Truncated forms of BNIP3 act as dominant negatives inhibiting hypoxia-induced cell death.
BNIP3 (Bcl-2/adenovirus E1B Nineteen Kilodalton Interacting Protein) is a pro-cell death member of the Bcl-2 family of proteins. Its expression is induced by the transcription factor Hypoxia Inducible Factor-1 (HIF-1) under conditions of low oxygen (hypoxia) and is found over expressed in hypoxic regions of many tumors. When over expressed, BNIP3 induces cell death through induction of mitochondrial dysfunction that is dependent on the presence of BNIP3's TM domain. Herein, we have determined that the SkOv3 ovarian cancer cell line expresses a truncated BNIP3 protein, which results in the elimination of the transmembrane domain. Truncation that eliminates all four domains of BNIP3 protein also inhibits hypoxia-induced cell death in SkOv3, HEK293, U251 and MCF-7 cells. Three different mutations in a BNIP3 expression vector that lead to a truncated BNIP3 protein, lacking TM domain only, or lacking CD, BH3, and TM domains resulted in inhibition of hypoxia-induced cell death when transfected into HEK293 cells. We found that truncated BNIP3 failed to associate with the mitochondria and the truncated BNIP3 lacking all four domains can bind to wild type BNIP3. Taken together, truncation of BNIP3 could be a novel mechanism for cancer cells to avoid hypoxia-induced cell death mediated by BNIP3 over expression.
Manitoba Institute of Cell Biology, Winnipeg, Manitoba, Canada.
Nicolle
N
Bristow
Teralee R
TR
Burton
Elizabeth S
ES
Henson
Coleen
C
Ong-Justiniano
Michelle
M
Brown
Spencer B
SB
Gibson
D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D049109:Cell Proliferation; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D005799:Genes, Dominant; D006801:Humans; D000860:Hypoxia / Q000378:metabolism / Q000517:prevention & control*; D007124:Immunoenzyme Techniques; D008565:Membrane Proteins / Q000737:chemistry / Q000502:physiology*; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured
C090121:BNIP3 protein, human; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins