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: Mohamed A Elsawy, Lorraine Martin, Irina G Tikhonova, Brian Walker
• Journal: Bioorganic & medicinal chemistry (Bioorg Med Chem) Vol. 21 Issue 17 Pg. 5004-11 (Sep 01 2013) ISSN: 1464-3391 [Electronic] England
• PMID: 23886811 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2013 Elsevier Ltd. All rights reserved.

Chemical References

• Apoptosis Regulatory Proteins
• DIABLO protein, human
• Intracellular Signaling Peptides and Proteins
• Mitochondrial Proteins
• Peptides
• Peptidomimetics
• Recombinant Proteins
• Resins, Synthetic
• X-Linked Inhibitor of Apoptosis Protein
• Caspase 9

Topics

• Apoptosis Regulatory Proteins
• Caspase 9 (metabolism)
• Cell Line, Tumor
• Cell Survival (drug effects)
• Humans
• Intracellular Signaling Peptides and Proteins (chemistry)
• MCF-7 Cells
• Microwaves
• Mitochondrial Proteins (chemistry)
• Peptides (chemical synthesis, toxicity)
• Peptidomimetics
• Protein Structure, Tertiary
• Recombinant Proteins (biosynthesis, chemistry, genetics)
• Resins, Synthetic (chemistry)
• Solid-Phase Synthesis Techniques
• X-Linked Inhibitor of Apoptosis Protein (antagonists & inhibitors, genetics, metabolism)