title: Solid phase synthesis of Smac/DIABLO-derived peptides using a 'Safety-Catch' resin: identification of potent XIAP BIR3 antagonists.
abstract: The N-terminal sequence of the Smac/DIABLO protein is known to be involved in binding to the BIR3 domain of the anti-apoptotic proteins IAPs, antagonizing their action. Short peptides and peptide mimetics based on the first 4-residues of Smac/DIABLO have been demonstrated to re-sensitize resistant cancer cells, over-expressing IAPs, to apoptosis. Based on the well-defined structural basis for this interaction, a small focused library of C-terminal capped Smac/DIABLO-derived peptides was designed in silico using docking to the XIAP BIR3 domain. The top-ranked computational hits were conveniently synthesized employing Solid Phase Synthesis (SPS) on an alkane sulfonamide 'Safety-Catch' resin. This novel approach afforded the rapid synthesis of the target peptide library with high flexibility for the introduction of various C-terminal amide-capping groups. The library members were obtained in high yield (>65%) and purity (>85%), upon nucleophilic release from the activated resin by treatment with various amine nucleophiles. In vitro caspase-9 activity reconstitution assays of the peptides in the presence of the recombinant BIR3-domain of human XIAP (500nM) revealed N-methylalanyl-tertiarybutylglycinyl-4-(R)-phenoxyprolyl-N-biphenylmethyl carboxamide (11a) to be the most potent XIAP BIR3 antagonist of the series synthesized inducing 93% recovery of caspase-9 activity, when used at 1μM concentration. Compound (11a) also demonstrated moderate cytotoxicity against the breast cancer cell lines MDA-MB-231 and MCF-7, compared to the Smac/DIABLO-derived wild-type peptide sequences that were totally inactive in the same cell lines.
authors.affiliation: School of Pharmacy, Queen's University of Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK.
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Elsawy
authors.forename: Lorraine
authors.initials: L
authors.lastname: Martin
authors.forename: Irina G
authors.initials: IG
authors.lastname: Tikhonova
authors.forename: Brian
authors.initials: B
authors.lastname: Walker
mesh_terms: D051017:Apoptosis Regulatory Proteins; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry*; D061986:MCF-7 Cells; D008872:Microwaves; D024101:Mitochondrial Proteins / Q000737:chemistry*; D010455:Peptides / Q000138:chemical synthesis* / Q000633:toxicity; D057786:Peptidomimetics; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D012117:Resins, Synthetic / Q000737:chemistry; D060327:Solid-Phase Synthesis Techniques; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D010455:Peptides; D057786:Peptidomimetics; D011994:Recombinant Proteins; D012117:Resins, Synthetic; D051636:X-Linked Inhibitor of Apoptosis Protein; D053453:Caspase 9
keywords: Apoptosis; Cancer resistance; Peptidomimetics; SPPS; Safety-Catch resin; Smac/DIABLO; XIAP BIR3