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Regulation of protein tyrosine phosphatase 1B in intact cells by S-nitrosothiols

Sheng Li1, A Richard Whorton

  • 1Department of Pharmacology and Cancer Biology, C138B LSRC, Box 3813, Duke University Medical Center, Durham, NC 27710-0001, USA.

Archives of Biochemistry and Biophysics
|February 8, 2003
PubMed

Insights

Nitric oxide (NO) reversibly inhibits Protein Tyrosine Phosphatase 1B (PTP1B) by modifying its active site cysteine. This inhibition enhances EGF receptor phosphorylation, impacting cellular signaling pathways.

Area of Science:

  • Biochemistry
  • Cellular Signaling
  • Molecular Biology

Background:

  • Protein tyrosine phosphatases (PTPases) regulate cellular signaling by dephosphorylating phosphoproteins.
  • Oxidation of the active site cysteine in PTPases leads to loss of activity and accumulation of phosphoproteins.
  • Epidermal Growth Factor (EGF) stimulation can inhibit PTP1B, enhancing EGF receptor phosphorylation.

Purpose of the Study:

  • To investigate the effect of nitric oxide (NO) on Protein Tyrosine Phosphatase 1B (PTP1B) activity.
  • To determine the mechanism and reversibility of NO-induced PTP1B inhibition.
  • To assess the impact of PTP1B inhibition on EGF receptor phosphorylation.

Main Methods:

  • Exposure of A431 and Jurkat cells to NO donors.
  • Measurement of PTP1B activity.
  • Use of 3-maleimidylpropionylbiocytin (MPB) to assess thiol redox status.
  • Immunoprecipitation of PTP1B to analyze thiol modification.
  • Reversibility studies using DTT and ascorbate.

Main Results:

  • Nitrosothiols rapidly inhibited PTP1B activity, an effect enhanced by cysteine.
  • Thiol modification of PTP1B correlated with loss of activity.
  • Inhibition and modification were reversible in cells and cell lysates with DTT.
  • Evidence suggested mixed disulfide formation (e.g., glutathionylation) rather than S-nitrosylation as the inhibitory mechanism.
  • PTP1B inhibition by nitrosothiols led to EGF receptor phosphorylation without added EGF.

Conclusions:

  • NO reversibly inhibits PTP1B, likely through mixed disulfide formation.
  • PTP1B inhibition by NO can enhance EGF receptor phosphorylation, modulating signaling pathways.
  • NO plays a significant role in regulating phosphoprotein activity through PTPase inhibition.

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