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Consequences of interrupted Rheb-to-AMPK feedback signaling in tuberous sclerosis complex and cancer

Markus D Lacher1, Roxana J Pincheira, Ariel F Castro

  • 1Helen Diller Family Comprehensive Cancer Center; University of California; San Francisco, CA USA.

Small Gtpases
|December 7, 2011
PubMed

Insights

Rheb activates AMPK and reduces p27 levels, impacting cell growth and tumor formation in Tuberous Sclerosis Complex (TSC). This Rheb-AMPK-p27 signaling may influence TSC disease progression and treatment strategies.

Area of Science:

  • Molecular Biology
  • Cellular Signaling
  • Oncology

Background:

  • Rheb (Ras homolog enriched in brain) GTPase activates mTORC1, promoting cell growth.
  • AMPK (adenosine 5'-monophosphate-activated protein kinase) signals energy shortage, suppressing anabolism and activating TSC1-TSC2 to inhibit Rheb.
  • Tuberous Sclerosis Complex (TSC) involves mutations in TSC1 or TSC2, leading to uncontrolled mTORC1 signaling and cell proliferation.

Purpose of the Study:

  • To investigate an mTORC1-independent Rheb-to-AMPK feedback loop in Tsc2-null TSC models.
  • To explore the role of Rheb-mediated regulation of p27 (p27KIP1) in TSC cell proliferation and tumor formation.
  • To hypothesize the mechanism of Rheb regulating p27 via AMPK activation.

Main Methods:

  • Utilized Tsc2-null in vitro models of Tuberous Sclerosis Complex (TSC).
  • Assessed Rheb signaling, AMPK activation, and p27 nuclear levels.
  • Correlated Rheb-mediated p27 repression with Cdk2 activation, cell proliferation, and tumor formation.

Main Results:

  • Identified an mTORC1-independent feedback loop where Rheb activates AMPK.
  • Rheb activation led to decreased nuclear p27 levels.
  • Rheb-mediated p27 repression correlated with increased Cdk2 activity, cell proliferation, and tumor formation in TSC cells.

Conclusions:

  • Rheb signaling impacts p27 regulation through AMPK activation in TSC.
  • The Rheb-AMPK-p27 axis represents a potential therapeutic target for TSC and related malignancies like S-LAM.
  • Understanding this signaling pathway is crucial for developing novel treatment strategies for TSC.

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