{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T10:18:35Z","timestamp":1785406715017,"version":"3.56.0"},"posted":{"date-parts":[[2026,2,21]]},"group-title":"Biophysics","reference-count":41,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,2,21]],"date-time":"2026-02-21T00:00:00Z","timestamp":1771632000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"funder":[{"id":[{"id":"https:\/\/ror.org\/04f6cgz95","id-type":"ROR","asserted-by":"publisher"}]},{"id":[{"id":"https:\/\/ror.org\/013kjyp64","id-type":"ROR","asserted-by":"publisher"}]},{"id":[{"id":"https:\/\/ror.org\/00knt4f32","id-type":"ROR","asserted-by":"publisher"}]},{"award":["R01DA036246"],"award-info":[{"award-number":["R01DA036246"]}],"id":[{"id":"https:\/\/ror.org\/01cwqze88","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"crossref","award":["22425701"],"award-info":[{"award-number":["22425701"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100012166","name":"National Key R&D Program of China","doi-asserted-by":"crossref","award":["2024YFA0916700"],"award-info":[{"award-number":["2024YFA0916700"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100012166","name":"National Key R&D Program of China","doi-asserted-by":"crossref","award":["2024YFA1306200"],"award-info":[{"award-number":["2024YFA1306200"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"crossref","id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"crossref"}]},{"award":["DA059978"],"award-info":[{"award-number":["DA059978"]}],"id":[{"id":"https:\/\/ror.org\/01cwqze88","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,2,21]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:p>Opioid agonists such as morphine and fentanyl exert analgesic effects by binding and activating the \u00b5-opioid receptor (\u00b5OR), yet agonism of the \u00b5OR causes a slate of serious side effects. \u00b5OR-mediated addiction and respiratory depression are the major causes of the current opioid overdose crisis, largely driven by the explosion in illicit use of fentanyl, a potent opioid receptor full agonist. Given these serious side effects (and high resulting societal cost), molecules that act as analgesics with distinct mechanisms of action are of great interest. Positive allosteric modulators (PAMs) of the \u00b5OR have the potential to avoid many off-target side effects of conventional opioid orthosteric agonists by enhancing the signaling properties of natural opioid peptide systems. We used a DNA-encoded chemical library screening approach to selectively discover active-state-specific \u00b5OR PAMs. Two out of 3 selected prospective PAMs displayed the anticipated enhancement in agonist activity. The most effective of these compounds enhanced the activity of all orthosteric opioid agonists tested, including the native opioid peptide met-enkephalin. Little is known about the underlying dynamic basis of allosteric modulation of Family A GPCRs like the \u00b5OR. To that end, we used single-molecule fluorescence resonance energy transfer experiments to detail the impact that our novel \u00b5OR PAM has on the dynamic activation behavior of a key region on the intracellular face of the receptor. Our results here provide both a new chemical scaffold that acts as a \u00b5OR PAM and detailed pharmacological and dynamic insights into its mechanism of action.<\/jats:p>","DOI":"10.64898\/2026.02.20.707058","type":"posted-content","created":{"date-parts":[[2026,2,22]],"date-time":"2026-02-22T04:20:14Z","timestamp":1771734014000},"source":"Crossref","is-referenced-by-count":1,"title":["Discovery and dynamic pharmacology of \u00b5-opioid receptor positive allosteric modulators"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2260-7722","authenticated-orcid":false,"given":"Evan S.","family":"O\u2019Brien","sequence":"first","affiliation":[{"name":"Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Junzheng","family":"Wang","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Membrane Biology, Beijing 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USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2283-4033","authenticated-orcid":false,"given":"Kaavya","family":"Krishna Kumar","sequence":"additional","affiliation":[{"name":"Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Weijiao","family":"Huang","sequence":"additional","affiliation":[{"name":"Department of Molecular and Cellular Physiology, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Susruta","family":"Majumdar","sequence":"additional","affiliation":[{"name":"Center for Clinical Pharmacology, Department of Anesthesiology and Washington University Pain Center, Washington University School of Medicine, St Louis, MO, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"John 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