Local GPCR density tips the balance of μ-opioid receptor trafficking

Holsey, M. D.; Bondar, A.; Geggier, P.; Dukas, G. V.; Webb, C. M.; Govindaraju, A.; Mathiasen, S.; Canals, M.; Lambert, N. A.; Asher, W. B.; Javitch, J. A.

doi:10.64898/2026.02.26.708286

bioRxiv · 10.64898/2026.02.26.708286

Local GPCR density tips the balance of μ-opioid receptor trafficking

Holsey, M. D.·Bondar, A.·Geggier, P.·Dukas, G. V.·Webb, C. M.·Govindaraju, A.·Mathiasen, S.·Canals, M.·Lambert, N. A.·Asher, W. B.·Javitch, J. A.

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Abstract

The extent to which local GPCR surface density governs engagement of downstream signaling and trafficking pathways remains unclear. Using single-particle tracking of the -opioid receptor (MOR), we show that receptor density differentially regulates G protein signaling and GRK2/3-{beta}-arrestin-dependent receptor trafficking. At low surface density, MORs activate G proteins but fail to enter clathrin-coated structures despite the presence of endogenous GRK2/3 and {beta}-arrestin. Increasing MOR density, co-expressing other class A GPCRs, or elevating GRK2 or {beta}-arrestin abundance rescues agonist-induced MOR trafficking. In contrast, the class B GPCR V2R blocks MOR trafficking at both low and high MOR densities. These results support a model in which increasing class A GPCR density, despite worsening effector-to-receptor stoichiometry, promotes trafficking by forming an affinity matrix that enables reversible GRK2/3 and {beta}-arrestin interactions to be productively used by neighboring receptors in a density-dependent manner, whereas class B GPCRs sequester {beta}-arrestin and block trafficking.

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Holsey, M. D., Bondar, A., Geggier, P., Dukas, G. V., Webb, C. M., Govindaraju, A., Mathiasen, S., Canals, M., Lambert, N. A., Asher, W. B., Javitch, J. A.. 2026-02-28. Local GPCR density tips the balance of μ-opioid receptor trafficking. https://doi.org/10.64898/2026.02.26.708286

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