Proc Natl Acad Sci U S A. 1998 Apr 14;95(8):4386-91.

Bcl-XL interacts with Apaf-1 and inhibits Apaf-1-dependent caspase-9 activation.External

Hu, Y., Benedict, M. A., Wu, D., Inohara, N., Nunez, G.,
--- - Departments of Pathology and Comprehensive Cancer Center, 1500 East Medical Center Drive, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
Recent studies indicate that Caenorhabditis elegans CED-4 interacts with and promotes the activation of the death protease CED-3, and that this activation is inhibited by CED-9. Here we show that a mammalian homolog of CED-4, Apaf-1, can associate with several death proteases, including caspase-4, caspase-8, caspase-9, and nematode CED-3 in mammalian cells. The interaction with caspase-9 was mediated by the N-terminal CED-4-like domain of Apaf-1. Expression of Apaf-1 enhanced the killing activity of caspase-9 that required the CED-4-like domain of Apaf-1. Furthermore, Apaf-1 promoted the processing and activation of caspase-9 in vivo. Bcl-XL, an antiapoptotic member of the Bcl-2 family, was shown to physically interact with Apaf-1 and caspase-9 in mammalian cells. The association of Apaf-1 with Bcl-XL was mediated through both its CED-4-like domain and the C-terminal domain containing WD-40 repeats. Expression of Bcl-XL inhibited the association of Apaf-1 with caspase-9 in mammalian cells. Significantly, recombinant Bcl-XL purified from Escherichia coli or insect cells inhibited Apaf-1-dependent processing of caspase-9. Furthermore, Bcl-XL failed to inhibit caspase-9 processing mediated by a constitutively active Apaf-1 mutant, suggesting that Bcl-XL regulates caspase-9 through Apaf-1. These experiments demonstrate that Bcl-XL associates with caspase-9 and Apaf-1, and show that Bcl-XL inhibits the maturation of caspase-9 mediated by Apaf-1, a process that is evolutionarily conserved from nematodes to humans.
PMID: 9539746External
Arrow2 In vitro interaction Arrow2 In vivo interaction Arrow2 Characterization Arrow2 Functional role Arrow2 top
In vivo interaction
  Endogenous
expression
Overexpression DD1 DD2 Reference
Family DD1 DD2 Method Species Region Species Region
CARD Apaf1 Link Caspase4 Co-immunoprecipitation HEK293 Not specified Full length Human Not specified 9539746
CARD Apaf1 Link Caspase9 Co-immunoprecipitation HEK293 Not specified Full length Human Not specified 9539746
CARD Apaf1 Link Caspase9 Co-immunoprecipitation HEK293 Not specified 1-559 Human Not specified 9539746
(Link: click this icon to show interactions only between the two corresponding DDs)
Arrow2 In vitro interaction Arrow2 In vivo interaction Arrow2 Characterization Arrow2 Functional role Arrow2 top
Functional Role
Family DD1 DD2 Method Death-related Death-unrelated Reference
CARD Apaf1 Link Caspase9 β-galactosidase staining Apoptosis (Apoptosome) 9539746
(Link: click this icon to show interactions only between the two corresponding DDs)