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Bcl-2 Phosphorylation by p38 MAPK: identification of target sites and biologic consequences

Giovanna De Chiara1, Maria Elena Marcocci2, Maria Torcia3

  • 1Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena 299, I-00161 Rome, Italy.

The Journal of Biological Chemistry
|May 23, 2006
PubMed

Insights

Phosphorylation of BCL2 protein by p38 MAPK at Ser87 and Thr56 residues reduces its antiapoptotic function. This critical event in early apoptosis induction is observed during cellular stress, like serum deprivation.

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Biochemistry

Background:

  • The antiapoptotic protein BCL2's function is regulated by phosphorylation.
  • p38 Mitogen-Activated Protein Kinase (MAPK) interacts with BCL2 at the mitochondria.
  • The BH3 and BH4 domains of BCL2 are linked by a loop susceptible to phosphorylation.

Purpose of the Study:

  • To identify specific BCL2 residues phosphorylated by p38 MAPK.
  • To determine the functional consequence of this phosphorylation on BCL2's antiapoptotic activity.
  • To investigate the role of p38 MAPK-mediated BCL2 phosphorylation in early apoptosis during cellular stress.

Main Methods:

  • Mass spectrometry techniques were employed to identify phosphorylated residues.
  • Specific anti-phosphopeptide antibodies were used to detect phosphorylated BCL2.
  • Experiments utilized p38alpha knock-out (p38alpha(-/-)) and wild-type (p38alpha(+/+)) embryonic fibroblasts (MEF).

Main Results:

  • Serine 87 (Ser87) and Threonine 56 (Thr56) were identified as the BCL2 residues phosphorylated by p38 MAPK.
  • Phosphorylation of Ser87 and Thr56 leads to a decrease in BCL2's antiapoptotic potential.
  • p38 MAPK-induced BCL2 phosphorylation is crucial for early apoptosis following serum deprivation in MEFs, evidenced by cytochrome c release and caspase activation.

Conclusions:

  • p38 MAPK directly phosphorylates BCL2 at Ser87 and Thr56, diminishing its antiapoptotic role.
  • This phosphorylation event is a key mechanism in the early stages of apoptosis induced by cellular stress.
  • The findings highlight a novel regulatory pathway for apoptosis involving direct kinase-substrate interaction at the mitochondria.

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