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The picky mTORC1 in metabolic enzyme degradation

Yujin Chun1, David A Fruman2, Gina Lee3

  • 1Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine, Irvine, CA, USA.

Molecular Cell
|June 7, 2024
PubMed

Insights

Reduced mTORC1 signaling triggers the breakdown of HMGCS1, a key enzyme in cholesterol synthesis. This process involves the CTLH E3 ligase and the ubiquitin-proteasome system, linking cell growth regulation to metabolic control.

Area of Science:

  • Cellular Biology
  • Biochemistry
  • Metabolism

Background:

  • Mammalian target of rapamycin complex 1 (mTORC1) is a central regulator of cell growth and metabolism.
  • The mevalonate pathway is crucial for cholesterol biosynthesis and cell proliferation.
  • The ubiquitin-proteasome system mediates the degradation of numerous cellular proteins.

Purpose of the Study:

  • To investigate the impact of reduced mTORC1 activity on metabolic enzyme regulation.
  • To identify the specific mechanisms linking mTORC1 signaling to metabolic pathways.
  • To explore the role of protein degradation in mediating mTORC1-dependent metabolic control.

Main Methods:

  • Cellular assays to monitor protein levels and activity.
  • Biochemical analyses of enzyme function and protein interactions.
  • Genetic manipulation to modulate mTORC1 signaling and E3 ligase activity.

Main Results:

  • Reduced mTORC1 activity leads to the degradation of HMGCS1, a rate-limiting enzyme in the mevalonate pathway.
  • This degradation is dependent on the CTLH E3 ligase complex.
  • The ubiquitin-proteasome system is responsible for HMGCS1 turnover.

Conclusions:

  • mTORC1 signaling directly influences the stability of metabolic enzymes.
  • A novel regulatory axis exists between mTORC1, the CTLH E3 ligase, and HMGCS1 degradation.
  • This finding reveals a new mechanism connecting cell growth control with metabolic homeostasis via targeted protein degradation.

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