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Suppression of cyclic GMP-dependent protein kinase is essential to the Wnt/cGMP/Ca2+ pathway

Li Ma1, Hsien-yu Wang

  • 1Department of Pharmacology, Diabetes and Metabolic Diseases Research Center, School of Medicine, State University of New York, Stony Brook, New York 11794-8661, USA.

The Journal of Biological Chemistry
|August 22, 2006
PubMed

Insights

The Wnt/Frizzled-2 pathway regulates intracellular calcium (Ca2+) and cyclic GMP (cGMP) levels. Protein kinase G acts as a key effector, influencing NF-AT transcription and Ca2+ signaling.

Area of Science:

  • Cellular signaling pathways
  • Molecular biology
  • Calcium and cyclic GMP regulation

Background:

  • The Wnt signaling pathway plays crucial roles in development and disease.
  • Specific downstream effectors of the noncanonical Wnt/Frizzled-2 pathway remain incompletely understood.
  • Intracellular calcium (Ca2+) and cyclic guanosine monophosphate (cGMP) are critical second messengers.

Purpose of the Study:

  • To identify novel downstream effectors of the Wnt/Frizzled-2 pathway.
  • To elucidate the roles of Ca2+ and cGMP in Wnt/Frizzled-2 signaling.
  • To investigate the function of protein kinase G (PKG) in this pathway.

Main Methods:

  • Pertussis toxin treatment to assess G protein involvement.
  • Gene silencing (knock-down) of Galphat2 and Galphao.
  • Pharmacological modulation of cGMP levels (inhibition of phosphodiesterase, addition of 8-bromocyclic GMP).
  • Chemical inhibition of PKG using Rp-8-pCPT-cGMP.
  • Measurement of NF-AT-dependent transcription and intracellular Ca2+ mobilization.

Main Results:

  • Wnt/Frizzled-2 activation suppressed PKG activity and activated NF-AT transcription.
  • These effects were dependent on Galphat2/Galphao and sensitive to pertussis toxin.
  • Elevated cGMP activated PKG, inhibited Ca2+ mobilization, and attenuated Wnt5a-induced NF-AT activation.
  • PKG inhibition increased NF-AT transcription and Ca2+ mobilization without Wnt stimulation.

Conclusions:

  • Protein kinase G is a critical downstream effector of the noncanonical Wnt-Frizzled-2 pathway.
  • The pathway involves a cGMP/Ca2+ signaling cascade.
  • PKG modulates NF-AT-dependent transcription and Ca2+ dynamics in response to Wnt stimulation.

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