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CDK4 expression and activity are required for cytokine responsiveness in T cells

J F Modiano1, J Mayor, C Ball

  • 1Center for Cancer Causation and Prevention, AMC Cancer Research Center, Denver, CO 80214, USA. modianoj@amc.org

Journal of Immunology (Baltimore, Md. : 1950)
|December 20, 2000
PubMed

Insights

Cyclin-dependent kinase 4 (CDK4) is crucial for T cell responsiveness to interleukin-2 (IL-2). Its expression and activity are necessary for T cells to respond to cytokines, linking signaling to cell cycle progression.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Biology

Background:

  • T cell activation via the antigen (Ag) receptor can result in either cytokine responsiveness or unresponsiveness.
  • Interleukin-2 (IL-2) is a key cytokine for T cell proliferation and function.
  • Cyclin-dependent kinases (CDKs) regulate cell cycle progression and are implicated in various cellular processes.

Purpose of the Study:

  • To investigate the role of cyclin-dependent kinase 4 (CDK4) in establishing and maintaining IL-2 responsiveness in human T cells.
  • To determine the relationship between CDK4 expression/activity and T cell cytokine response.
  • To explore the impact of T cell receptor (TCR) stimulation on CDK4 activity and IL-2 responsiveness.

Main Methods:

  • Analysis of CDK4 expression and activity in peripheral blood T cells and the IL-2-dependent Kit-225 T cell line.
  • Stimulation of T cells using mitogens, IL-2, and TCR-activating agents (PHA, anti-CD3, PMA).
  • Assessment of T cell proliferation in response to IL-2.
  • Manipulation of CDK4 activity using inhibitors (herbimycin A, staurosporine) and overexpression of CDK inhibitors (p16/Ink4-a, p21/Waf-1a) or a kinase-inactive CDK4 mutant.

Main Results:

  • CDK4 expression and activity, sensitive to herbimycin A and staurosporine, precede IL-2 responsiveness in mitogen-stimulated T cells.
  • A subset of unstimulated T cells (~30%) exhibited constitutive CDK4 expression/activity and IL-2 responsiveness, resistant to inhibitors.
  • In Kit-225 cells, TCR stimulation reduced CDK4 expression/activity, leading to IL-2 unresponsiveness, which could be mimicked by CDK inhibitors or a dominant-negative CDK4 mutant.

Conclusions:

  • CDK4 expression and activity are essential for inducing and maintaining T cell responsiveness to cytokines like IL-2.
  • CDK4 acts as a critical link between T cell signaling pathways and the cell cycle machinery controlling proliferation.
  • Aberrant regulation of CDK4 may contribute to altered cytokine responsiveness in T cells.

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