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Published on: September 28, 2012

Damaged microtubules can inactivate BCL-2 by means of the mTOR kinase

A Calastretti1, A Bevilacqua, C Ceriani

  • 1Department of Pharmacology, University of Milan, Via Vanvitelli 32, Milan 20129, Italy.

Oncogene
|October 11, 2001
PubMed

Insights

Rapamycin inhibits mTOR kinase, impacting cell growth and apoptosis by increasing p27(kip1) and BCL-2 levels. It also blocks taxol-induced apoptosis, revealing mTOR

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • The serine/threonine mTOR kinase regulates cell growth and survival.
  • Apoptosis, or programmed cell death, is a critical process in multicellular organisms.
  • BCL-2 protein is a key regulator of apoptosis, often overexpressed in cancers.

Purpose of the Study:

  • To investigate the role of mTOR kinase in regulating cell growth and apoptosis in human B-cell lines.
  • To elucidate the mechanism by which rapamycin affects p27(kip1) and BCL-2 protein levels.
  • To explore the interaction between mTOR signaling and microtubule-targeting agents like taxol in apoptosis.

Main Methods:

  • Treatment of human B-cell lines with rapamycin and/or taxol.
  • Cell cycle analysis using flow cytometry.
  • Western blot analysis to quantify protein levels (p27(kip1), BCL-2) and phosphorylation status.
  • Assessment of apoptosis and hyperdiploidy.

Main Results:

  • Rapamycin inhibited cell growth and induced G(1) arrest by increasing p27(kip1).
  • Rapamycin significantly increased BCL-2 protein levels by inhibiting its phosphorylation, independent of mRNA levels.
  • Rapamycin counteracted taxol-induced apoptosis and BCL-2 phosphorylation, indicating mTOR's role in the apoptotic cascade initiated by microtubule damage.

Conclusions:

  • mTOR kinase plays a crucial role in regulating both cell proliferation and apoptosis.
  • Rapamycin's inhibition of mTOR affects key cell cycle and apoptosis regulators, including p27(kip1) and BCL-2.
  • mTOR is part of an enzymatic pathway that links microtubule integrity to BCL-2 phosphorylation and apoptosis, highlighting its nodal function in cell signaling.

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