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ERK regulation upon contact inhibition in fibroblasts

Joshua Wayne1, Jennifer Sielski, Ahmed Rizvi

  • 1Department of Biology, Monmouth University, West Long Branch, NJ 07764, USA.

Molecular and Cellular Biochemistry
|February 10, 2006
PubMed

Insights

Contact inhibition of normal fibroblasts involves decreased extracellular signal-regulated kinase (ERK) activity, linked to increased mitogen-activated protein kinase phosphatases (MKPs). This regulation may involve altered cellular redox environments.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • Mitogen-activated protein (MAP) kinase activation is crucial for cell growth stimulation.
  • The regulation of MAP kinase pathways during contact-inhibited growth control remains poorly understood.
  • Extracellular signal-regulated kinase (ERK) is a key MAP kinase involved in cell proliferation.

Purpose of the Study:

  • To investigate the role of ERK regulation during the transition to a contact-inhibited state in normal fibroblasts.
  • To compare ERK pathway regulation in contact-inhibited fibroblasts versus non-contact-inhibited fibrosarcoma cells.
  • To explore the potential influence of the cellular redox environment on ERK inactivation.

Main Methods:

  • Normal fibroblasts (BJ) and fibrosarcoma cells (HT-1080) were cultured to varying confluency levels.
  • Western blot analysis was used to assess MAP kinase phosphatase (MKP) expression.
  • Levels of active ERK and MAP ERK kinase (MEK) were quantified.

Main Results:

  • In normal fibroblasts, active MEK and ERK levels decreased upon reaching contact inhibition.
  • Concurrently, protein levels of MKP-1, MKP-2, and MKP-3 increased in contact-inhibited fibroblasts.
  • Fibrosarcoma cells exhibited a lack of density-dependent regulation of the ERK pathway; altering their redox state increased MKP-1 expression.

Conclusions:

  • Contact inhibition in normal fibroblasts is associated with the inactivation of the ERK pathway.
  • Increased expression of MKPs (MKP-1, MKP-2, MKP-3) plays a role in ERK inactivation during contact inhibition.
  • The altered cellular redox environment during contact inhibition may contribute to ERK regulation by MKPs.

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