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PtdIns(3,4,5)P3-Dependent Activation of the mTORC2 Kinase Complex

Pengda Liu1, Wenjian Gan1, Y Rebecca Chin1

  • 1Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.

Cancer Discovery
|August 22, 2015
PubMed
Abstract

Insights

Researchers discovered how the SIN1-PH domain regulates mTORC2 activity. Phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3) binding to SIN1-PH releases mTOR inhibition, activating mTORC2 and impacting cell growth and tumor formation.

Area of Science:

  • Cellular Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The mechanistic target of rapamycin (mTOR) pathway is crucial for cell growth and metabolism, with mTORC1 and mTORC2 complexes playing distinct roles.
  • While mTORC1 regulation is well-understood, the upstream mechanisms controlling mTORC2 activation remain largely unknown.

Purpose of the Study:

  • To elucidate the regulatory mechanism of mTORC2 activation.
  • To identify the role of the SIN1-PH domain in mTORC2 regulation and its implications in cancer.

Main Methods:

  • Investigated the interaction between the SIN1 pleckstrin homology (PH) domain and the mTOR kinase domain.
  • Utilized lipid-binding assays to determine the role of phosphatidylinositol phosphates (PIPs) in SIN1-PH function.
  • Analyzed patient-derived mutations in the SIN1-PH domain to assess their impact on mTORC2 activity.

Main Results:

  • The SIN1-PH domain directly interacts with the mTOR kinase domain, suppressing mTORC2 activity.
  • Phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3) specifically binds to SIN1-PH, releasing its inhibitory effect and activating mTORC2.
  • Mutations in SIN1-PH that disrupt PtdIns(3,4,5)P3 binding inactivate mTORC2, while cancer-associated mutations enhance mTORC2 activity, promoting tumorigenesis.

Conclusions:

  • Uncovered a PI3K-dependent mechanism for mTORC2 activation mediated by PtdIns(3,4,5)P3 binding to SIN1-PH.
  • Demonstrated that SIN1-PH mutations can lead to oncogenic activation of mTORC2, contributing to tumor formation.

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