Neuron-specific Bcl-2 Homology 3 Domain-only Splice Variant of Bak Is Anti-apoptotic in Neurons, but Pro-apoptotic in Non-neuronal Cells

• Published in: The Journal of biological chemistry 2001-05, Vol.276 (19), p.16240-16247
• Main Authors: Sun, Yun-Fu, Yu, Li-Ying, Saarma, Mart, Timmusk, Tõnis, Arumäe, Urmas
• Format: Article
• Language: English
• Subjects: Alternative Splicing; Amino Acid Sequence; Animals; Apoptosis - physiology; Base Sequence; bcl-2 Homologous Antagonist-Killer Protein; Brain - cytology; Brain - physiology; Cells, Cultured; Chlorocebus aethiops; COS Cells; Genetic Variation; HeLa Cells; Humans; Membrane Proteins - chemistry; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mice; Molecular Sequence Data; Neurons - cytology; Neurons - physiology; Organ Specificity; Protein Isoforms - chemistry; Protein Isoforms - genetics; Protein Isoforms - metabolism; Proto-Oncogene Proteins c-bcl-2 - chemistry; Proto-Oncogene Proteins c-bcl-2 - genetics; Proto-Oncogene Proteins c-bcl-2 - metabolism; Recombinant Proteins - metabolism; Sequence Alignment; Sequence Homology, Amino Acid; src Homology Domains; Superior Cervical Ganglion - cytology; Superior Cervical Ganglion - physiology; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M010419200

We have identified and characterized N-Bak, a neuron-specific isoform of the pro-apoptotic Bcl-2 family member Bak. N-Bak is generated by neuron-specific splicing of a novel 20-base pair exon, which changes the previously described Bak, containing Bcl-2 homology (BH) domains BH1, BH2, and BH3, into a shorter BH3-only protein. As demonstrated by reverse transcription-polymerase chain reaction and RNase protection assay, N-Bak transcripts are expressed only in central and peripheral neurons, but not in other cells, whereas the previously described Bak is expressed ubiquitously, but not in neurons. Neonatal sympathetic neurons microinjected with N-Bak resisted apoptotic death caused by nerve growth factor (NGF) removal, whereas microinjectedBak accelerated NGF deprivation-induced death. Overexpressed Bak killed sympathetic neurons in the presence of NGF, whereas N-Bak did not. N-Bak was, however, still death-promoting when overexpressed in non-neuronal cells. Thus, N-Bak is an anti-apoptotic BH3-only protein, but only in the appropriate cellular environment. This is the first example of a neuron-specific Bcl-2 family member.