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A novel pathway down-modulating T cell activation involves HPK-1-dependent recruitment of 14-3-3 proteins on SLP-76

Vincenzo Di Bartolo1, Benjamin Montagne, Mogjiborahman Salek

  • 1Molecular Immunology Unit, Centre National de la Recherche Scientifique (CNRS) URA 1961, Institut Pasteur, 75724 Paris, Cedex 15, France. vbartolo@pasteur.fr

The Journal of Experimental Medicine
|March 14, 2007
PubMed

Insights

14-3-3 proteins bind to SLP-76, a key T cell receptor signaling molecule, after T cell activation. This interaction, regulated by HPK-1 kinase, tunes T cell responses.

Area of Science:

  • Immunology
  • Molecular Biology
  • Cell Signaling

Background:

  • SH2 domain-containing leukocyte protein of 76 kD (SLP-76) is crucial for T cell receptor (TCR)-mediated activation.
  • Understanding the regulation of SLP-76 function is vital for controlling T cell responses.

Purpose of the Study:

  • To identify novel binding partners of SLP-76.
  • To elucidate the regulatory mechanisms of SLP-76 during T cell activation.
  • To investigate the role of hematopoietic progenitor kinase 1 (HPK-1) in SLP-76 regulation.

Main Methods:

  • Co-immunoprecipitation to identify SLP-76 binding partners.
  • Site-directed mutagenesis (S376A) to study the role of serine 376 phosphorylation.
  • RNA interference (siRNA) to knockdown HPK-1.
  • In vitro kinase assays.
  • Analysis of downstream signaling events like tyrosine phosphorylation and gene transcription.

Main Results:

  • 14-3-3epsilon and zeta proteins were identified as novel SLP-76 binding partners.
  • Binding is induced by TCR ligation and dependent on SLP-76 phosphorylation at serine 376.
  • HPK-1 directly phosphorylates SLP-76 at serine 376.
  • S376A mutation or HPK-1 knockdown enhances TCR-induced tyrosine phosphorylation of SLP-76 and phospholipase C-gamma1.
  • SLP-76-S376A mutant shows increased interleukin 2 gene transcription.

Conclusions:

  • A novel negative feedback loop regulates T cell activation.
  • HPK-1-dependent phosphorylation of SLP-76 at serine 376 leads to 14-3-3 protein recruitment.
  • This mechanism fine-tunes T cell activation by modulating SLP-76 signaling efficacy.

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