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Myosin light chains are not a physiological substrate of AMPK in the control of cell structure changes

Laurent Bultot1, Sandrine Horman, Dietbert Neumann

  • 1Université Catholique de Louvain, de Duve Institute, Brussels, Belgium. laurent.bultot@uclouvain.be

FEBS Letters
|December 9, 2008
PubMed

Insights

AMP-activated protein kinase (AMPK) does not directly phosphorylate myosin light chain (MLC). In cells, Rho kinase, not AMPK, mediates MLC phosphorylation during energy depletion, challenging previous assumptions about AMPK signaling pathways.

Area of Science:

  • Molecular Biology
  • Cellular Signaling
  • Biochemistry

Background:

  • Myosin regulatory light chain (MLC) phosphorylation is crucial for cellular functions.
  • AMP-activated protein kinase (AMPK) is a key regulator of cellular energy homeostasis.
  • The direct role of AMPK in MLC phosphorylation has been previously hypothesized.

Purpose of the Study:

  • To investigate the direct phosphorylation kinetics of MLC by recombinant and commercial AMPK.
  • To determine the role of AMPK in MLC phosphorylation in cellular models of energy deprivation.
  • To elucidate the signaling pathways involved in MLC phosphorylation during cellular stress.

Main Methods:

  • In vitro kinase assays comparing recombinant AMPK, commercial rat liver AMPK, and smooth muscle myosin light chain kinase (smMLCK) for MLC phosphorylation.
  • Cellular experiments using Madin-Darby Canine Kidney (MDCK) cells to assess MLC phosphorylation upon AMPK activation.
  • Pharmacological inhibition of Rho kinase to discern its role in AMPK-mediated MLC phosphorylation.

Main Results:

  • Recombinant AMPK exhibited significantly lower MLC phosphorylation rates (over 100-fold less) compared to smMLCK.
  • Commercial rat liver AMPK demonstrated substantial MLC phosphorylation.
  • In MDCK cells, AMPK activation increased MLC phosphorylation, an effect reversed by Rho kinase inhibition without altering AMPK activation.

Conclusions:

  • MLC phosphorylation during energy deprivation is not mediated by direct AMPK action.
  • Rho kinase, rather than AMPK, plays a significant role in regulating MLC phosphorylation in response to cellular energy status.
  • These findings necessitate a re-evaluation of the downstream signaling pathways controlled by AMPK in cellular energy metabolism.

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