Membrane translocation and oligomerization of hBok are triggered in response to apoptotic stimuli and Bnip3.
hBok is a human pro-apoptotic member of the Bcl-2 family. By fluorescence in situ hybridization and in silico analysis, hBok was found to be located on chromosome 2q37.3. Its expression was detected in various organs and several hormonally regulated cancer cells. Expression of hBok was shown to be upregulated in estrogen-dependent breast cancer by estrogen deprivation and in myocardial cells during hypoxia. Confocal laser scanning microscopy examinations and subcellular fractionation studies showed that hBok was distributed in both the cytosol and intracellular membranes of healthy cells. Upon overexpression of hBok or stimulation of apoptosis, hBok became integrated into the membrane. Furthermore, apoptosis and oligomerization were promoted by BH3-only proteins, such as Bid, Bnip3 and p53, but prevented by BFL-1. hBok was found to interact with Bnip3. Our findings suggest that functional BH3-only proteins facilite the oligomerization and insertion of hBok into the membrane to activate it.
Gao
S
S
Department of Research and University Women's Hospital, University of Basel, Schanzenstrasse 46, 4031, Basel, Switzerland.
Fu
W
W
Dürrenberger
M
M
De Geyter
C
C
Zhang
H
H
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000502:physiology*; D015687:Cell Hypoxia / Q000502:physiology; D002460:Cell Line; D045744:Cell Line, Tumor; D003600:Cytosol / Q000378:metabolism; D019281:Dimerization; D015870:Gene Expression / Q000235:genetics; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D021381:Protein Transport / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000378:metabolism; D014162:Transfection
C090121:BNIP3 protein, human; C503049:BOK protein, human; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2