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. 2017 Jan 12;8(1):e2543.
doi: 10.1038/cddis.2016.469.

Structural insight into an evolutionarily ancient programmed cell death regulator - the crystal structure of marine sponge BHP2 bound to LB-Bak-2

Sofia Caria  1 , Mark G Hinds  2 , Marc Kvansakul  1
Affiliations

Structural insight into an evolutionarily ancient programmed cell death regulator - the crystal structure of marine sponge BHP2 bound to LB-Bak-2

Sofia Caria et al. Cell Death Dis. .

Abstract

Sponges of the porifera family harbor some of the evolutionary most ancient orthologs of the B-cell lymphoma-2 (Bcl-2) family, a protein family critical to regulation of apoptosis. The genome of the sponge Geodia cydonium contains the putative pro-survival Bcl-2 homolog BHP2, which protects sponge tissue as well as mammalian Hek-293 and NIH-3T3 cells against diverse apoptotic stimuli. The Lake Baikal demosponge Lubomirskia baicalensis has been shown to encode both putative pro-survival Bcl-2 (LB-Bcl-2) and pro-apoptotic Bcl-2 members (LB-Bak-2), which have been implied in axis formation (branches) in L. baicalensis. However, the molecular mechanism of action of sponge-encoded orthologs of Bcl-2 remains to be clarified. Here, we report that the pro-survival Bcl-2 ortholog BHP2 from G. cydonium is able to bind the BH3 motif of a pro-apoptotic Bcl-2 protein, LB-Bak-2 of the sponge L. baicalensis. Furthermore, we determined the crystal structure of BHP2 bound to LB-Bak-2, which revealed that using a binding groove conserved across all pro-survival Bcl-2 proteins, BHP2 binds multi-motif Bax-like proteins through their BH3-binding regions. However, BHP2 discriminates against BH3-only bearing proteins by blocking access to a hydrophobic pocket that is critical for BH3 motif binding in pro-survival Bcl-2 proteins from higher organisms. This differential binding mode is reflected in a structure-based phylogenetic comparison of BHP2 with other Bcl-2 family members, which revealed that BHP2 does not cluster with either Bcl-2 members of higher organisms or pathogen-encoded homologs, and assumes a discrete position. Our findings suggest that the molecular machinery and mechanisms for executing Bcl-2-mediated apoptosis as observed in mammals are evolutionary ancient, with early regulation of apoptotic machineries closely resembling their modern counterparts in mammals rather than Caenorhabditis elegans or drosophila.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
BHP2 interactions with BH3 domain peptides of pro-apoptotic Bcl-2 proteins. The affinity of recombinant BHP2 for BH3 domain peptides (26-mers, except for a Bax 28-mer and a Bid 34-mer) was assessed using isothermal titration calorimetry. KD values (in nM) are the means of three experiments±S.D. NB, no binding detected, N denotes stoichiometry
Figure 2
Figure 2
Crystal structure of BHP2 bound to LB-Bak-2 BH3 domain. (a) BHP2 (pink) in complex with the LB-Bak-2 BH3 domain (violet). BHP2 helices are labeled α1–8. The view in (a) is into the hydrophobic binding groove formed by helices α3–5. (b) Bcl-xL (cyan) in complex with the Bim BH3 domain (orange). The view is as in (a). (c) Vaccinia virus F1L (sand) in complex with the Bak BH3 domain (green).45 The view is as in (a). (d) CED9 (blue) in complex with the EGL1 BH3 domain (yellow). The view is as in (a).
Figure 3
Figure 3
Detailed view of the helix turn in the BHP2 α1/α2 loop. BHP2 (pink) main chain is shown as cartoon. BHP2 residues comprising the ordered α1/α2 loop segment are shown as magenta
Figure 4
Figure 4
(a) Detailed view of the BHP2:LB-Bak-2 BH3 interface. The BHP2 surface, backbone and binding groove are shown in gray and pink respectively, whereas LB-Bak-2 BH3 is shown in violet. The four key hydrophobic residues of LB-Bak-2 (V71, L75, F78 and V82) on protruding into the binding groove, and the conserved salt bridge formed by LB-Bak D80 and BHP2 R135 are labeled, as well as residues involved in hydrogen bonds. Comparison of the P3 pocket among pro-survival Bcl-2: pro-apoptotic BH3 domain complexes. (b) BHP2:LB-Bak-2 complex. (c) Bcl-xL:Bim complex. (d) CED9:EGL1 complex. (e) F1L:Bak complex
Figure 5
Figure 5
(a) Sequence alignment of BHP2 with pro-survival Bcl-2 family members. (b) Sequence alignment of BH3 domains of LB-Bak-2 and human pro-apoptotic Bcl-2 proteins. (c) Structure-based phylogenetic analysis of pro-survival Bcl-2 proteins of known structure
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References

    1. Lasi M, David CN, Bottger A. Apoptosis in pre-Bilaterians: hydra as a model. Apoptosis 2010; 15: 269–278. - PubMed
    1. Koziol C, Borojevic R, Steffen R, Muller WE. Sponges (Porifera) model systems to study the shift from immortal to senescent somatic cells: the telomerase activity in somatic cells. Mech Ageing Dev 1998; 100: 107–120. - PubMed
    1. Zmasek CM, Godzik A. Evolution of the animal apoptosis network. Cold Spring Harb Perspect Biol 2013; 5: a008649. - PMC - PubMed
    1. Vaux DL, Haecker G, Strasser A. An evolutionary perspective on apoptosis. Cell 1994; 76: 777–779. - PubMed
    1. Adams JM, Cory S. The Bcl-2 protein family: arbiters of cell survival. Science 1998; 281: 1322–1326. - PubMed

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