Background: Intracellular parts of GPCRs have yet to be effectively exploited as allosteric modulators. Results: The structure and mechanism of action of a lipidated pepducin agonist is determined. Conclusion:The pepducin requires the H8 helix and TM7 tyrosine propeller to stabilize the on-state and trigger receptor-G protein signaling. Significance: This work provides critical insight into the identification of allosteric modulators to this major drug target class.

EHD1 mediates long-loop recycling of many receptors by forming signaling complexes using its EH domain. We report the design and optimization of cyclic peptides as ligands for the EH domain of EHD1. We demonstrate that the improved affinity from cyclization allows fluorescence-based screening applications for EH domain inhibitors. The cyclic peptide is also unusually well-structured in aqueous solution, as demonstrated using nuclear magnetic resonance-based structural models. Because few EH domain inhibitors have been described, these more potent inhibitors will improve our understanding of the roles of EHD1 in the context of cancer invasion and metastasis.

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