Anti-apoptotic Action of Wnt5a in Dermal Fibroblasts Is Mediated by the PKA Signaling Pathways

Cell Signal. 2008 Jul;20(7):1256-66. doi: 10.1016/j.cellsig.2008.02.013. Epub 2008 Feb 26.

Abstract

Wnts are secreted glycoproteins that control diverse biological processes, such as proliferation, differentiation, and apoptosis. We here found that Wnt5a inhibited apoptosis induced by serum deprivation in primary-cultured human dermal fibroblasts. Anti-apoptotic activity of Wnt5a was not inhibited by a dickkopf-1 (DKK), which blocks the canonical Wnt pathway. On the other hand, loss of function of protein kinase A (PKA), induced by treatment with PKA inhibitors, siRNA-mediated knocking down of endogenous PKA catalytic subunits, or enforced expression of dominant-negative PKA inhibited the Wnt5a anti-apoptotic activity, indicating the involvement of PKA in the Wnt5a anti-apoptotic activity. In agreement, phosphorylation levels of a cAMP response element binding protein (CREB), a representative downstream effector of PKA, the activation of which is known to lead to the pro-survival effects, was elevated by Wnt5a. In addition, Wnt5a increased the nuclear beta-catenin level and treatment with imatinib or ionomycin, either of which blocks the beta-catenin pathway, reduced the anti-apoptotic activity of Wnt5a, together suggesting the simultaneous involvement of the beta-catenin-mediated pathway in the Wnt5a anti-apoptotic activity. Based on another finding indicating that Wnt5a upregulated PKA-mediated phosphorylation of glycogen synthase kinase-3beta (GSK-3beta) at serine 9 that caused inactivation of GSK-3beta and subsequently resulted in activation of the beta-catenin pathway, we have speculated that the Wnt5a anti-apoptotic activity may be partially mediated by PKA-mediated phosphorylation of GSK-3beta and subsequent activation of the beta-catenin pathway.

MeSH terms

  • Apoptosis / drug effects*
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • Dermis / cytology*
  • Dermis / enzymology
  • Enzyme Activation / drug effects
  • Fibroblasts / cytology*
  • Fibroblasts / drug effects
  • Fibroblasts / enzymology*
  • Glycogen Synthase Kinase 3 / metabolism
  • Glycogen Synthase Kinase 3 beta
  • Humans
  • LDL-Receptor Related Proteins / metabolism
  • Low Density Lipoprotein Receptor-Related Protein-5
  • Low Density Lipoprotein Receptor-Related Protein-6
  • Models, Biological
  • Phosphorylation / drug effects
  • Phosphoserine / metabolism
  • Receptors, LDL / metabolism
  • Signal Transduction / drug effects*
  • Wnt Proteins / pharmacology*
  • beta Catenin / metabolism

Substances

  • LDL-Receptor Related Proteins
  • LRP5 protein, human
  • LRP6 protein, human
  • Low Density Lipoprotein Receptor-Related Protein-5
  • Low Density Lipoprotein Receptor-Related Protein-6
  • Receptors, LDL
  • Wnt Proteins
  • beta Catenin
  • Phosphoserine
  • GSK3B protein, human
  • Glycogen Synthase Kinase 3 beta
  • Cyclic AMP-Dependent Protein Kinases
  • Glycogen Synthase Kinase 3