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14-3-3beta binds to and negatively regulates the tuberous sclerosis complex 2 (TSC2) tumor suppressor gene product,

Stuart D Shumway1, Yong Li, Yue Xiong

  • 1Lineberger Comprehensive Cancer Center, Department of Biochemistry and Biophysics, Program in Molecular Biology and Biotechnology, University of North Carolina at Chapel Hill, 27599-7295, USA.

The Journal of Biological Chemistry
|December 7, 2002
PubMed

Insights

The tuberous sclerosis complex (TSC) proteins TSC1 and TSC2 regulate cell growth. A novel interaction with 14-3-3beta protein negatively impacts TSC protein function, affecting cellular growth regulation.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Oncology

Background:

  • The tuberous sclerosis complex (TSC) proteins, TSC1 (hamartin) and TSC2 (tuberin), are crucial negative regulators of cellular growth.
  • They function downstream of the phosphatidylinositol 3-kinase-Akt signaling pathway, inhibiting the ribosomal S6 kinase (S6K) pathway.

Purpose of the Study:

  • To investigate novel interactions with the TSC1-TSC2 complex.
  • To elucidate the functional consequences of these interactions on TSC protein activity.

Main Methods:

  • Co-immunoprecipitation assays to identify protein interactions.
  • Western blotting to assess protein phosphorylation levels (e.g., S6K).
  • Site-directed mutagenesis to study the role of specific phosphorylation sites.

Main Results:

  • A novel interaction between TSC2 and 14-3-3beta was identified.
  • 14-3-3beta forms a ternary complex with TSC1 and TSC2 without disrupting TSC1-TSC2 binding.
  • This interaction requires TSC2 phosphorylation at a novel site, distinct from known Akt phosphorylation sites.
  • Overexpression of 14-3-3beta impairs the TSC1-TSC2 complex's ability to inhibit S6K phosphorylation.
  • The inhibitory effect of 14-3-3beta is dependent on its direct interaction with TSC2.

Conclusions:

  • 14-3-3beta negatively regulates the function of the TSC1-TSC2 complex.
  • This regulation occurs through a direct interaction with TSC2, impacting its ability to control S6K phosphorylation and cellular growth.
  • These findings reveal a new layer of regulation for the TSC pathway, with implications for tuberous sclerosis complex pathogenesis.

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