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Activation-dependent ubiquitination of a T cell antigen receptor subunit on multiple intracellular lysines

D Hou1, C Cenciarelli, J P Jensen

  • 1Laboratory of Immune Cell Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892.

The Journal of Biological Chemistry
|May 13, 1994
PubMed

Insights

T cell antigen receptor (TCR) zeta chain ubiquitination occurs at multiple lysine sites in its cytoplasmic domain. Specific lysine residues are not critical, as introduced lysines are also ubiquitinated, indicating low specificity.

Area of Science:

  • Immunology
  • Molecular Biology
  • Cell Signaling

Background:

  • T cell antigen receptor (TCR) components, including the zeta chain, undergo ubiquitination upon receptor engagement.
  • Ubiquitination is a key post-translational modification regulating protein function and stability.
  • Understanding the specific sites and regulation of TCR zeta chain ubiquitination is crucial for T cell activation studies.

Purpose of the Study:

  • To identify the specific lysine residues on the TCR zeta chain that serve as ubiquitination sites.
  • To investigate the role of these specific sites in the ubiquitination process and its impact on other TCR subunits.
  • To determine the specificity of the ubiquitination machinery for lysine residues on the zeta chain.

Main Methods:

  • Systematic mutagenesis of the TCR zeta subunit to alter potential ubiquitination sites (lysines).
  • Analysis of ubiquitination patterns on wild-type and mutant zeta chains using biochemical assays.
  • Assessment of the impact of zeta chain mutations on receptor tyrosine phosphorylation and ubiquitination of other TCR components.

Main Results:

  • Ubiquitination of the TCR zeta chain occurs in its cytoplasmic domain, involving multiple lysine residues for both mono- and polyubiquitination.
  • Mutation of all identified potential ubiquitination sites on the zeta chain did not prevent receptor tyrosine phosphorylation or the ubiquitination of other TCR subunits.
  • Exogenously introduced lysines at non-native positions within the zeta molecule were also successfully ubiquitinated.

Conclusions:

  • The ubiquitination of the T cell antigen receptor zeta chain is not restricted to specific lysine residues.
  • Once targeted for ubiquitination, the TCR machinery exhibits broad specificity for available lysine sites on the zeta chain.
  • These findings suggest a non-specific mechanism for TCR zeta chain ubiquitination, potentially impacting T cell signaling regulation.

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