Direct SUMOylation of M1 muscarinic acetylcholine receptor increases its ligand‐binding affinity and signal transduction

What is it about?

SUMOylation is a significant posttranslational modification by small ubiquitin-related modifier (SUMO). Increasing evidence shows SUMOylation could regulate G protein-coupled receptors (GPCRs) signaling; however, very few GPCRs were proved to be SUMOylation targets to date. Here we identified M1 muscarinic acetylcholine receptor (M1 mAChR), a member of GPCRs, as a new SUMO substrate. When the mAChRs receptors were activated by the agonist carbachol, the colocalization of M1 mAChRs and SUMO-1 proteins markedly decreased in immunoprecipitation and immunofluorescence assays. SUMOylation of M1 mAChR played an important role in increasing the ligand-binding affinity to M1 mAChR, signaling efficiencies and receptor endocytosis. Through site-directed mutagenesis approach K327 was identified as the SUMOylation site of M1 mAChR. Mutation of consensus SUMOylation site of M1 mAChRs could reduce not only the colocalization of SUMO-1, but also the ligand-binding affinity and the signaling transduction. The function of M1 mAChR was regulated by SUMOylation through the stabilization of active state conformation revealed by molecular dynamics simulations. Overall, we provide evidence that M1 SUMOylation is an important post-translational modification involved in regulation of the affinity for agonists and for activation of signaling pathways.

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