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Protein kinase Czeta phosphorylates nuclear factor of activated T cells and regulates its transactivating activity

Belén San-Antonio1, Miguel A Iñiguez, Manuel Fresno

  • 1Centro de Biologia Molecular, Consejo Superior de Investigaciones Cientificas, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid, Spain.

The Journal of Biological Chemistry
|May 22, 2002
PubMed

Insights

Protein kinase C zeta (PKCzeta) enhances T cell activation by modulating the transcription factor NFAT. This study reveals PKCzeta directly interacts with and phosphorylates NFAT, controlling its transactivation domain activity.

Area of Science:

  • Immunology
  • Molecular Biology
  • Cell Signaling

Background:

  • Protein kinase C (PKC) isoforms are crucial for T lymphocyte activation.
  • The specific role and mechanism of PKCzeta in T cell activation remain largely uncharacterized.

Purpose of the Study:

  • To investigate the function of PKCzeta in T cell activation.
  • To elucidate the molecular mechanisms by which PKCzeta influences T cell signaling pathways.

Main Methods:

  • Generation of Jurkat T cell transfectants expressing wild-type or kinase-dead PKCzeta.
  • Assays for transcriptional activation mediated by NF-kappaB and NFAT.
  • Analysis of NFAT nuclear translocation and DNA binding.
  • Co-precipitation and in vitro phosphorylation assays.

Main Results:

  • PKCzeta expression, unlike its kinase-dead mutant, significantly increased transcriptional activation via NF-kappaB and NFAT.
  • PKCzeta enhanced NFAT-mediated transcription without affecting NFAT nuclear translocation or DNA binding.
  • PKCzeta physically interacted with NFAT1 and NFAT2 and phosphorylated NFAT1.
  • PKCzeta synergized with calcineurin to activate the NFAT1 transactivation domain.

Conclusions:

  • PKCzeta plays a critical role in T cell activation.
  • PKCzeta modulates NFAT function by directly interacting with and phosphorylating its transactivation domain.
  • This provides a novel mechanism for regulating T cell transcriptional responses.

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