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Regulation of anchorage-dependent signal transduction by protein kinase A and p21-activated kinase

A K Howe1, R L Juliano

  • 1Department of Pharmacology, University of North Carolina at Chapel Hill, North Carolina 27599-7365, USA. alanhowe@med.unc.edu

Nature Cell Biology
|September 12, 2000
PubMed

Insights

Inhibition of cAMP-dependent protein kinase (PKA) enables growth factor signaling in non-adherent cells, revealing PKA and p21-activated kinase (PAK) as key regulators of anchorage-dependent cell signaling.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Signal Transduction

Background:

  • Mitogen-activated protein kinase (MAPK) cascade activation is blocked in non-adherent cells and when cAMP-dependent protein kinase (PKA) is active.
  • Understanding anchorage-dependent signaling is crucial for cell growth and survival.

Purpose of the Study:

  • To investigate the role of PKA and p21-activated kinase (PAK) in regulating anchorage-independent MAPK signaling.
  • To elucidate the mechanisms underlying signal transduction in non-adherent cells.

Main Methods:

  • Inhibition of PKA in non-adherent cells.
  • Assessment of MAPK cascade stimulation by growth factors.
  • Analysis of paxillin and focal-adhesion kinase (FAK) tyrosine phosphorylation.
  • Use of cytochalasin D to probe the role of the actin cytoskeleton.
  • Manipulation of p21-activated kinase (PAK) activity (dominant-negative and constitutively active forms).

Main Results:

  • Inhibition of PKA permits transient, anchorage-independent MAPK signaling by growth factors.
  • Sustained tyrosine phosphorylation of paxillin and FAK correlates with this signaling.
  • The actin cytoskeleton is implicated in mediating this anchorage-independent signaling.
  • Constitutively active PAK also enables anchorage-independent MAPK signaling.
  • PKA negatively regulates PAK; PKA inhibition's effect on signaling is modulated by PAK activity.

Conclusions:

  • PKA and PAK are critical negative and positive regulators, respectively, of anchorage-dependent signal transduction.
  • The interplay between PKA and PAK influences MAPK cascade activation in non-adherent cells.
  • Actin cytoskeleton dynamics play a role in mediating anchorage-independent signaling pathways.

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