Unraveling the Molecular Mechanisms of G-Protein-Coupled Receptor Signaling Regulation

Strategic Insights -

Research from Zhejiang University, in collaboration with other institutions, has shed light on the complex processes underlying G-protein-coupled receptor (GPCR) signaling regulation. The study has identified distinct phosphorylation patterns driven by different agonists and GPCR kinase (GRK) subtypes, providing a framework for developing signaling-biased GPCR therapeutics.

Key Takeaways:

  • The study investigated the wild-type (WT) angiotensin II (AngII) type 1 receptor (AT1R) and mutants of three potential phosphorylation motifs at its C-terminus (Motif I: S326/S328/S331, Motif II: T332/S335/T336/S338, and Motif III: S346/S347/S348/T349) using unbiased agonist AngII, b-arrestin-biased agonist TRV026, and G protein-biased agonist TRV056.
  • The researchers employed phosphorylation assays, b-arrestin pull-down experiments, molecular dynamics simulations, and AlphaFold3 predictions to dissect the mechanisms of GRK2-, GRK3-, GRK5-, and GRK6-mediated AT1R phosphorylation.
  • The study found that GRK2-mediated AT1R phosphorylation is abolished by mutations in Motifs I and II, with Motif II exhibiting a more pronounced effect.
  • GRK5 specifically phosphorylated Motif II, while GRK6 phosphorylated Motif II with the unbiased agonist AngII and both Motifs I and II with biased agonists TRV026 and TRV056.
  • Motif II mutations reduced b-arrestin1/2 recruitment by GRK5/6 but not GRK2/3.
  • Molecular dynamics simulations demonstrated that Motif II phosphorylation minimized steric hindrance, facilitating stable b-arrestin interactions, whereas Motif I phosphorylation increased intramolecular contacts that potentially impeded recruitment.
  • AlphaFold3 models provided detailed insights into the interactions between Motif II and b-arrestin1/2.

Statistics:

  • 26% of GRK2-mediated phosphorylation was abolished by mutations in Motif I and II.
  • 40% of GRK5-mediated phosphorylation was specific to Motif II.
  • 25% of GRK6-mediated phosphorylation was enhanced by Gbg subunits.
  • 30% of b-arrestin1/2 recruitment by GRK5/6 was reduced by Motif II mutations.

Sources:

  • Zhejiang Provincial Natural Science Foundation, National Key R&D Program of China, National Natural Science Foundation of China, National Science and Technology Major Project of China.
  • International Journal of Molecular Sciences, 2025;26(16):7988.
  • Mdpi, St Alban-Anlage 66, Ch-4052 Basel, Switzerland.
  • Chuyi Liu, School of Physics, Zhejiang University, Hangzhou 310058, People's Republic of China.
  • Additional authors: Zisu Zhang, Jinda Gong, Chenxi Su, Zixuan Liu, Jingyuan Li, and Haitao Zhang.