Survival activity of Bcl-2 homologs Bcl-w and A1 only partially correlates with their ability to bind pro-apoptotic family members.
Certain Bcl-2 family members promote cell survival, whereas others promote apoptosis. To explore further how heterodimerization of opposing members affects survival activity, we have compared the abilities of the anti-apoptotic Bcl-w and A1 to bind to the pro-apoptotic Bax, Bak, Bad and Bik and to protect cells from their cytotoxic action. Bcl-w co-immunoprecipitated from cell lysates with Bax, Bak, Bad and Bik, but A1 bound only Bak and Bik. Mutation of A1 at a highly conserved glycine within the BH1 domain prevented binding, but the comparable Bcl-w mutant still bound Bak, Bad and Bik, indicating that the glycine is not essential for all heterodimerization. Bcl-w and A1 protected against apoptosis induced by over-expression of Bax or Bad but not that induced by Bak or Bik. With several gene pairs, binding and protection were discordant. The results may reflect critical threshold affinities but also suggest that certain pro-apoptotic proteins may also contribute to apoptosis by a mechanism independent of binding pro-survival proteins.
Holmgreen
S P
SP
The Walter and Eliza Hall Institute of Medical Research, PO Royal Melbourne Hospital Victoria 3050, Australia.
Huang
D C
DC
Adams
J M
JM
Cory
S
S
D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018398:Homeodomain Proteins; D006801:Humans; D007377:Interleukin-3 / Q000378:metabolism / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D015778:Minor Histocompatibility Antigens; D024101:Mitochondrial Proteins; D017354:Point Mutation; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D051818:Replication Protein C; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein
D051017:Apoptosis Regulatory Proteins; C494819:BAD protein, human; C494772:BAK1 protein, human; C494826:BAX protein, human; C096816:BCL2-related protein A1; C491073:BCL2L2 protein, human; C096820:BIK protein, human; C494820:Bad protein, mouse; C494773:Bak1 protein, mouse; C494827:Bax protein, mouse; C101155:Bcl2l2 protein, mouse; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D007377:Interleukin-3; C096063:MATA1 protein, S cerevisiae; D008565:Membrane Proteins; D015778:Minor Histocompatibility Antigens; D024101:Mitochondrial Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; D051818:Replication Protein C