Inhibition of Cdk2 activation by selected tyrphostins causes cell cycle arrest at late G1 and S phase

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Development of Inhibitors of Protein-protein Interactions through REPLACE: Application to the Design and Development Non-ATP Competitive CDK Inhibitors
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Development of Inhibitors of Protein-protein Interactions through REPLACE: Application to the Design and Development Non-ATP Competitive CDK Inhibitors

Published on: October 26, 2015

N Kleinberger-Doron1, N Shelah, R Capone

  • 1Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel.

Experimental Cell Research
|June 25, 1998
PubMed

Insights

Certain tyrphostins block cell proliferation by inhibiting cyclin-dependent kinase 2 (Cdk2) activation. These compounds arrest cells in the G1/S phase, representing a new class of cell proliferation blockers targeting Cdk2 activation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Tyrphostins previously shown to inhibit epidermal growth factor receptor (EGF-R) phosphorylation in cell-free systems were found to inhibit EGF- and calf serum-induced cell growth and DNA synthesis in intact cells.
  • These tyrphostins retain inhibitory activity even when added after the restriction point, when receptor activation is no longer required for cell cycle progression.

Purpose of the Study:

  • To investigate the mechanism by which specific tyrphostins inhibit cell growth and DNA synthesis.
  • To identify the molecular target and understand the structure-activity relationship of these novel cell proliferation blockers.

Main Methods:

  • Cell cycle analysis using flow cytometry to determine cell cycle arrest points.
  • Biochemical assays to assess enzyme activity, protein levels, and protein-protein interactions.
  • Structure-activity relationship (SAR) studies to define the pharmacophore.

Main Results:

  • Tyrphostins AG555 and AG556 arrested 85% of cells at late G1, while AG490 and AG494 caused arrest at late G1 and during S phase. No G2 or M phase arrest was observed.
  • These tyrphostins inhibit the activation of cyclin-dependent kinase 2 (Cdk2) without affecting its levels, intrinsic kinase activity, or association with cyclins (E, A) or inhibitors (p21, p27).
  • The compounds did not affect Cdk2 activating kinase (CAK) or cdc25 phosphatase activity, but led to the accumulation of tyrosine 15-phosphorylated Cdk2, indicating inhibition of Cdk2 activation and subsequent G1/S cell cycle arrest.

Conclusions:

  • The studied tyrphostins represent a new class of cell proliferation blockers targeting Cdk2 activation.
  • The precise pharmacophore identified suggests a novel molecular target involved in regulating the tyrosine-phosphorylated state of Cdk2.
  • These findings provide a basis for developing new therapeutic strategies targeting cell cycle regulation in proliferative diseases.

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