Under respiratory growth conditions, Bcl-x(L) and Bcl-2 are unable to overcome yeast cell death triggered by a mutant Bax protein lacking the membrane anchor.
We have reported earlier that cytosolic expression of the full-length human apoptosis inducer Bax-alpha (Bax) in the yeast Saccharomyces cerevisiae suppresses growth and induces mortality in cells containing functional mitochondria. Human Bcl-x(L) overcomes this toxicity. Here we describe that a mutant Bax protein, with a missing membrane anchor region (Bax delta), also inhibits growth and causes cell death in yeast. However, the death inhibitory proteins Bcl-x(L) and Bcl-2 fail to rescue Bax delta-mediated growth inhibition under conditions promoting respiration, although they bind Bax delta in the cell. Results in Jurkat T-cells corroborate that Bcl-x(L) is much less efficient at rescuing mammalian cells from the effect of Bax delta than from full length Bax. We have also inquired if the respiration-dependent toxicity of Bax and Bax delta in yeast is nullified by Bcl-x(L)delta and Bcl-2delta, molecules which lack membrane anchors but bind Bax in the yeast two-hybrid system. It appears that, under conditions which facilitate respiration in yeast, Bcl-x(L)delta and Bcl-2delta are incapable of rescuing both Bax-containing and Bax delta-containing cells. Our results open up the interesting possibility that there might exist proteins, unrelated to the Bcl-2 family, which could negate death induced by a membrane anchor-free form of Bax.
Clow
A
A
Oncology Research, Novartis Pharma AG, Basel, Switzerland.
Greenhalf
W
W
Chaudhuri
B
B
D000595:Amino Acid Sequence; D017209:Apoptosis; D001483:Base Sequence; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism; D017931:DNA Primers; D006801:Humans; D019169:Jurkat Cells; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D011233:Precipitin Tests; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
C494826:BAX protein, human; C494811:BCL2L1 protein, human; D017931:DNA Primers; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D010100:Oxygen