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mTORC1 activation regulates beta-cell mass and proliferation by modulation of cyclin D2 synthesis and stability

Norman Balcazar1, Aruna Sathyamurthy, Lynda Elghazi

  • 1Washington University School of Medicine, Division of Endocrinology, Metabolism & Lipid Research, St. Louis, Missouri, 63110, USA.

The Journal of Biological Chemistry
|January 16, 2009
PubMed

Insights

The mechanistic target of rapamycin complex 1 (mTORC1) pathway regulates beta-cell proliferation by controlling cyclin D2 synthesis and stability. This finding suggests rapamycin may hinder islet transplantation success and beta-cell adaptation to insulin resistance.

Area of Science:

  • Cell Biology
  • Endocrinology
  • Metabolism

Background:

  • Growth factors, insulin signaling, and nutrients are key regulators of beta-cell mass and function.
  • The mechanistic target of rapamycin (mTOR) pathway integrates signals from growth factors and nutrients.
  • Understanding how these signals regulate beta-cell mass is crucial.

Purpose of the Study:

  • To investigate the role of mTOR complex 1 (mTORC1) signaling in beta-cell proliferation.
  • To elucidate the mechanisms by which mTORC1 influences beta-cell cycle progression.

Main Methods:

  • Controlled activation of Akt signaling to induce proliferative conditions in beta-cells.
  • Evaluation of mTORC1 signaling and its downstream targets.
  • Analysis of cyclin D2, D3, and Cdk4 activity.

Main Results:

  • mTORC1 signaling is a major regulator of beta-cell cycle progression.
  • mTORC1 modulates the synthesis and stability of cyclin D2, a critical regulator of beta-cell proliferation and mass.
  • mTORC1 activity is linked to cyclin D2, D3, and Cdk4 activity.

Conclusions:

  • mTORC1 signaling directly regulates beta-cell cycle progression through cyclin D2.
  • This provides a mechanism for the antiproliferative effects of rapamycin.
  • Rapamycin use may negatively impact islet transplantation and beta-cell adaptation to insulin resistance.

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