Events Calendar

Title: “Development of a Scalable Yeast-Based Functional Selection Platform to Enable the Discovery of Diverse Protein-Based G Protein-Coupled Receptor Modulators”

Advisory Committee: Mo Khalil, PhD – BU BME (Advisor) John Ngo, PhD – BU BME (Chair) Chang Liu, PhD – UC Irvine BME Wilson Wong, PhD – BU BME Juan Fuxman Bass, PhD – BU Biology

Abstract: G protein-coupled receptors (GPCRs) are one of the most common signaling structures in the human body and control numerous physiological processes including vision, olfaction, neurotransmission, nutrient metabolism, and body homeostasis. Accordingly, 1/3 of all FDA approved drugs target GPCRs; yet, more than 75% of all non-olfactory GPCRs, including many well-validated drug targets, remain undrugged. This drug discovery gap is largely due to three reasons: off-target drug action at GPCRs closely related to the target, on-target effects at undesired tissues, and poor drug pharmacokinetics. Protein-based GPCR therapeutics, with their exquisite specificity and robust pharmacokinetics, have been long sought to overcome these challenges, but current binder discovery methodologies struggle to uncover the rare protein variants capable of precisely modulating GPCRs and eliciting desired downstream signals. Here we leverage directed evolution to discover functional protein-based therapeutic leads for difficult GPCR targets entirely within engineered cells, thereby avoiding the onerous receptor purification and structure determination or animal immunization that is typically required for GPCR drug discovery. To achieve this, we functionally reconstituted several human GPCRs into Saccharomyces cerevisiae and created genetic circuits that couple receptor activation to expression of growth-selectable markers. We then co-expressed protein libraries that are tethered proximal to the receptors where they can activate receptor signaling, allowing us to select for library members that modulate the GPCRs simply by growing the cells in selective media. We then purified hit proteins and validated both receptor activity and selectivity first in yeast and then in mammalian cell assays. This platform provides a novel, flexible approach for discovering candidate protein-based therapeutics against difficult-to-drug yet important GPCR targets.