The molecular associations in clathrin-coated pit regulate β-arrestinmediated MAPK signaling downstream of μ-opioid receptor

It has been thought that mu-opioid receptors (MOPs) activate the G protein-mediated analgesic pathway and beta-arrestin 2-mediated side effect pathway; however, ligands that only minimally recruit beta-arrestin 2 to MOPs may also cause opioid side effects. Moreover, such side effects have been induced in mutant mice lacking beta-arrestin 2 or expressing phosphorylation-deficient MOPs that do not recruit beta-arrestin 2. These findings raise the critical question of whether beta-arrestin 2 recruitment to MOP triggers side effects. Here, we show that beta-arrestin 1 and 2 are essential in the efficient activation of the Gi/o-mediated MAPK signaling at MOP. Moreover, the magnitude of beta-arrestin-mediated signals is not correlated with the magnitude of phosphorylation of the carboxyl-terminal of MOP, which is used to evaluate the beta-arrestin bias of a ligand. Instead, the molecular association with beta 2-adaptin and clathrin heavy chain in the formation of clathrin-coated pits is essential for beta-arrestin to activate MAPK signaling. Our findings provide insights into G protein-coupled receptor-mediated signaling and further highlight a concept that the accumulation of molecules required for endocytosis is critical for activating intracellular signaling. (c) 2022 Elsevier Inc. All rights reserved.

Automated summary

Through the study, it is found that beta-arrestin 1 and 2 are essential for the efficient activation of Gi/o-mediated MAPK signaling at MOP. The magnitude of beta-arrestin-mediated signals is not correlated with the phosphorylation of the carboxyl-terminal of MOP, but with the molecular association with beta 2-adaptin and clathrin heavy chain in the formation of clathrin-coated pits. The findings deepen our understanding of G protein-coupled receptor-mediated signaling and highlight the critical role of the accumulation of molecules required for endocytosis in activating intracellular signaling.