NH2-terminal BH4 Domain of Bcl-2 Is Functional for Heterodimerization with Bax and Inhibition of Apoptosis

The Bcl-2 family proteins comprise pro-apoptotic as well as anti-apoptotic members. Heterodimerization between members of the Bcl-2 family proteins is a key event in the regulation of apoptosis. We report here that Bcl-2 protein was selectively cleaved by active caspase-3-like proteases in CTLL-2 ce...

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Bibliographic Details
Published in:The Journal of biological chemistry 1999-07, Vol.274 (29), p.20415-20420
Main Authors: Hirotani, M, Zhang, Y, Fujita, N, Naito, M, Tsuruo, T
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Apoptosis
bcl-2-Associated X Protein
Caspases - metabolism
Cell Line
Dimerization
Enzyme Activation
Humans
Hydrolysis
Mice
Molecular Sequence Data
Mutagenesis, Site-Directed
Protein Binding
Proto-Oncogene Proteins - metabolism
Proto-Oncogene Proteins c-bcl-2 - chemistry
Proto-Oncogene Proteins c-bcl-2 - genetics
Proto-Oncogene Proteins c-bcl-2 - metabolism
Sequence Homology, Amino Acid
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Summary:The Bcl-2 family proteins comprise pro-apoptotic as well as anti-apoptotic members. Heterodimerization between members of the Bcl-2 family proteins is a key event in the regulation of apoptosis. We report here that Bcl-2 protein was selectively cleaved by active caspase-3-like proteases in CTLL-2 cell apoptosis in response to interleukin-2 deprivation. Structural and functional analyses of the cleaved fragment revealed that the NH 2 -terminal region of Bcl-2 (1–34 amid acids) was required for its anti-apoptotic activity and heterodimerization with pro-apoptotic Bax protein. Site-directed mutagenesis of the NH 2 -terminal region showed that substitutions of hydrophobic residues of BH4 domain resulted in the loss of ability to form a heterodimer with Bax. Particularly instructive was that the V15E mutant of Bcl-2, which completely lost the ability to form a heterodimer with Bax, failed to inhibit Bax- and staurosporine-induced apoptosis. Our results suggest that the BH4 domain of Bcl-2 is critical for its heterodimerization with Bax and for exhibiting anti-apoptotic activity. Therefore, agents interferring with the critical residues of the BH4 domain may provide a new strategy in cancer therapy by impairing Bcl-2 function.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.274.29.20415