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Non-regulated and stimulated mechanisms cooperate in the nuclear accumulation of MEK1

Z Yao1, I Flash, Z Raviv

  • 1Department of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel.

Oncogene
|December 26, 2001
PubMed

Insights

Mitogen-activated protein kinase kinases (MEKs) use both constant and stimulated pathways for nuclear translocation. This dual mechanism allows for MEK regulation in both resting and stimulated cells.

Area of Science:

  • Cellular biology
  • Molecular signaling
  • Signal transduction pathways

Background:

  • Mitogen-activated protein kinase kinases (MEKs) are key components of the ERK cascade.
  • MEKs exhibit dynamic nuclear-cytosolic shuttling, with proposed distinct translocation mechanisms.
  • Understanding MEK nuclear import/export is crucial for comprehending cellular responses to stimuli.

Purpose of the Study:

  • To investigate the coexistence of different nuclear translocation mechanisms for MEKs.
  • To elucidate the roles of regulated and unregulated processes in MEK nuclear import.
  • To determine the impact of mitogenic stimulation on MEK nuclear localization.

Main Methods:

  • Utilized leptomycin B (LMB), a nuclear export inhibitor, to induce nuclear accumulation of MEKs.
  • Stimulated cells with Epidermal Growth Factor (EGF), TPA, and peroxovanadate in the presence of LMB.
  • Assessed the effect of MEK inhibitors and inactive MEK1 forms on EGF-stimulated translocation.
  • Monitored ERK cascade activation and MEK nuclear accumulation.

Main Results:

  • Leptomycin B (LMB) treatment induced significant nuclear accumulation of MEKs.
  • Mitogenic stimulation (EGF, TPA, peroxovanadate) further enhanced LMB-induced MEK nuclear translocation.
  • EGF-stimulated translocation was sensitive to MEK inhibitors and inactive MEK1, unlike LMB-induced translocation.
  • LMB alone caused minor ERK cascade activation, partially contributing to MEK nuclear accumulation.

Conclusions:

  • MEKs utilize a combination of non-regulated and stimulated mechanisms for nuclear translocation.
  • These dual pathways contribute to MEK nuclear presence in both resting and mitogenically stimulated cells.
  • The findings reveal a complex regulatory system governing MEK nuclear localization within the ERK pathway.

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