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Identification of Mediators of T-cell Receptor Signaling via the Screening of Chemical Inhibitor Libraries
08:49

Identification of Mediators of T-cell Receptor Signaling via the Screening of Chemical Inhibitor Libraries

Published on: January 22, 2019

8.9K

Fbw7 targets GATA3 through cyclin-dependent kinase 2-dependent proteolysis and contributes to regulation of T-cell

Kyoko Kitagawa, Kiyoshi Shibata, Akinobu Matsumoto

    Molecular and Cellular Biology
    |May 14, 2014
    PubMed

    Insights

    F-box protein Fbw7 regulates T-cell development by targeting GATA3 for degradation. This mechanism, involving cyclin-dependent kinase 2 (CDK2) phosphorylation, ensures proper T-cell differentiation and prevents apoptosis.

    Area of Science:

    • Immunology
    • Molecular Biology
    • Cell Biology

    Background:

    • Proper T-cell development requires precise regulation of lineage-specific transcription factors.
    • F-box protein 7 (Fbw7) is an E3 ubiquitin ligase involved in protein degradation.
    • GATA3 is a key transcription factor crucial for T-cell differentiation.

    Purpose of the Study:

    • To investigate the role of Fbw7 in T-cell development.
    • To determine if Fbw7 regulates GATA3 during T-cell differentiation.
    • To elucidate the mechanism of Fbw7-mediated GATA3 regulation.

    Main Methods:

    • Conditional inactivation of Fbw7 in mouse T-cell development.
    • Analysis of T-cell populations (CD4 SP, CD8 SP, DN) in Fbw7-deficient mice.
    • In vitro ubiquitylation and degradation assays using overexpressed proteins.
    • Identification of GATA3 phosphorylation sites and interacting kinases.
    • Detection of GATA3 phosphorylation in mouse thymocytes.

    Main Results:

    • Fbw7 deficiency led to reduced CD4 SP and altered CD8 SP cell proportions, with increased apoptosis in CD8 SP cells.
    • GATA3 levels were augmented in Fbw7-deficient thymocytes.
    • Fbw7 directly bound to, ubiquitylated, and destabilized GATA3.
    • Phosphorylation of GATA3 at Thr-156 within a Cdc4 phosphodegron (CPD) motif was essential for Fbw7-mediated degradation.
    • Cyclin-dependent kinase 2 (CDK2) was identified as the kinase responsible for GATA3 Thr-156 phosphorylation.

    Conclusions:

    • Fbw7-mediated degradation of GATA3 is a critical regulatory mechanism in T-cell development.
    • CDK2-dependent phosphorylation of GATA3 at Thr-156 targets it for Fbw7-mediated ubiquitylation and subsequent degradation.
    • This pathway ensures precise T-cell lineage differentiation and homeostasis.

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