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T-cell ubiquitin ligand affects cell death through a functional interaction with apoptosis-inducing factor, a key

Therese S Collingwood1, Evgeniya V Smirnova, Marina Bogush

  • 1Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.

The Journal of Biological Chemistry
|August 22, 2007
PubMed

Insights

The lymphoid protein T-cell ubiquitin ligand (TULA) promotes T-cell apoptosis independently of T-cell receptor signaling. TULA interacts with apoptosis-inducing factor (AIF), enhancing its cell death effects.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Biology

Background:

  • T-cell ubiquitin ligand (TULA), also known as suppressor of T-cell receptor signaling (Sts)-2, is a lymphoid protein involved in protein-tyrosine kinase signaling.
  • TULA interacts with c-Cbl and ubiquitylated proteins, suggesting a role in signal transduction pathways.
  • The precise function of TULA in cellular processes, particularly apoptosis, remains incompletely understood.

Purpose of the Study:

  • To investigate the role of TULA in T-cell apoptosis.
  • To identify TULA-interacting proteins involved in apoptosis.
  • To elucidate the mechanism by which TULA influences apoptosis.

Main Methods:

  • Mass spectrometry-based analysis of TULA protein-protein interactions.
  • RNA interference (RNAi) to assess the necessity of identified interactors.
  • Analysis of subcellular localization and functional analysis of TULA mutants.

Main Results:

  • TULA facilitates T-cell apoptosis independently of T-cell receptor/CD3-mediated signaling and caspase activity.
  • Mass spectrometry identified Apoptosis-Inducing Factor (AIF) as a TULA-binding protein.
  • RNA interference confirmed that AIF is essential for TULA-mediated T-cell apoptosis.
  • Subcellular localization and mutant analyses suggest TULA enhances AIF's apoptotic function by facilitating its interaction with co-factors.

Conclusions:

  • TULA plays a significant role in initiating T-cell apoptosis through a caspase-independent pathway.
  • TULA is a functional interactor of AIF, a key mediator of caspase-independent apoptosis.
  • TULA enhances AIF-mediated apoptosis, likely by promoting interactions with unidentified apoptotic co-factors.

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