Bak can accelerate chemotherapy-induced cell death independently of its heterodimerization with Bcl-XL and Bcl-2.
Bak has been shown to both promote apoptosis and to inhibit cell death while two other members of the Bcl-2 family of proteins, Bcl-XL and Bcl-2 delay apoptosis induced by various stimuli including chemotherapeutic agents. We generated clones with stable expression of Bak wild-type (wt) and Bak with its BH3 (delta78-86) domain deleted (deltaBH3) in FL5.12 cells or FL5.12 cells expressing either Bcl-XL or Bcl-2 to determine if Bak could accelerate apoptosis and antagonize the death repressor activity of Bcl-XL and Bcl-2 during chemotherapy-induced apoptosis. We found that Bak accelerated cell death in FL5.12 cells treated with etoposide, fluorouracil or taxol. In FL5.12 cells expressing Bcl-XL and Bak wt or Bak deltaBH3, both Bak wt or Bak deltaBH3 were able to antagonize the protective effect of Bcl-XL when treated with etoposide or fluorouracil. Bak wt or Bak deltaBH3 were also able to abrogate the protective effect of Bcl-2 in cells expressing Bcl-2 and Bak wt or Bak deltaBH3 when challenged by etoposide or fluorouracil. Immunoprecipitation studies revealed that deletion of BH3 disrupted heterodimerization between Bak and Bcl-XL and that both Bak wt and Bak deltaBH3 failed to interact with Bcl-2. These results demonstrate that Bak does not require its BH3 domain to promote apoptosis in stably transfected cells. Furthermore, Bak can accelerate chemotherapy-induced cell death independently of its heterodimerization with Bcl-XL and Bcl-2.
Simonian
P L
PL
Department of Pathology and Comprehensive Cancer Center, The University of Michigan Medical School, Ann Arbor 48109, USA.
Grillot
D A
DA
Nuñez
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G
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002460:Cell Line; D019281:Dimerization; D008565:Membrane Proteins / Q000737:chemistry / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry*; D050998:bcl-2 Homologous Antagonist-Killer Protein
D000970:Antineoplastic Agents; D008565:Membrane Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050998:bcl-2 Homologous Antagonist-Killer Protein