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Nuclear export of S6K1 II is regulated by protein kinase CK2 phosphorylation at Ser-17

Ganna Panasyuk1, Ivan Nemazanyy, Alexander Zhyvoloup

  • 1Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, Kyiv 03143, Ukraine.

The Journal of Biological Chemistry
|August 10, 2006
PubMed

Insights

Protein kinase CK2 (CK2) phosphorylates Ribosomal S6 kinase 1 variant II (S6K1 II) at Ser-17, enhancing its nuclear export. This reveals a novel regulatory mechanism for S6K1 II localization and function in cell signaling.

Area of Science:

  • Cellular signaling
  • Molecular biology
  • Biochemistry

Background:

  • Ribosomal S6 kinases (S6Ks) regulate cell growth and metabolism.
  • S6K activation involves PI3K/mTOR pathways, with cytoplasmic and nuclear variants like S6K1 II.
  • Nuclear-cytoplasmic shuttling of S6Ks is induced by mitogenic stimuli.

Purpose of the Study:

  • Identify novel binding and regulatory partners for S6K1 II.
  • Investigate the role of protein kinase CK2 (CK2) in S6K1 II regulation.
  • Elucidate the mechanism of S6K1 II nuclear export.

Main Methods:

  • Yeast two-hybrid screening to identify protein interactions.
  • Co-immunoprecipitation to confirm S6K1 II and CK2 interaction.
  • Site-directed mutagenesis and phosphospecific antibodies to analyze phosphorylation.
  • Cellular localization studies using microscopy and leptomycin B treatment.

Main Results:

  • CK2 directly binds to and phosphorylates S6K1 II at Ser-17.
  • Phosphorylation of Ser-17 by CK2 enhances S6K1 II nuclear export.
  • The S17E mutant (phosphorylation mimic) shows increased nuclear export.
  • Nuclear export of S6K1 is mediated by a CRM1-dependent mechanism.

Conclusions:

  • CK2 is a novel regulatory partner of S6K1 II.
  • CK2-mediated phosphorylation of Ser-17 regulates S6K1 II nuclear export.
  • This interaction establishes a functional link between CK2 and S6K signaling pathways.

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