Structural highlights
Function
[APAF_HUMAN] Oligomeric Apaf-1 mediates the cytochrome c-dependent autocatalytic activation of pro-caspase-9 (Apaf-3), leading to the activation of caspase-3 and apoptosis. This activation requires ATP. Isoform 6 is less effective in inducing apoptosis.[1] [2] [CYC_HORSE] Electron carrier protein. The oxidized form of the cytochrome c heme group can accept an electron from the heme group of the cytochrome c1 subunit of cytochrome reductase. Cytochrome c then transfers this electron to the cytochrome oxidase complex, the final protein carrier in the mitochondrial electron-transport chain. Plays a role in apoptosis. Suppression of the anti-apoptotic members or activation of the pro-apoptotic members of the Bcl-2 family leads to altered mitochondrial membrane permeability resulting in release of cytochrome c into the cytosol. Binding of cytochrome c to Apaf-1 triggers the activation of caspase-9, which then accelerates apoptosis by activating other caspases (By similarity).
Publication Abstract from PubMed
Mammalian intrinsic apoptosis requires activation of the initiator caspase-9, which then cleaves and activates the effector caspases to execute cell killing. The heptameric Apaf-1 apoptosome is indispensable for caspase-9 activation by together forming a holoenzyme. The molecular mechanism of caspase-9 activation remains largely enigmatic. Here, we report the cryoelectron microscopy (cryo-EM) structure of an apoptotic holoenzyme and structure-guided biochemical analyses. The caspase recruitment domains (CARDs) of Apaf-1 and caspase-9 assemble in two different ways: a 4:4 complex docks onto the central hub of the apoptosome, and a 2:1 complex binds the periphery of the central hub. The interface between the CARD complex and the central hub is required for caspase-9 activation within the holoenzyme. Unexpectedly, the CARD of free caspase-9 strongly inhibits its proteolytic activity. These structural and biochemical findings demonstrate that the apoptosome activates caspase-9 at least in part through sequestration of the inhibitory CARD domain.
Mechanistic insights into caspase-9 activation by the structure of the apoptosome holoenzyme.,Li Y, Zhou M, Hu Q, Bai XC, Huang W, Scheres SH, Shi Y Proc Natl Acad Sci U S A. 2017 Feb 14;114(7):1542-1547. doi:, 10.1073/pnas.1620626114. Epub 2017 Jan 31. PMID:28143931[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Hu Y, Benedict MA, Ding L, Nunez G. Role of cytochrome c and dATP/ATP hydrolysis in Apaf-1-mediated caspase-9 activation and apoptosis. EMBO J. 1999 Jul 1;18(13):3586-95. PMID:10393175 doi:10.1093/emboj/18.13.3586
- ↑ Ogawa T, Shiga K, Hashimoto S, Kobayashi T, Horii A, Furukawa T. APAF-1-ALT, a novel alternative splicing form of APAF-1, potentially causes impeded ability of undergoing DNA damage-induced apoptosis in the LNCaP human prostate cancer cell line. Biochem Biophys Res Commun. 2003 Jun 27;306(2):537-43. PMID:12804598
- ↑ Li Y, Zhou M, Hu Q, Bai XC, Huang W, Scheres SH, Shi Y. Mechanistic insights into caspase-9 activation by the structure of the apoptosome holoenzyme. Proc Natl Acad Sci U S A. 2017 Feb 14;114(7):1542-1547. doi:, 10.1073/pnas.1620626114. Epub 2017 Jan 31. PMID:28143931 doi:http://dx.doi.org/10.1073/pnas.1620626114
