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Modulation of DRAK2 autophosphorylation by antigen receptor signaling in primary lymphocytes

Monica L Friedrich1, Meng Cui2, Jeniffer B Hernandez1

  • 1Center for Immunology and Department of Molecular Biology & Biochemistry, University of California, Irvine, Irvine, California 92697.

The Journal of Biological Chemistry
|December 22, 2006
PubMed

Insights

Death-associated protein-related apoptotic kinase-2 (DRAK2) activity is regulated by calcium signaling. Serine 12 phosphorylation of DRAK2, induced by antigen receptor stimulation, is crucial for its role in suppressing T cell activation.

Area of Science:

  • Immunology
  • Molecular Biology
  • Cell Signaling

Background:

  • Death-associated protein-related apoptotic kinase-2 (DRAK2) is a serine/threonine kinase highly expressed in lymphoid organs.
  • DRAK2 functions as a negative regulator of T cell activation.

Purpose of the Study:

  • To investigate the regulation of DRAK2 activity in primary lymphocytes.
  • To identify key regulatory sites of DRAK2 autophosphorylation.

Main Methods:

  • Mass spectrometry was used to identify autophosphorylation sites on DRAK2.
  • A phospho-specific antibody against Serine 12 (Ser12) was employed to detect phosphorylation.
  • Experiments involved antigen receptor stimulation, calcium mobilization inhibitors (BAPTA-AM), and SERCA inhibitors (thapsigargin) in T and B cells.

Main Results:

  • A key autophosphorylation site on DRAK2 was identified at Serine 12.
  • Antigen receptor stimulation rapidly induced Ser12 phosphorylation in T and B lymphocytes.
  • DRAK2 phosphorylation at Ser12 was dependent on intracellular calcium levels.
  • Calcium mobilization enhanced DRAK2 kinase activity, while its inhibition blocked it.

Conclusions:

  • DRAK2 kinase activity is regulated in a calcium-dependent manner.
  • Phosphorylation of DRAK2 at Ser12 is essential for its optimal suppression of T cell activation.
  • A feedback loop involving calcium signaling may modulate DRAK2 activity following antigen receptor signaling.

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