title: Constitutive endocytosis and degradation of the pre-T cell receptor.
abstract: The pre-T cell receptor (TCR) signals constitutively in the absence of putative ligands on thymic stroma and signal transduction correlates with translocation of the pre-TCR into glycolipid-enriched microdomains (rafts) in the plasma membrane. Here, we show that the pre-TCR is constitutively routed to lysosomes after reaching the cell surface. The cell-autonomous down-regulation of the pre-TCR requires activation of the src-like kinase p56(lck), actin polymerization, and dynamin. Constitutive signaling and degradation represents a feature of the pre-TCR because the gammadeltaTCR expressed in the same cell line does not exhibit these features. This is also evident by the observation that the protein adaptor/ubiquitin ligase c-Cbl is phosphorylated and selectively translocated into rafts in pre-TCR- but not gammadeltaTCR-expressing cells. A role of c-Cbl-mediated ubiquitination in pre-TCR degradation is supported by the reduction of degradation through pharmacological inhibition of the proteasome and through a dominant-negative c-Cbl ubiquitin ligase as well as by increased pre-TCR surface expression on immature thymocytes in c-Cbl-deficient mice. The pre-TCR internalization contributes significantly to the low surface level of the receptor on developing T cells, and may in fact be a requirement for optimal pre-TCR function.
authors.affiliation: Dipartimento di Biologia e Genetica per le Scienze Mediche, Università degli Studi di Milano, Italy.
authors.forename: Maddalena
authors.initials: M
authors.lastname: Panigada
authors.forename: Simona
authors.initials: S
authors.lastname: Porcellini
authors.forename: Eliane
authors.initials: E
authors.lastname: Barbier
authors.forename: Sonja
authors.initials: S
authors.lastname: Hoeflinger
authors.forename: Pierre-André
authors.initials: PA
authors.lastname: Cazenave
authors.forename: Hua
authors.initials: H
authors.lastname: Gu
authors.forename: Hamid
authors.initials: H
authors.lastname: Band
authors.forename: Harald
authors.initials: H
authors.lastname: von Boehmer
authors.forename: Fabio
authors.initials: F
authors.lastname: Grassi
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001704:Biopolymers / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D034281:Dynamins; D004705:Endocytosis; D020558:GTP Phosphohydrolases / Q000378:metabolism; D006868:Hydrolysis; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D016513:Mice, SCID; D009097:Multienzyme Complexes / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D000199:Actins; D001704:Biopolymers; D009097:Multienzyme Complexes; D011948:Receptors, Antigen, T-Cell; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D020558:GTP Phosphohydrolases; D034281:Dynamins