Molecular mechanism of β-arrestin 2 interaction with phosphorylated intracellular loop 3 of dopamine receptor D2

G protein-coupled receptors (GPCRs) are essential signaling molecules involved in various physiological processes, with β-arrestins playing crucial roles in receptor desensitization, internalization, and G protein-independent signaling. Although the interaction between the phosphorylated C-terminal tail (C-tails) of a GPCR and the N-domain of an arrestin has been well studied, the mechanisms underlying arrestin binding to GPCRs with short C-tails and long intracellular loop 3 (ICL3) remain unclear. We provide novel insights into the structural and functional interaction between the phosphorylated ICL3 of the dopamine receptor D2 (D2R) and β-arrestin 2 (βarr2) using hydrogen/deuterium exchange mass spectrometry (HDX-MS), and other biochemical approaches. By identifying key phosphorylated residues and elucidating distinct βarr2 conformational changes, our findings highlight novel aspects of GPCR–arrestin interaction.