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Perturbation of the Bcl-2 network and an induced Noxa/Bcl-xL interaction trigger mitochondrial dysfunction after DNA

Hernando Lopez1, Liqiang Zhang1, Nicholas M George1

  • 1Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-7696.

The Journal of Biological Chemistry
|March 13, 2010
PubMed

Insights

DNA damage triggers apoptosis by disrupting the Bcl-2 network. Loss of Mcl-1 and induced Noxa/Bcl-xL interaction initiate mitochondrial dysfunction, leading to cell death.

Area of Science:

  • Cellular Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The precise mechanisms by which apoptotic stimuli induce mitochondrial dysfunction are not fully understood.
  • The Bcl-2 protein family plays a critical role in regulating apoptosis, particularly through interactions with mitochondria.

Purpose of the Study:

  • To investigate the involvement of the Bcl-2 network in DNA damage-induced apoptosis.
  • To identify key protein interactions that trigger mitochondrial dysfunction following DNA damage.

Main Methods:

  • Screening of the entire Bcl-2 network in HeLa cells treated with DNA damaging agents (camptothecin, UV).
  • Utilizing a His-tagged Bcl-xL expression system to capture interacting BH3-only proteins.
  • Comparative analysis of protein interactions in response to DNA damage versus death receptor engagement in HeLa and A431 cells.

Main Results:

  • Apoptosis required the elimination of both anti-apoptotic Bcl-xL and Mcl-1.
  • Pro-apoptotic proteins Bak, Bad, Bim, and Noxa were essential for DNA damage-induced apoptosis.
  • Noxa exhibited induced binding to Bcl-xL after DNA damage, but not death receptor engagement, becoming "Mcl-1-free".
  • This Noxa/Bcl-xL interaction triggered cytochrome c release and apoptosis, and was inhibited by Mcl-1.

Conclusions:

  • Loss or inactivation of Mcl-1 is crucial for initiating apoptosis after DNA damage.
  • An induced interaction between Noxa and Bcl-xL, following Mcl-1 loss, acts as a key trigger for mitochondrial dysfunction in DNA damage-induced apoptosis.

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