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Identification of the atypical MAPK Erk3 as a novel substrate for p21-activated kinase (Pak) activity

Alina De la Mota-Peynado1, Jonathan Chernoff, Alexander Beeser

  • 1Division of Biology and Molecular, Cellular, and Developmental Biology Program, Kansas State University, Manhattan, Kansas 66506, USA.

The Journal of Biological Chemistry
|February 15, 2011
PubMed

Insights

Class I p21-activated kinases (Pak1-3) phosphorylate Erk3, a novel substrate. Pak kinase activity influences Erk3 nuclear accumulation and signaling, advancing understanding of atypical MAPK pathways.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Kinase Biology

Background:

  • Class I p21-activated kinases (Pak1-3) are crucial regulators of fundamental cellular processes.
  • Identifying novel kinase substrates is essential for understanding kinase function and signaling pathways.
  • Mitogen-activated protein kinase (MAPK) signaling cascades involve numerous protein interactions and regulatory mechanisms.

Purpose of the Study:

  • To identify novel substrates of class I Pak kinases.
  • To investigate the functional consequences of Pak-mediated phosphorylation of its substrates.
  • To elucidate the role of Pak kinase activity in atypical MAPK signaling.

Main Methods:

  • High-density protein microarrays were screened using recombinant Pak2 to identify potential substrates.
  • In vitro kinase assays with recombinant Erk3 were performed to confirm phosphorylation.
  • Phospho-specific antibodies were used to identify the phosphorylation site on Erk3.
  • Cell-based assays were conducted to assess the impact of Pak inhibition on Erk3 localization and phosphorylation.

Main Results:

  • The atypical MAPK Erk3 was identified as a potential Pak2 substrate via protein microarray screening.
  • In vitro kinase assays confirmed that Pak2 directly phosphorylates Erk3 at serine 189 in its activation loop.
  • Inhibition of class I Pak kinase activity in cells led to increased nuclear accumulation of Erk3.
  • Pak inhibition also reduced Erk3 phosphorylation at Ser(189) and impaired Erk3-Prak complex formation.

Conclusions:

  • Erk3 is a novel substrate of class I Pak kinases.
  • Pak kinase activity plays a role in regulating Erk3's subcellular localization and signaling.
  • These findings suggest a functional link between Pak kinases and atypical MAPK signaling pathways.

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