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Protein kinase D-mediated phosphorylation at Ser99 regulates localization of p21-activated kinase 4

Ligia I Bastea1, Heike Döppler, Sarah E Pearce

  • 1*Department of Cancer Biology, Mayo Clinic Comprehensive Cancer Center, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL 32224, U.S.A.

The Biochemical Journal
|July 12, 2013
PubMed

Insights

Protein kinase D1 (PKD1) phosphorylates p21-activated kinase 4 (PAK4) at Ser99, enabling its leading-edge localization and facilitating directed cell migration through a PAK4-LIMK-PKD1 complex.

Area of Science:

  • Cell biology
  • Molecular biology
  • Biochemistry

Background:

  • p21-activated kinases (PAKs) are crucial RhoGTPase effectors involved in cell motility.
  • PAK4 regulates cofilin activity at the leading edge via LIMK activation, a process critical for cell migration.
  • PAK4 activity is modulated by RhoGTPase binding and phosphorylation at Ser474.

Purpose of the Study:

  • To elucidate the regulatory mechanisms of PAK4 localization and function in directed cell migration.
  • To investigate the role of novel phosphorylation sites on PAK4 regulation.
  • To identify kinases that mediate PAK4 phosphorylation and complex formation.

Main Methods:

  • Site-directed mutagenesis to investigate phosphorylation sites.
  • Immunoprecipitation assays to detect protein complex formation.
  • Cell migration assays to assess functional consequences.

Main Results:

  • Phosphorylation of PAK4 at Ser99 by protein kinase D1 (PKD1) is essential for its targeting to the leading edge of migrating cells.
  • Ser99 phosphorylation mediates the binding of PAK4 to 14-3-3 proteins.
  • A novel PAK4-LIMK-PKD1 complex is formed, regulating cofilin activity and directed cell migration.

Conclusions:

  • PKD1-mediated phosphorylation of PAK4 at Ser99 represents a new regulatory layer controlling PAK4 localization and function.
  • This phosphorylation event is critical for the assembly of a signaling complex that governs cofilin activity and cell migration.
  • The findings reveal a novel pathway for regulating directed cell migration involving PAK4, LIMK, and PKD1.

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