Characterizing and exploiting "allosteric crosstalk" amongst pain receptors

About This Grant

PROJECT SUMMARY Opioid receptors not only mediate pain relief but also act as the targets of potent exogenous opioids that are devastatingly addictive and cause overdose deaths. The principal target for both analgesia and addiction of exogenous opioids is the µ-opioid receptor (µOR). While traditionally thought to be regulated exclusively by opioids, recent work from our group has detailed an unexpected layer of complexity: endogenous neuromodulators such as endocannabinoids and oxytocin – classically associated with their own independently signaling receptors that regulate mood, pain, inflammation, and social behavior – can directly work to allosterically modulate µOR signaling. This unanticipated ligand-mediated crosstalk opens an entirely new dimension in opioid receptor pharmacology and suggests that targeting these pathways could yield novel interventions for opioid use disorder (OUD) and related conditions. The central goal of this project is to elucidate, at atomic resolution, the molecular mechanisms by which endogenous neuromodulators influence µOR structure and function. We will employ state-of-the-art cryo-electron microscopy (cryoEM) approaches to determine high- resolution structures of µOR in both its active and inactive states, bound to cannabinoids and neuropeptides like oxytocin. Critically, we will advance methodological innovations in time-resolved cryoEM to directly visualize the intermediate conformational states and the full activation/inactivation pathway of the receptor as it transitions between these endpoints. This will allow us, for the first time, to construct “molecular movies” that reveal the stepwise mechanisms by which natural modulators influence receptor activation, allostery, and signaling bias. Through these detailed structural insights, we aim to identify previously unrecognized allosteric sites and intermediate states that serve as "control points" for selective pharmacological intervention. These discoveries will inform the rational design of new therapeutic strategies that harness or mimic the brain’s own modulatory systems, offering a pathway to safer, more targeted treatments for OUD, pain, and overdose. In summary, this project will not only clarify the molecular basis of opioid receptor regulation in the brain, but will also set the stage for mechanism-driven drug discovery to address the current opioid crisis and advance our broader understanding of GPCR biology.