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Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development
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Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development

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The mixed-lineage kinase DLK undergoes Src-dependent tyrosine phosphorylation and activation in cells exposed to

Alex Daviau1, Marco Di Fruscio, Richard Blouin

  • 1Département de biologie, Faculté des sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1.

Cellular Signalling
|January 17, 2009
PubMed

Insights

Mixed-lineage kinases (MLKs) like DLK are activated by tyrosine phosphorylation, a process dependent on Src family kinases. This phosphorylation is crucial for DLK

Area of Science:

  • Cellular signaling pathways
  • Protein kinase regulation
  • Molecular biology

Background:

  • Mixed-lineage kinases (MLKs) are a subgroup of MAP kinase kinase kinases (MAPKKKs).
  • Serine/threonine phosphorylation is suggested to be required for MLK activation in existing literature.
  • The specific role of tyrosine phosphorylation in MLK activation remains less understood.

Purpose of the Study:

  • To investigate the role of tyrosine phosphorylation in the activation of the mixed-lineage kinase DLK.
  • To elucidate the involvement of Src family kinases in DLK activation.
  • To determine DLK's function in platelet-derived growth factor (PDGF) signaling.

Main Methods:

  • Utilizing vanadate, a protein tyrosine phosphatase inhibitor, to induce tyrosine phosphorylation.
  • Employing Src family kinase inhibitors (e.g., PP2) and short hairpin RNA (shRNA) to assess kinase dependency.
  • Performing experiments with knockout fibroblasts lacking Src, Yes, and Fyn, followed by reintroduction of kinases.
  • Using RNA interference to deplete DLK and examining downstream signaling pathways (ERK, Akt).

Main Results:

  • DLK activation by vanadate is accompanied by tyrosine phosphorylation, which is essential for its enzymatic activity.
  • Vanadate-induced DLK activation and tyrosine phosphorylation are blocked by Src inhibition or depletion.
  • DLK activation is impaired in cells lacking Src family kinases, but restored upon reintroduction of Src or Fyn.
  • PDGF stimulation also induces DLK tyrosine phosphorylation and activation via a Src-dependent mechanism.
  • DLK depletion significantly reduces PDGF-stimulated ERK and Akt activation.

Conclusions:

  • Src-dependent tyrosine phosphorylation is a key regulatory mechanism for DLK activity.
  • DLK plays a significant role in mediating platelet-derived growth factor (PDGF) signaling pathways.
  • These findings reveal a novel mechanism for MLK activation and signaling pathway involvement.

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