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Phosphorylation of SET protein at Ser171 by protein kinase D2 diminishes its inhibitory effect on protein phosphatase

Atsushi Irie1, Kumiko Harada, Norie Araki

  • 1Department of Immunogenetics, Graduate School of Medical Sciences, Kumamoto University, Honjo, Kumamoto, Japan.

Plos One
|December 20, 2012
PubMed

Insights

Protein kinase D2 (PKD2) regulates T cell activity by phosphorylating the SET protein at Ser171. This phosphorylation reduces SET

Area of Science:

  • Immunology
  • Cell Biology
  • Biochemistry

Background:

  • Protein kinase D2 (PKD2) is activated upon T-cell receptor (TCR) stimulation.
  • PKD2 influences interleukin-2 promoter activation and T cell death.
  • SET protein is a known inhibitor of protein phosphatase 2A (PP2A).

Purpose of the Study:

  • To identify the specific amino acid residues on SET protein phosphorylated by PKD2.
  • To determine the impact of SET phosphorylation on PP2A activity.
  • To elucidate the role of PKD2 in regulating PP2A activity in T cells.

Main Methods:

  • In vitro kinase assays using recombinant SET mutants (Ser/Thr to Ala substitutions).
  • Phosphorylation-mimic SET mutant (Ser171 to Glu) analysis.
  • RNA interference (RNAi) knockdown of PKD2 in Jurkat cells.
  • PKD2 inhibitor (Gö6976) treatment of human CD4+ T cells.
  • Assessment of PP2A activity via phosphorylation status of its catalytic subunit (Tyr307).

Main Results:

  • Serine 171 (Ser171) of SET was identified as a phosphorylation site by PKD2.
  • Phosphorylation-mimic substitution (Ser171 to Glu) in SET reduced its inhibition of PP2A activity.
  • PKD2 knockdown or inhibition led to decreased PP2A activity in activated T cells.
  • These findings link PKD2-mediated SET phosphorylation to PP2A regulation.

Conclusions:

  • PKD2 directly phosphorylates SET protein at Ser171.
  • Phosphorylation of SET by PKD2 modulates PP2A phosphatase activity.
  • PKD2 plays a crucial role in regulating PP2A activity within activated T cells via SET phosphorylation.

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