K33-linked polyubiquitination of T cell receptor-zeta regulates proteolysis-independent T cell signaling

Immunity. 2010 Jul 23;33(1):60-70. doi: 10.1016/j.immuni.2010.07.002.

Abstract

Tagging the cell surface receptor with ubiquitin is believed to provide a signal for the endocytic pathway. E3 ubiquitin ligases such as Cbl-b and Itch have been implicated in T cell activation and tolerance induction. However, the underlying mechanisms remain unclear. We describe that in mice deficient in the E3 ubiquitin ligases Cbl-b and Itch, T cell activation was augmented, accompanied by spontaneous autoimmunity. The double-mutant T cells exhibited increased phosphorylation of the T cell receptor-zeta (TCR-zeta) chain, whereas the endocytosis and stability of the TCR complex were not affected. TCR-zeta was polyubiquitinated via a K33-linkage, which affected its phosphorylation and association with the zeta chain-associated protein kinase Zap-70. The juxtamembrane K54 residue in TCR-zeta was identified to be a primary ubiquitin conjugation site, whose mutation increased its phosphorylation and association of TCR-zeta and Zap-70. Thus, the present study reveals unconventional K33-linked polyubiquitination in nonproteolytic regulation of cell-surface-receptor-mediated signal transduction.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics*
  • Animals
  • Autoimmunity / genetics
  • Endocytosis / immunology
  • Humans
  • Jurkat Cells
  • Lymphocyte Activation / genetics
  • Lysine / genetics
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mutagenesis, Site-Directed
  • Mutation / genetics
  • Protein Binding
  • Proto-Oncogene Proteins c-cbl / genetics*
  • Receptors, Antigen, T-Cell / genetics
  • Receptors, Antigen, T-Cell / metabolism*
  • Signal Transduction / immunology
  • T-Lymphocytes / immunology
  • T-Lymphocytes / metabolism*
  • T-Lymphocytes / pathology
  • Ubiquitin-Protein Ligases / genetics*
  • Ubiquitination / genetics
  • ZAP-70 Protein-Tyrosine Kinase / metabolism

Substances

  • Adaptor Proteins, Signal Transducing
  • Cblb protein, mouse
  • Receptors, Antigen, T-Cell
  • antigen T cell receptor, zeta chain
  • Itch protein, mouse
  • Proto-Oncogene Proteins c-cbl
  • Ubiquitin-Protein Ligases
  • ZAP-70 Protein-Tyrosine Kinase
  • Lysine