Mechanistic insights into the versatile stoichiometry and biased signaling of the apelin receptor-arrestin complex
Yang Yue, Chanjuan Xu, Lijie Wu, Man Na, Kexin Xu, Xuan Chen, Yuxuan Song, Shun Weng, Lu Xu, Fei Li, Xi Lin, Arthur Wang, Jianfeng Liu, Fei Xu
Abstract
The apelin receptor (APJR) plays a pivotal role in regulating cardiovascular and metabolic health1,2. Understanding the mechanisms of biased agonism at APJR is crucial for drug discovery, as stimulation of the β-arrestin pathway may lead to some adverse effects3. Structural analyses of APJR-Gi complexes have clarified the structural basis of receptor dimerization and activation4,5, yet the absence of structural data on APJR-arrestin complexes has impeded a comprehensive understanding of APJR stoichiometry in the dual signaling pathways and biased agonism. Here, we present APJR-β-arrestin1 structures bound to a clinical drug analog, revealing 2:2 and 2:1 stoichiometries associated with differential β-arrestin recruitment. Through comparison of the two transducer-coupled APJR structures bound to the same ligand, we identify key residues and motifs crucial for directing biased signaling. These findings highlight APJR’s versatile stoichiometry in coupling with β-arrestin and Gi proteins, establishing a framework for understanding biased agonism and guiding the development of therapeutics. The apelin receptor regulates heart and metabolic health via G-protein and β-arrestin signaling pathways. Here, authors present receptor-β-arrestin complex structures with distinct stoichiometries that provide insight into biased signaling, guiding targeted drug design.