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Development and Application of Rapamycin-regulated Tyrosine Phosphatases
06:56

Development and Application of Rapamycin-regulated Tyrosine Phosphatases

Published on: September 6, 2024

Rheb binds tuberous sclerosis complex 2 (TSC2) and promotes S6 kinase activation in a rapamycin- and

Ariel F Castro1, John F Rebhun, Geoffrey J Clark

  • 1Department of Biochemistry and Molecular Biology, Indiana University School of Medicine and Walther Cancer Institute, Indianapolis, Indiana 46202, USA. acastro@iupui.edu

The Journal of Biological Chemistry
|July 5, 2003
PubMed

Insights

The tuberous sclerosis complex 2 (TSC2) protein regulates protein synthesis by interacting with Rheb-GTP. Rheb activation of S6 kinase, upstream of mTOR, is inhibited by farnesyl transferase inhibitors.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Oncology

Background:

  • The tuberous sclerosis complex 2 (TSC2) gene product is a known negative regulator of protein synthesis.
  • TSC2 shares homology with GTPase-activating proteins for Rap1, suggesting a role for Ras/Rap-related GTPases.

Purpose of the Study:

  • To investigate the involvement of a Ras/Rap-related GTPase in TSC2-mediated regulation of protein synthesis.
  • To determine the interaction between TSC2 and Rheb and its effect on signaling pathways.

Main Methods:

  • In vitro binding assays to assess TSC2 and Rheb-GTP interaction.
  • In vivo experiments to measure Rheb GTP levels.
  • Over-expression studies of Rheb and Rap1 to analyze S6 kinase activation.
  • Treatment with farnesyl transferase inhibitor to evaluate Rheb's effect on S6 phosphorylation.

Main Results:

  • TSC2 was found to bind to Rheb-GTP in vitro.
  • TSC2 reduced Rheb GTP levels in vivo.
  • Over-expression of Rheb, but not Rap1, promoted S6 kinase activation in a rapamycin-dependent manner.
  • Rheb-induced S6 phosphorylation was inhibited by a farnesyl transferase inhibitor.

Conclusions:

  • Rheb acts upstream of mTOR in the regulation of protein synthesis.
  • Rheb is implicated in the Ras-independent anti-neoplastic effects of farnesyl transferase inhibitors.

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