The Cdc42 Effector Kinase PAK4 Localizes to Cell-Cell Junctions and Contributes to Establishing Cell Polarity

PLoS One. 2015 Jun 11;10(6):e0129634. doi: 10.1371/journal.pone.0129634. eCollection 2015.

Abstract

The serine/threonine kinase PAK4 is a Cdc42 effector whose role is not well understood; overexpression of PAK4 has been associated with some cancers, and there are reports that correlate kinase level with increased cell migration in vitro. Here we report that PAK4 is primarily associated with cell-cell junctions in all the cell lines we tested, and fails to accumulate at focal adhesions or at the leading edge of migrating cells. In U2OS osteosarcoma and MCF-7 breast cancer cell lines, PAK4 depletion did not affect collective cell migration, but affected cell polarization. By contrast, Cdc42 depletion (as reported by many studies) caused a strong defect in junctional assembly in multiple cells lines. We also report that the depletion of PAK4 protein or treatment of cells with the PAK4 inhibitor PF-3758309 can lead to defects in centrosome reorientation (polarization) after cell monolayer wounding. These experiments are consistent with PAK4 forming part of a conserved cell-cell junctional polarity Cdc42 complex. We also confirm β-catenin as a target for PAK4 in these cells. Treatment of cells with PF-3758309 caused inhibition of β-catenin Ser-675 phosphorylation, which is located predominantly at cell-cell junctions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line, Tumor / drug effects
  • Cell Polarity* / drug effects
  • Gene Knockdown Techniques
  • Humans
  • Intercellular Junctions / drug effects
  • Intercellular Junctions / metabolism*
  • MCF-7 Cells / drug effects
  • Phosphorylation
  • Protein Kinase Inhibitors / pharmacology
  • Pyrazoles / pharmacology
  • Pyrroles / pharmacology
  • Serine / metabolism
  • beta Catenin / metabolism
  • cdc42 GTP-Binding Protein / genetics
  • cdc42 GTP-Binding Protein / metabolism*
  • p21-Activated Kinases / antagonists & inhibitors
  • p21-Activated Kinases / genetics
  • p21-Activated Kinases / metabolism*

Substances

  • CTNNB1 protein, human
  • PF 3758309
  • Protein Kinase Inhibitors
  • Pyrazoles
  • Pyrroles
  • beta Catenin
  • Serine
  • PAK4 protein, human
  • p21-Activated Kinases
  • cdc42 GTP-Binding Protein

Grant support

This work was supported by the GSK-IMCB Research fund. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.