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. 2006 Dec;8(12):1348-58.
doi: 10.1038/ncb1499. Epub 2006 Nov 19.

Hierarchical regulation of mitochondrion-dependent apoptosis by BCL-2 subfamilies

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Hierarchical regulation of mitochondrion-dependent apoptosis by BCL-2 subfamilies

Hyungjin Kim et al. Nat Cell Biol. 2006 Dec.

Abstract

Although the BCL-2 family constitutes a crucial checkpoint in apoptosis, the intricate interplay between these family members remains elusive. Here, we demonstrate that BIM and PUMA, similar to truncated BID (tBID), directly activate BAX-BAK to release cytochrome c. Conversely, anti-apoptotic BCL-2-BCL-X(L)-MCL-1 sequesters these 'activator' BH3-only molecules into stable complexes, thus preventing the activation of BAX-BAK. Extensive mutagenesis of BAX-BAK indicates that their activity is not kept in check by BCL-2-BCL-X(L)-MCL-1. Anti-apoptotic BCL-2 members are differentially inactivated by the remaining 'inactivator' BH3-only molecules including BAD, NOXA, BMF, BIK/BLK and HRK/DP5. BAD displaces tBID, BIM or PUMA from BCL-2-BCL-X(L) to activate BAX-BAK, whereas NOXA specifically antagonizes MCL-1. Coexpression of BAD and NOXA killed wild-type but not Bax, Bak doubly deficient cells or Puma deficient cells with Bim knockdown, indicating that activator BH3-only molecules function downstream of inactivator BH3-only molecules to activate BAX-BAK. Our data establish a hierarchical regulation of mitochondrion-dependent apoptosis by various BCL-2 subfamilies.

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Comment in

  • Upgrading the BCL-2 network.
    Galonek HL, Hardwick JM. Galonek HL, et al. Nat Cell Biol. 2006 Dec;8(12):1317-9. doi: 10.1038/ncb1206-1317. Nat Cell Biol. 2006. PMID: 17139279 No abstract available.

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