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The Fbw7 tumor suppressor regulates glycogen synthase kinase 3 phosphorylation-dependent c-Myc protein degradation

Markus Welcker1, Amir Orian, Jianping Jin

  • 1Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.

Proceedings of the National Academy of Sciences of the United States of America
|May 20, 2004
PubMed

Insights

The Fbw7 tumor suppressor targets the Myc oncoprotein for degradation. Loss of Fbw7 function leads to Myc accumulation and promotes cancer development.

Area of Science:

  • Oncology
  • Molecular Biology
  • Biochemistry

Background:

  • Myc proteins are crucial regulators of cell growth and division.
  • Dysregulation of Myc is frequently observed in various human cancers.
  • Fbw7 acts as a tumor suppressor by regulating the stability of key oncoproteins.

Purpose of the Study:

  • To investigate the role of Fbw7 in the regulation of c-Myc.
  • To elucidate the mechanism by which Fbw7 controls c-Myc stability.
  • To understand the implications of Fbw7 loss in cancer pathogenesis.

Main Methods:

  • In vivo and in vitro assays to study c-Myc turnover and ubiquitination.
  • Phosphorylation analysis of c-Myc at threonine-58 (T58).
  • Assessment of Fbw7 binding to c-Myc.

Main Results:

  • Fbw7 promotes proteasome-dependent degradation and ubiquitination of c-Myc.
  • Phosphorylation of c-Myc at T58 by glycogen synthase kinase 3 is critical for Fbw7 binding and degradation.
  • Mutations at T58 in c-myc are common in lymphoma, suggesting a link between Fbw7 loss and c-Myc activation in cancer.

Conclusions:

  • Fbw7-mediated degradation of c-Myc is a critical tumor-suppressive mechanism.
  • Impaired Fbw7 function leads to c-Myc accumulation and contributes to oncogenesis.
  • Fbw7's role in degrading multiple oncoproteins highlights its importance in preventing uncontrolled cell proliferation during tumorigenesis.

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