α/β-Peptide Foldamers Targeting Intracellular Protein-Protein Interactions with Activity in Living Cells

J Am Chem Soc. 2015 Sep 9;137(35):11365-75.

Checco JW, Lee EF^1,2, Evangelista M¹, Sleebs NJ¹, Rogers K^1,2, Pettikiriarachchi A¹, Kershaw NJ^1,2, Eddinger GA, Belair DG, Wilson JL, Eller CH, Raines RT,Murphy WL, Smith BJ³, Gellman SH, Fairlie WD^1,2.

Author information

• ¹The Walter and Eliza Hall Institute of Medical Research , Parkville, Victoria 3052, Australia.
• ²Department of Medical Biology, University of Melbourne , Parkville, Victoria 3010, Australia.
• ³Department of Chemistry and Physics, La Trobe Institute of Molecular Science , Melbourne, Victoria 3086, Australia.

Abstract:

Peptides can be developed as effective antagonists of protein-protein interactions, but conventional peptides (i.e., oligomers of l-α-amino acids) suffer from significant limitations in vivo. Short half-lives due to rapid proteolytic degradation and an inability to cross cell membranes often preclude biological applications of peptides. Oligomers that contain both α- and β-amino acid residues ("α/β-peptides") manifest decreased susceptibility to proteolytic degradation, and when properly designed these unnatural oligomers can mimic the protein-recognition properties of analogous "α-peptides". This report documents an extension of the α/β-peptide approach to target intracellular protein-protein interactions. Specifically, we have generated α/β-peptides based on a "stapled" Bim BH3 α-peptide, which contains a hydrocarbon cross-link to enhance α-helix stability. We show that a stapled α/β-peptide can structurally and functionally mimic the parent stapled α-peptide in its ability to enter certain types of cells and block protein-protein interactions associated with apoptotic signaling. However, the α/β-peptide is nearly 100-fold more resistant to proteolysis than is the parent stapled α-peptide. These results show that backbone modification, a strategy that has received relatively little attention in terms of peptide engineering for biomedical applications, can be combined with more commonly deployed peripheral modifications such as side chain cross-linking to produce synergistic benefits.