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Characterization at the Molecular Level using Robust Biochemical Approaches of a New Kinase Protein
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Characterization at the Molecular Level using Robust Biochemical Approaches of a New Kinase Protein

Published on: June 30, 2019

Characterization of S6K2, a novel kinase homologous to S6K1

K K Lee-Fruman1, C J Kuo, J Lippincott

  • 1Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, MA 02115, USA.

Oncogene
|September 22, 1999
PubMed

Insights

Researchers identified a new protein kinase, S6K2, which is inhibited by rapamycin and may play a role in cellular proliferation and translational control, similar to S6K1.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Rapamycin is an immunosuppressant that inhibits mTOR, a key regulator of cellular proliferation.
  • The mTOR:FKBP12:rapamycin complex inhibits cell cycle progression by targeting downstream proteins like p70S6k1 (S6K1).
  • S6K1 phosphorylates ribosomal protein S6, influencing translational control.

Purpose of the Study:

  • To clone and characterize a novel homolog of S6K1, named p54 S6 kinase 2 (p54S6k2/S6K2).
  • To investigate the regulation and function of S6K2 in relation to S6K1 and mTOR signaling.
  • To explore the potential role of S6K2 in S6 phosphorylation and translational control.

Main Methods:

  • Cloning and characterization of the S6K2 gene and protein.
  • Assessing S6K2 activation by mitogens, PI3K, and PDK1.
  • Evaluating the effect of rapamycin and wortmannin on S6K2 activity.
  • Analyzing S6K2 activity and S6 phosphorylation in S6K1 knockout (S6K1-/-) ES cells.
  • Determining the cellular localization of different S6K2 isoforms.

Main Results:

  • A novel S6K1 homolog, S6K2, was cloned and characterized.
  • S6K2 activation is stimulated by mitogens and PI3K, and inhibited by rapamycin and wortmannin.
  • Differences in PDK1 activation suggest distinct regulatory mechanisms for S6K1 and S6K2.
  • S6K2 activity and S6 phosphorylation were observed in S6K1-/- ES cells, indicating S6K2's role in in vivo S6 phosphorylation.
  • Two S6K2 isoforms with distinct subcellular localizations (soluble and particulate) were identified.

Conclusions:

  • The study demonstrates the existence of a family of rapamycin-sensitive protein kinases, including S6K1 and S6K2.
  • S6K2 is a functional homolog of S6K1 and may contribute to S6 phosphorylation and translational control.
  • Distinct isoforms and regulatory differences suggest complex roles for S6K2 in mTOR signaling pathways.

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