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. 2010 Nov;11(11):841-7.
doi: 10.1038/embor.2010.141. Epub 2010 Oct 1.

Crystal structures of human caspase 6 reveal a new mechanism for intramolecular cleavage self-activation

Xiao-Jun Wang  1 , Qin Cao, Xiang Liu, Kai-Tuo Wang, Wei Mi, Yan Zhang, Lan-Fen Li, Andrea C LeBlanc, Xiao-Dong Su
Affiliations

Crystal structures of human caspase 6 reveal a new mechanism for intramolecular cleavage self-activation

Xiao-Jun Wang et al. EMBO Rep. 2010 Nov.

Abstract

Dimeric effectors caspase 3 and caspase 7 are activated by initiator caspase processing. In this study, we report the crystal structures of effector caspase 6 (CASP6) zymogen and N-Acetyl-Val-Glu-Ile-Asp-al-inhibited CASP6. Both of these forms of CASP6 have a dimeric structure, and in CASP6 zymogen the intersubunit cleavage site (190)TEVD(193) is well structured and inserts into the active site. This positions residue Asp 193 to be easily attacked by the catalytic residue Cys 163. We demonstrate biochemically that intramolecular cleavage at Asp 193 is a prerequisite for CASP6 self-activation and that this activation mechanism is dependent on the length of the L2 loop. Our results indicate that CASP6 can be activated and regulated through intramolecular self-cleavage.

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Conflict of interest statement

The authors declare that they have no conflict of interest.

Figures

Figure 1
Figure 1
Structures of the caspase 6. (A,B) The overall dimeric structures of (A) CASP6 zymogen and (B) Ac-VEID-CHO-inhibited CASP6. The dashed lines indicate unobserved flexible residues. (C) The electron density map (2fo–fc maps) surrounding the L2 loop shown at 1.0 σ, calculated by phenix.refine. (D,E) Active sites of (D) CASP6 zymogen and (E) Ac-VEID-CHO-inhibited CASP6. The 190TEVD193 is shown in yellow and the hydrogen bonds and ‘salt bridges' are represented by black dashed lines. (F) Active sites overlay of CASP6 zymogen and Ac-VEID-CHO-inhibited CASP6. Ac-VEID-CHO, N-Acetyl-Val-Glu-Ile-Asp-al.
Figure 2
Figure 2
Biochemical evidence for caspase 6 intramolecular self-activation. (A) Schematic diagram of CASP6. (B–I) Coomassie-blue-stained gels showing proCASP6C163A cleaved by 1% active (B) CASP6 or (C) CASP3, (D) proCASP6C163AD179A cleaved by 1% active CASP3, proCASP6 incubated (E) with or (F) without 1% active CASP6, proCASP6C163A,R(64,220)E cleaved by 1% active CASP6 in (G) 1 h and (H) 24 h, and (I) self-processed activity of purified WT or CASP6 mutants. The 25-kDa unlabelled bands in (D) were a bacterial contaminated protein. The asterisk in I shows this band was pro-p20 (supplementary Figs S5 and S6 online). FL, full-length CASP6; L, intersubunit linker; p10, small subunit; p20, large subunit; pro, pro-domain; WT, wild type.
Figure 3
Figure 3
Intramolecular cleavage of caspase 6 at Asp 193 depends on the length of the L2 loop. (A) Sequence alignment of the L2 loop region for effectors. The catalytic cysteines are shadowed in blue, and the intersubunit cleavage sites indicated by scissors are in pink and orange. The 190TEVD193 of CASP6 is highlighted in yellow. (B) Overlay of CASP6 and CASP7 zymogens. The dashed lines refer to the unobserved flexible residues. (C,D) Western blot analyses of bacterially expressed wild type or mutant CASP6 showing auto-activation from (C) 0 to 4 h or (D) after 4 h.
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References

    1. Adams PD, Grosse-Kunstleve RW, Hung LW, Ioerger TR, McCoy AJ, Moriarty NW, Read RJ, Sacchettini JC, Sauter NK, Terwilliger TC (2002) PHENIX: building new software for automated crystallographic structure determination. Acta Crystallogr D Biol Crystallogr 58: 1948–1954 - PubMed
    1. Albrecht S, Bourdeau M, Bennett D, Mufson EJ, Bhattacharjee M, LeBlanc AC (2007) Activation of caspase-6 in aging and mild cognitive impairment. Am J Pathol 170: 1200–1209 - PMC - PubMed
    1. Allsopp TE, McLuckie J, Kerr LE, Macleod M, Sharkey J, Kelly JS (2000) Caspase 6 activity initiates caspase 3 activation in cerebellar granule cell apoptosis. Cell Death Differ 7: 984–993 - PubMed
    1. Baliga BC, Colussi PA, Read SH, Dias MM, Jans DA, Kumar S (2003) Role of prodomain in importin-mediated nuclear localization and activation of caspase-2. J Biol Chem 278: 4899–4905 - PubMed
    1. Baumgartner R, Meder G, Briand C, Decock A, D'Arcy A, Hassiepen U, Morse R, Renatus M (2009) The crystal structure of caspase-6, a selective effector of axonal degeneration. Biochem J 423: 429–439 - PubMed

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