Article

Activation of Apoptosis in Vivo by a Hydrocarbon-Stapled BH3 Helix

Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, United States
Science (Impact Factor: 33.61). 10/2004; 305(5689):1466-70. DOI: 10.1126/science.1099191
Source: PubMed

ABSTRACT

BCL-2 family proteins constitute a critical control point for the regulation of apoptosis. Protein interaction between BCL-2
members is a prominent mechanism of control and is mediated through the amphipathic α-helical BH3 segment, an essential death
domain. We used a chemical strategy, termed hydrocarbon stapling, to generate BH3 peptides with improved pharmacologic properties.
The stapled peptides, called “stabilized alpha-helix of BCL-2 domains” (SAHBs), proved to be helical, protease-resistant,
and cell-permeable molecules that bound with increased affinity to multidomain BCL-2 member pockets. A SAHB of the BH3 domain
from the BID protein specifically activated the apoptotic pathway to kill leukemia cells. In addition, SAHB effectively inhibited
the growth of human leukemia xenografts in vivo. Hydrocarbon stapling of native peptides may provide a useful strategy for
experimental and therapeutic modulation of protein-protein interactions in many signaling pathways.

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    • "Despite the contrasts with the b-arrestin/b-adaptin 2 PPI and with our recommendations , we share the interpretation that the stabilization of a helices is not a requirement for the design of peptide inhibitors (photoswitchable or not) of PPIs mediated by a helix. Regarding this issue, another study questions the effect of stabilization of the helix by stapling in the BimBH3/Bcl-2 PPI (Okamoto et al., 2013), a classic example where stapled peptides were tested previously (Walensky et al., 2004). "
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    ABSTRACT: Many protein-protein interactions (PPIs) are mediated by short, often helical, linear peptides. Molecules mimicking these peptides have been used to inhibit their PPIs. Recently, photoswitchable peptides with little secondary structure have been developed as modulators of clathrin-mediated endocytosis. Here we perform a systematic analysis of a series of azobenzene-crosslinked peptides based on a β-arrestin P-long 20-mer peptide (BAP-long) sequence to assess the relevance of secondary structure in their interaction with β-adaptin 2 and to identify the design requirements for photoswitchable inhibitors of PPI (PIPPIs). We observe that flexible structures show a greater inhibitory capacity and enhanced photoswitching ability and that the absence of helical structures in free inhibitor peptide is not a limitation for PIPPI candidates. Therefore, our PIPPIs expand the field of potential inhibitors of PPIs to the wide group of flexible peptides, and we argue against using a stable secondary structure as a sole criterion when designing PIPPI candidates. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Full-text · Article · Jan 2015 · Chemistry & Biology
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    • "Accumulated structural data has also revealed that a staple can interact with its target via multiple mechanisms [63]. In 2004, Walensky et al. demonstrated that the all-hydrocarbon stapled a-helical BID BH3 segment was protease resistant, cell-permeable, and showed in vitro and in vivo biological activity [61]. During the following decade, stapled peptide technology has been applied to a number of extra-and intracellular targets, including most intractable transcription factors and other promoters of cancer proliferation [61,64e67]. "
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    ABSTRACT: Rapid advancements in genomics have brought a better understanding of molecular mechanisms for various pathologies and identified a number of highly attractive target classes. Some of these targets include intracellular protein-protein interactions (PPIs), which control many essential biological pathways. Their surfaces are part of a diverse and unexplored biological space, where traditional small molecule scaffolds are not always successful. While large biologics can effectively modulate PPIs in the extracellular region, their limitation in crossing the cellular membrane leaves intracellular protein targets outside of their reach. There is a growing need in the pharmaceutical field to push the boundaries of traditional drug design and discover innovative molecules that are able to modulate key biological pathways by inhibiting intracellular PPIs. Peptides are one of the most promising classes of molecules that could deliver such therapeutics in the near future. In this review, we describe technological advancements and emerging chemical approaches for stabilizing active peptide conformations, including stapling, hydrogen bond surrogates, beta-hairpin mimetics, grafting on stable scaffolds, and macrocyclization. These design strategies carry the promise of opening the doors for peptide therapeutics to reach the currently "undruggable" space. Copyright © 2015 Elsevier Masson SAS. All rights reserved.
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    • "We recently demonstrated that stapled peptide analogues of Nutlin targeting Mdm2 are able to bind and inhibit both wild type and the M62A/Q24R resistant variants in biophysical and cell-based assays [18], [19]. Stapled peptides comprise a covalent linkage bridging adjacent turns of an alpha helical peptide (the “staple”) [20]. By pre-stabilising favourably interacting conformer(s), the staple increases affinity by reducing the entropic penalty of binding. "
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    ABSTRACT: As key negative regulator of the p53 tumour suppressor, Mdm2 is an attractive therapeutic target. Small molecules such as Nutlin have been developed to antagonise Mdm2, resulting in p53-dependent death of tumour cells. We have recently described a mutation in Mdm2 (M62A), which precludes binding of Nutlin, but not p53. This Nutlin-resistant variant is not, however, refractory to binding and inhibition by stapled peptide antagonists targeting the same region of Mdm2. A detailed understanding of how stapled peptides are recalcitrant to Mdm2 mutations conferring Nutlin-resistance will aid in the further development of potent Mdm2 antagonists. Here, we report the 2.00 Å crystal structure of a stapled peptide antagonist bound to Nutlin resistant Mdm2. The stapled peptide relies on an extended network of interactions along the hydrophobic binding cleft of Mdm2 for high affinity binding. Additionally, as seen in other stapled peptide structures, the hydrocarbon staple itself contributes to binding through favourable interactions with Mdm2. The structure highlights the intrinsic plasticity present in both Mdm2 and the hydrocarbon staple moiety, and can be used to guide future iterations of both small molecules and stapled peptides for improved antagonists of Mdm2.
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