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Regulation of the AMPK-related protein kinases by ubiquitination

David M Thomson1, Marc D H Hansen, William W Winder

  • 1Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT 84602, USA.

The Biochemical Journal
|March 28, 2008
PubMed

Insights

Deubiquitination regulates AMP-activated protein kinase (AMPK)-related kinases. USP9X deubiquitinates NUAK1 and MARK4, controlling their phosphorylation and activation via unique ubiquitin chains.

Area of Science:

  • Cellular signaling pathways
  • Protein regulation and modification
  • Kinase signaling networks

Background:

  • AMP-activated protein kinase (AMPK) and related kinases are crucial for cellular energy homeostasis and signaling.
  • LKB1 is a master kinase that phosphorylates numerous substrates, raising questions about signal specificity.
  • Regulation of kinase activity is essential for preventing aberrant signaling and maintaining cellular function.

Purpose of the Study:

  • To investigate the role of deubiquitination in regulating the activity of AMPK-related kinases.
  • To elucidate the mechanism by which signal transduction specificity is achieved at the kinase substrate level.
  • To identify specific ubiquitin chain linkages involved in kinase regulation.

Main Methods:

  • In vivo polyubiquitination assays to detect ubiquitination of AMPK-related kinases.
  • Enzymatic assays using the deubiquitinating enzyme USP9X.
  • Analysis of different polyubiquitin chain linkages (Lys29/Lys33 vs. Lys48/Lys63).

Main Results:

  • NUAK1 and MARK4, members of the AMPK-related kinase family, were found to be polyubiquitinated in vivo.
  • The deubiquitinating enzyme USP9X was identified as a regulator of NUAK1 and MARK4 ubiquitination.
  • Evidence was provided for the regulation of these kinases by unusual Lys(29)/Lys(33) polyubiquitin chains, distinct from common linkages.

Conclusions:

  • Deubiquitination by USP9X plays a critical role in controlling the phosphorylation and activation of specific AMPK-related kinases.
  • The use of unusual polyubiquitin chain linkages (Lys29/Lys33) represents a novel mechanism for conferring specificity in kinase signaling.
  • This finding sheds light on how master kinases achieve substrate selectivity and how these pathways are regulated.

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