Abstract
Bcl-2 and close homologues such as Bcl-xL promote cell survival, while other relatives such as Bax antagonize this function. Since only the pro-survival family members possess a conserved N-terminal region denoted BH4, we have explored the role of this amphipathic helix for their survival function and for interactions with several agonists of apoptosis, including Bax and CED-4, an essential regulator in the nematode Caenorhabditis elegans. BH4 of Bcl-2 could be replaced by that of Bcl-x without perturbing function but not by a somewhat similar region near the N-terminus of Bax. Bcl-2 cell survival activity was reduced by substitutions in two of ten conserved BH4 residues. Deletion of BH4 rendered Bcl-2 (and Bcl-xL) inactive but did not impair either Bcl-2 homodimerization or ability to bind to Bax or five other pro-apoptotic relatives (Bak, Bad, Bik, Bid or Bim). Hence, association with these death agonists is not sufficient to promote cell survival. Significantly, however, Bcl-xL lacking BH4 lost the ability both to bind CED-4 and antagonize its pro-apoptotic activity. These results favour the hypothesis that the BH4 domain of pro-survival Bcl-2 family members allows them to sequester CED-4 relatives and thereby prevent apoptosis.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Apoptosis Regulatory Proteins
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Apoptosis* / drug effects
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Apoptosis* / genetics
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BH3 Interacting Domain Death Agonist Protein
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Bcl-2-Like Protein 11
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Caenorhabditis elegans Proteins*
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Calcium-Binding Proteins / antagonists & inhibitors
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Calcium-Binding Proteins / metabolism*
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Carrier Proteins / metabolism
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Cell Line
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Conserved Sequence*
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Dimerization
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Helminth Proteins / antagonists & inhibitors
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Helminth Proteins / metabolism*
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Humans
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Membrane Proteins / metabolism
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Mitochondrial Proteins
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Molecular Sequence Data
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Protein Binding
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Protein Structure, Tertiary
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Proteins / metabolism
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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-bcl-2 / chemistry*
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Proto-Oncogene Proteins c-bcl-2 / genetics
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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Proto-Oncogene Proteins c-bcl-2 / physiology*
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Sequence Deletion
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Sequence Homology, Amino Acid*
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bcl-2 Homologous Antagonist-Killer Protein
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bcl-2-Associated X Protein
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bcl-Associated Death Protein
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bcl-X Protein
Substances
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Apoptosis Regulatory Proteins
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BAD protein, human
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BAK1 protein, human
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BAX protein, human
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BCL2L1 protein, human
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BCL2L11 protein, human
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BH3 Interacting Domain Death Agonist Protein
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BID protein, human
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BIK protein, human
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Bcl-2-Like Protein 11
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Caenorhabditis elegans Proteins
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Calcium-Binding Proteins
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Carrier Proteins
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Ced-4 protein, C elegans
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Helminth Proteins
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Membrane Proteins
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Mitochondrial Proteins
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Proteins
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-bcl-2
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bcl-2 Homologous Antagonist-Killer Protein
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bcl-2-Associated X Protein
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bcl-Associated Death Protein
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bcl-X Protein