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In Vitro SUMOylation Assay to Study SUMO E3 Ligase Activity
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Regulation of protein tyrosine phosphatase 1B by sumoylation

Shrikrishna Dadke1, Sophie Cotteret, Shu-Chin Yip

  • 1Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA.

Nature Cell Biology
|December 13, 2006
PubMed

Insights

Protein-tyrosine phosphatase 1B (PTP1B) activity is regulated by sumoylation. This process, catalyzed by PIAS1, reduces PTP1B

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Background:

  • Protein-tyrosine phosphatase 1B (PTP1B) negatively regulates growth factor signaling and cell proliferation.
  • The precise regulation of PTP1B activity remains unclear.
  • PTP1B dephosphorylates key receptor tyrosine kinases, including the insulin receptor.

Purpose of the Study:

  • To investigate the regulatory mechanisms of PTP1B activity.
  • To identify proteins that interact with and regulate PTP1B.
  • To elucidate the role of sumoylation in PTP1B function.

Main Methods:

  • Yeast two-hybrid assay to identify interacting proteins.
  • Co-immunoprecipitation in mammalian fibroblasts to confirm protein association.
  • In vitro sumoylation assays to assess catalytic activity.
  • Western blotting to detect sumoylation and protein levels.

Main Results:

  • PIAS1, a SUMO E3 ligase, was identified as a PTP1B-interacting protein.
  • PIAS1 catalyzes the sumoylation of PTP1B in mammalian cells.
  • Sumoylation of PTP1B reduces its catalytic activity and its inhibitory effect on insulin receptor signaling.
  • Insulin-stimulated sumoylation leads to transient downregulation of endogenous PTP1B.

Conclusions:

  • Sumoylation is a novel regulatory mechanism for PTP1B activity.
  • PIAS1-mediated sumoylation modulates PTP1B's role in insulin signaling and cell proliferation.
  • This finding expands the known functions of sumoylation beyond nuclear processes.

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