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Pro‐death Bax Has an Intrinsic Capability to Induce Aggregate‐dependent Caspase 8‐mediated Cell Death
Author(s) -
Manas Adriana,
Wang Sheng,
Li Jiajun,
Nelson Adam,
Davis Aislinn,
Lamerand Sydney,
Zhang Huaiyuan,
Xiang Jialing
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.774.9
Subject(s) - programmed cell death , exon , caspase , bcl 2 associated x protein , alternative splicing , gene isoform , microbiology and biotechnology , apoptosis , biology , caspase 8 , chemistry , caspase 3 , biochemistry , gene
BaxΔ2 is a unique functional Bax isoform resulted from the combination of a mononucleotide deletion and an alternative splicing in the N‐terminus. The rest of the sequence is the same between Baxα and BaxΔ2. However, BaxΔ2 is unable to target mitochondria due to the loss of helix α1, encoded by exon 2. Instead, it forms cytosolic aggregates to activate caspase 8‐dependent death pathway. The functional domains involved in BaxΔ2 aggregation and cytotoxicity remained elusive. Using computational modeling in combination with biochemical and cellular analysis, we show here that the drastic changes in the BaxΔ2 N‐terminus have no significant impact on either aggregation or caspase 8 activation. In addition, the hallmark BH3‐killing domain is necessary but not sufficient for either aggregation or cell death. The intact core region of BaxΔ2 encoded by exons 3, 4, and 5 is required for the formation of large aggregates, which are essential for BaxΔ2 cytotoxicity. Surprisingly, aggregation by itself is still not sufficient to trigger cell death. The C‐terminal end encoded by exon 6 is essential for activation of caspase 8. Finally, the C‐terminal conformation, but not the primary sequence, appears to be responsible for the aggregate‐mediated caspase 8 activation and cell death. As Baxα with deletion of exon 2 behaves the same as BaxΔ2, and also shares the same C‐terminus sequence or conformational motifs with most Bax‐isoform family members, these results imply that Bax isoforms may have an intrinsic ability to activate caspase 8 if they fail to target mitochondria. Support or Funding Information This work is supported by NIH R15CA195526 grant