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Programmed cell death protein 5 (PDCD5) is phosphorylated by CK2 in vitro and in 293T cells

Mauro Salvi1, Dong Xu, Yingyu Chen

  • 1Department of Biological Chemistry, University of Padova, Viale G. Colombo 3, Padua, Italy. mauro.salvi@unipd.it

Biochemical and Biophysical Research Communications
|July 21, 2009
PubMed

Insights

Protein kinase CK2 phosphorylates Programmed Cell Death 5 (PDCD5), enhancing its role in apoptosis. This CK2-PDCD5 interaction is crucial for programmed cell death, particularly under stress conditions like doxorubicin or UV exposure.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Protein kinase CK2 (CK2) is a key regulator of numerous cellular processes, including cell growth and apoptosis.
  • Programmed Cell Death 5 (PDCD5) is implicated in cell death pathways and is frequently downregulated in human tumors.
  • Previous phosphoproteomic analyses suggested PDCD5 as a potential substrate of CK2.

Purpose of the Study:

  • To experimentally validate Programmed Cell Death 5 (PDCD5) as a direct substrate of protein kinase CK2 (CK2).
  • To investigate the functional consequences of CK2-mediated PDCD5 phosphorylation on apoptosis.
  • To elucidate the role of CK2 phosphorylation at serine 118 (S118) in PDCD5's apoptotic function.

Main Methods:

  • In vitro kinase assays using purified CK2 subunits and holoenzyme.
  • In vivo phosphorylation studies in 293T cells.
  • Site-directed mutagenesis to create a non-phosphorylatable PDCD5 mutant (S118A).
  • Apoptosis assays in U2OS cells treated with doxorubicin or UV radiation.

Main Results:

  • PDCD5 is confirmed as a bona fide substrate of CK2, with phosphorylation occurring at S118 both in vitro and in vivo.
  • CK2 phosphorylates PDCD5 in human 293T cells.
  • Expression of the non-phosphorylatable PDCD5 mutant (S118A) significantly reduced the acceleration of doxorubicin- or UV-induced apoptosis.

Conclusions:

  • CK2 directly phosphorylates PDCD5 at S118, establishing a functional link between CK2 activity and PDCD5's pro-apoptotic function.
  • CK2-mediated phosphorylation of PDCD5 is essential for its full contribution to apoptosis induction.
  • These findings highlight a novel regulatory mechanism controlling apoptosis via the CK2-PDCD5 axis.

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