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NKX3.1 is regulated by protein kinase CK2 in prostate tumor cells

Xiang Li1, Bin Guan, Sam Maghami

  • 1Department of Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.

Molecular and Cellular Biology
|April 4, 2006
PubMed

Insights

Protein kinase CK2 phosphorylates NKX3.1 at Thr89 and Thr93, impacting its stability in prostate cancer cells. This phosphorylation by CK2alpha

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Biochemistry

Background:

  • Diminished NKX3.1 expression correlates with prostate cancer progression.
  • NKX3.1's amino acid sequence contains potential phosphorylation sites for CK2.
  • Understanding NKX3.1 post-translational regulation is crucial for prostate cancer research.

Purpose of the Study:

  • To investigate the post-translational regulation of NKX3.1 by protein kinase CK2.
  • To determine the specific sites of NKX3.1 phosphorylation by CK2.
  • To elucidate the role of CK2 in NKX3.1 stability and accumulation in prostate cancer cells.

Main Methods:

  • In vitro kinase assays and mass spectrometry to identify phosphorylation sites.
  • Pharmacological inhibition of CK2 (apigenin, 5,6-dichlorobenzimidazole riboside) in LNCaP cells.
  • Site-directed mutagenesis (Thr89/93 to alanine) and small interfering RNA (siRNA) knockdown of CK2 subunits.
  • Proteasome inhibition and Western blot analysis to assess protein stability and levels.

Main Results:

  • CK2 directly phosphorylates recombinant NKX3.1 at Thr89 and Thr93.
  • CK2 inhibition decreases NKX3.1 accumulation, which is rescued by proteasome inhibition.
  • Mutating Thr89 and Thr93 to alanine reduces NKX3.1 stability in vivo.
  • siRNA knockdown of CK2alpha' reduces NKX3.1 levels, unlike CK2alpha knockdown.
  • Free CK2alpha' phosphorylates NKX3.1, but CK2alpha' liberated from the holoenzyme does not.

Conclusions:

  • CK2 acts as a significant regulator of NKX3.1 in prostate tumor cells.
  • Phosphorylation of NKX3.1 by CK2 influences its stability and accumulation.
  • Evidence suggests functionally distinct pools of CK2alpha' in LNCaP cells.

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