Thioether Analogues of Disulfide‐Bridged Cyclic Peptides Targeting Death Receptor 5: Conformational Analysis, Dimerisation and Consequences for Receptor Activation

Abstract

Cyclic peptides containing redox-stable thioether bridges might provide a useful alternative to disulfide-bridged bioactive peptides. We report the effect of replacing the disulfide bridge with a lanthionine linkage in a 16-mer cyclic peptide that binds to death receptor 5 (DR5, TRAIL-R2). Upon covalent oligomerisation, the disulfide-bridged peptide has previously shown similar behaviour to that of TNF-related apoptosis inducing ligand (TRAIL), by selectively triggering the DR5 cell death pathway. The structural and biological properties of the DR5-binding peptide and its desulfurised analogue were compared. Surface plasmon resonance (SPR) data suggest that these peptides bind DR5 with comparable affinities. The same holds true for dimeric versions of these peptides: the thioether is able to induce DR5-mediated apoptosis of BJAB lymphoma and tumorigenic BJELR cells, albeit to a slightly lower extent compared to its disulfide homologue. NMR analysis revealed subtle variation in the conformations of the two peptides and suggests that the thioether peptide is slightly less folded than its disulfide homologue. These observations could account for the different capability of the two dimers to cluster DR5 receptors on the cell surface and to trigger apoptosis. Nevertheless, our results suggest that the thioether peptide is a potential candidate for evaluation in animal models.

Anti-metastatic effect of the TM4SF5-specific peptide vaccine and humanized monoclonal antibody on colon cancer in a mouse lung metastasis model

“…Investigators generally make cyclic peptides using disulfide bridges between near cysteine residues. Recently, investigators improved the cyclization efficiency by C-terminal modification and established thioether analogues of disulfide-bridged cyclic peptides, and demonstrated anti-cancer effects of the cyclic peptides [26, 27]. …”

Redox‐stable cyclic peptide inhibitors of the SPSB2–iNOS interaction

“…There have been reports of disulphide replacements with thioethers [5][6][7][8], dicarba bridges [9,10] and diselenides [11] to generate redox-stable analogues without significantly compromising the binding affinity or activity of the parent peptide. However, it cannot be assumed a priori that replacement of a disulphide with a thioether will necessarily return biologically active compounds and each example needs to be investigated in a context-and sequence-specific manner.…”

Anti-Infective Peptides to Enhance the Host Innate Response: Design, Development and Delivery

“…While disulfide bridges can form in the cytoplasm under oxidative stress [29], for example during infection, cyclic peptide analogues that are stable to the normally reducing conditions of the cell cytoplasm would be likely to be more effective. While the backbone-cyclized peptide 2 eliminated the disulfide bridge, disulfides can also be replaced with thioethers [30][31][32][33], dicarba-bridges [34,35] and di-selenides [36] to generate redox-stable analogues. Therefore, an analogue of 1 was designed in which the disulfide bridge was replaced with a thioether linkage.…”