC) via a leucine (Leu)-based motif in CD3gamma. Some studies have indicated that the TCR is recycled back to the cell surface following PKC-mediated internalization. The functional state of recycled TCR and the mechanisms involved in the sorting events following PKC-induced internalization are not known. In this study, we demonstrated that following PKC-induced internalization, the TCR is recycled back to the cell surface in a functional state. TCR recycling was dependent on dephosphorylation of CD3gamma, probably mediated by the serine/threonine protein phosphatase-2A, but independent on microtubules or actin polymerization. Furthermore, in contrast to ligand-mediated TCR sorting, recycling of the TCR was independent of the tyrosine phosphatase CD45 and the Src tyrosine kinases p56(Lck) and p59(Fyn). Studies of mutated TCR and chimeric CD4-CD3gamma molecules demonstrated that CD3gamma did not contain a recycling signal in itself. In contrast, the only sorting information in CD3gamma was the Leu-based motif that mediated lysosomal sorting of chimeric CD4-CD3gamma molecules. Finally, we found a correlation between the phosphorylation state of CD3gamma and T cell responsiveness. Based on these observations a physiological role of CD3gamma and TCR cycling is proposed.
authors.affiliation: Institute of Medical Microbiology and Immunology, University of Copenhagen, The Panum Institute, Building 18.3, Blegdamsvej 3C, DK-2200 Copenhagen, Denmark. vader@biobase.dk
authors.forename: J
authors.initials: J
authors.lastname: Dietrich
authors.forename: T
authors.initials: T
authors.lastname: Bäckström
authors.forename: J P
authors.initials: JP
authors.lastname: Lauritsen
authors.forename: J
authors.initials: J
authors.lastname: Kastrup
authors.forename: M D
authors.initials: MD
authors.lastname: Christensen
authors.forename: F
authors.initials: F
authors.lastname: von Bülow
authors.forename: E
authors.initials: E
authors.lastname: Palmer
authors.forename: C
authors.initials: C
authors.lastname: Geisler
mesh_terms: D000595:Amino Acid Sequence; D015703:Antigens, CD / Q000378:metabolism; D019921:Biotinylation; D015704:CD4 Antigens / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000276:immunology; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells / Q000187:drug effects / Q000276:immunology*; D007700:Kinetics; D007930:Leucine; D017493:Leukocyte Common Antigens / Q000378:metabolism; D008247:Lysosomes / Q000276:immunology; D008969:Molecular Sequence Data; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D054648:Protein Phosphatase 2; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000737:chemistry / Q000502:physiology*; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D016692:Receptors, Antigen, T-Cell, gamma-delta / Q000737:chemistry / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D014162:Transfection
chemical_list: D015703:Antigens, CD; D015704:CD4 Antigens; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D011948:Receptors, Antigen, T-Cell; D016692:Receptors, Antigen, T-Cell, gamma-delta; D011993:Recombinant Fusion Proteins; D015240:Phorbol 12,13-Dibutyrate; D011505:Protein-Tyrosine Kinases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D017493:Leukocyte Common Antigens; D007930:Leucine; D002118:Calcium