Abstract SY06-03: Stapled helical peptides to dissect and target oncogenic protein interactions.

Protein interactions mediate innumerable cellular activities in health and disease. Whether fleeting or stable, homeostatic or pathologic, protein partnerships and their sites of contact form the basis for discovery of biological pathways, disease mechanisms, and opportunities for therapeutic intervention. The peptide alpha-helix represents one of nature9s most featured protein shapes and is employed in a diversity of protein architectures, from the cytoskeletal infrastructure to the most intimate contact points between crucial signaling proteins. Harnessing nature9s evolutionarily-honed peptide helices to investigate and subvert disease-causing protein interactions has been hindered by their loss of natural architecture, vulnerability to degradation, and cellular impermeability. We have applied a chemical strategy termed "hydrocarbon-stapling" to remedy the shortcomings of synthetic peptides, yielding unique discovery tools and prototype therapeutics that target pathologic protein interactions for potential clinical benefit. Here, we describe a multidisciplinary approach to the production and application of these reagents for protein interaction research and therapeutic targeting. Through facile derivatization and functionalization steps, stabilized alpha-helices (SAHs) can be tailored for a broad range of applications in biochemical, structural, proteomic, cellular, and in vivo studies. The track record of SAHs in uncovering new protein interactions and suppressing tumor growth in preclinical models speaks to their dual capacity to serve as effective research tools and promising drug prototypes. For example, we have deployed SAHs to structurally define the elusive activation site on an essential executioner protein of the cell death pathway, uncover an unanticipated function for a death protein in metabolism, identify a natural alpha-helical peptide that can function as an exclusive inhibitor of a formidable anti-apoptotic protein linked to cancer, remedy the proteolytic instability of lengthy peptide therapeutics, define the key conformational changes that transform an inactive death protein into a toxic mitochondrial oligomer, and recapitulate the essential features of key transcription factor motifs to reactivate tumor suppressor pathways in cancer cells. As with all new technologies, we continue to learn the rules, make improvements, and discover new applications, with the goal of expanding both the accessibility and utility of stapled peptides. We find that a commitment to taking a rigorous, stepwise, and iterative approach to the production, optimization, and application of stapled peptides is the best formula for success in developing these reagents as next-generation research tools and prototype therapies. Citation Format: Loren D. Walensky. Stapled helical peptides to dissect and target oncogenic protein interactions. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr SY06-03. doi:10.1158/1538-7445.AM2013-SY06-03