Designing allosteric modulators to change GPCR G protein subtype selectivity

Abstract

G-protein-coupled receptors (GPCRs) convert extracellular signals into intracellular responses by signalling through 16 subtypes of Gα proteins and two β-arrestin proteins. Biased compounds—molecules that preferentially activate a subset of these proteins—engage therapy-relevant pathways more selectively1 and promise to be safer, more effective medications than compounds that uniformly activate all pathways2. However, the determinants of bias are poorly understood, and we lack rationally designed molecules that select for specific G proteins. Here, using the prototypical class A GPCR neurotensin receptor 1 (NTSR1), we show that small molecules that bind to the intracellular GPCR–transducer interface change G protein coupling by subtype-specific and predictable mechanisms, enabling structure-guided drug design. We find that the intracellular, core-binding compound SBI-553 switches the G protein preference of NTSR1 through direct intermolecular interactions3, 4–5, promoting or preventing association with specific G protein subtypes. Modifications to the SBI-553 scaffold produce allosteric modulators with distinct G protein selectivity profiles. Selectivity profiles are probe independent, conserved across species and translate to differences in activity in vivo. Our studies show that G protein selectivity can be tailored with small changes to a single chemical scaffold targeting the receptor–transducer interface. Moreover, given that this pocket is broadly conserved, our findings could provide a strategy for pathway-selective drug discovery that is applicable to the diverse GPCR superfamily.