Frizzled-5 receptor is involved in neuronal polarity and morphogenesis of hippocampal neurons

PLoS One. 2013 Oct 18;8(10):e78892. doi: 10.1371/journal.pone.0078892. eCollection 2013.

Abstract

The Wnt signaling pathway plays important roles during different stages of neuronal development, including neuronal polarization and dendritic and axonal outgrowth. However, little is known about the identity of the Frizzled receptors mediating these processes. In the present study, we investigated the role of Frizzled-5 (Fzd5) on neuronal development in cultured Sprague-Dawley rat hippocampal neurons. We found that Fzd5 is expressed early in cultured neurons on actin-rich structures localized at minor neurites and axonal growth cones. At 4 DIV, Fzd5 polarizes towards the axon, where its expression is detected mainly at the peripheral zone of axonal growth cones, with no obvious staining at dendrites; suggesting a role of Fzd5 in neuronal polarization. Overexpression of Fzd5 during the acquisition of neuronal polarity induces mislocalization of the receptor and a loss of polarized axonal markers. Fzd5 knock-down leads to loss of axonal proteins, suggesting an impaired neuronal polarity. In contrast, overexpression of Fzd5 in neurons that are already polarized did not alter polarity, but decreased the total length of axons and increased total dendrite length and arborization. Fzd5 activated JNK in HEK293 cells and the effects triggered by Fzd5 overexpression in neurons were partially prevented by inhibition of JNK, suggesting that a non-canonical Wnt signaling mechanism might be involved. Our results suggest that, Fzd5 has a role in the establishment of neuronal polarity, and in the morphogenesis of neuronal processes, in part through the activation of the non-canonical Wnt mechanism involving JNK.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Polarity* / drug effects
  • Cell Shape*
  • Frizzled Receptors / genetics
  • Frizzled Receptors / metabolism*
  • Gene Expression Regulation, Developmental
  • HEK293 Cells
  • Hippocampus / cytology*
  • Humans
  • JNK Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • Neurons / cytology*
  • Neurons / drug effects
  • PC12 Cells
  • Protein Kinase Inhibitors / pharmacology
  • Rats
  • Rats, Sprague-Dawley

Substances

  • Frizzled Receptors
  • Protein Kinase Inhibitors
  • JNK Mitogen-Activated Protein Kinases

Grants and funding

This work was supported by Basal Center of Excellence in Aging and Regeneration (CONICYT-PFB12/2007) and Fondecyt (1120156) to N.C.I., Predoctoral Fellowships from CONICYT to P.G.S and V.T.R, Fondecyt (11110012) and Insertion of Postdoctoral Researchers in the Academy-CONICYT (N°79090027) to LV-N. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.