Researchers from ETH Zurich, the University of Stuttgart, the University of Colorado Anschutz Medical Campus, Genentech, the Paul Scherrer Institute, and Stanford University School of Medicine have investigated how human β2-adrenergic receptor–β-arrestin complexes are formed and stabilized. The study, entitled “Factors modulating the assembly of human β2-adrenergic receptor–β-arrestin complexes”, has been accepted for publication in Nature Structural & Molecular Biology.
β-arrestins are key regulators of signaling by G protein-coupled receptors (GPCRs), the largest family of cell-surface receptors in the human body. GPCRs detect a wide range of external signals, including hormones, neurotransmitters, and sensory stimuli. When a signaling molecule binds to the outside of a GPCR, the receptor undergoes a conformational change that opens an intracellular cavity within the receptor core. This cavity serves as a binding site for intracellular signaling proteins such as G proteins, initiating signaling pathways that control numerous physiological processes. For example, adrenergic receptors respond to adrenaline, helping regulate cardiovascular and respiratory functions during the body's "fight-or-flight" response.
β-arrestins fine-tune these signaling events by binding to activated GPCRs and forming receptor-arrestin complexes of distinct structural and functional properties. Previous studies have suggested that β-arrestins can engage either the activated receptor core, the phosphorylated C-terminal tail of the receptor, or both simultaneously. However, how these complexes assemble at the molecular level — and how the receptor's phosphorylation, receptor core, and surrounding membrane contribute to this process — has remained difficult to resolve.
The international team combined dynamic single-molecule force spectroscopy with molecular dynamics simulations to examine different β2-adrenergic receptor–β-arrestin2 complex states in phospholipid bilayers of distinct lipid composition. The results show that β-arrestin2 binds rapidly to the phosphorylated receptor C-tail, while engagement with the open receptor core occurs on a slower timescale. The study further highlights the important role of the membrane lipid phosphatidylinositol 4,5-bisphosphate, or PIP2, in modulating the stability and conformation of the complexes.
Kristyna Pluhackova, leader of the Independent Junior Research Group “Biological Molecular Dynamics Simulations 2.0” at the Cluster of Excellence SimTech, contributed molecular dynamics expertise to the study. Her group uses computer simulations to investigate biological processes at molecular resolution. In this work, the simulations helped connect experimental force spectroscopy data with atomistic insight into how β-arrestin2, the receptor, bound ligands, and the membrane interact.
Notably, the study also involved Wenzel Gaßner, a master’s student in Materials Science at the University of Stuttgart, who completed his master’s thesis in Pluhackova’s group. His contribution reflects the strong role of early-career researchers and simulation-based approaches in interdisciplinary molecular bioscience at SimTech.