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BCL-2 is phosphorylated and inactivated by an ASK1/Jun N-terminal protein kinase pathway normally activated at G(2)/M

K Yamamoto1, H Ichijo, S J Korsmeyer

  • 1Departments of Pathology and Medicine, Harvard Medical School and Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA.

Molecular and Cellular Biology
|November 24, 1999
PubMed

Insights

Stress response kinases phosphorylate BCL-2 during the G(2)/M cell cycle phase, inactivating its anti-apoptotic function. This phosphorylation makes cells more susceptible to death signals, impacting cell fate decisions.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Signal transduction pathways regulate BCL-2 family proteins, influencing apoptosis susceptibility.
  • Microtubule-damaging agents induce cell cycle arrest at G(2)/M and can modify BCL-2.
  • Understanding BCL-2 regulation is crucial for controlling cell death.

Purpose of the Study:

  • To identify specific residues on BCL-2 phosphorylated by microtubule-damaging agents.
  • To determine the functional consequence of BCL-2 phosphorylation on apoptosis.
  • To elucidate the cell cycle phase and signaling pathway involved in BCL-2 phosphorylation.

Main Methods:

  • Two-dimensional peptide mapping and sequencing to identify phosphorylation sites.
  • Site-directed mutagenesis (e.g., Ser70Ala) to assess functional impact.
  • Cell cycle synchronization (elutriation) and analysis of BCL-2 phosphorylation.
  • Kinase activity assays and dominant-negative kinase expression studies.

Main Results:

  • Identified Ser70, Ser87, and Thr69 as key phosphorylation sites on BCL-2.
  • Phosphorylation of these sites inactivates BCL-2's anti-apoptotic function, increasing susceptibility to death signals.
  • BCL-2 is phosphorylated specifically during the G(2)/M phase of the cell cycle.
  • The ASK1/JNK1 pathway was identified as responsible for phosphorylating BCL-2 in vivo.
  • Inhibition of ASK1, MKK7, and JNK1 blocked paclitaxel-induced BCL-2 phosphorylation.

Conclusions:

  • Stress-induced BCL-2 phosphorylation at G(2)/M serves as a physiologic mechanism to inactivate its anti-apoptotic role.
  • This inactivation increases cellular vulnerability to death signals during a critical phase of the cell cycle.
  • The ASK1/JNK1 pathway is a key regulator of BCL-2 phosphorylation in response to cellular stress and cell cycle progression.

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