Single hormone or synthetic agonist induces Gs/Gi coupling selectivity of EP receptors via distinct binding modes and propagating paths

Structural basis for ligand recognition and activation of the prostanoid receptors

Prostaglandin F2α (PGF2α) and thromboxane A2 (TXA2) are endogenous arachidonic acid metabolites, modulating diverse physiological processes including inflammation and cardiovascular homeostasis through activating PGF2α receptor (FP) and TXA2 receptor (TP). Ligands targeting FP and TP have demonstrated efficacy in treating conditions like glaucoma and cardiovascular diseases in humans, as well as reproductive-related diseases in animals. Here, we present five cryoelectron microscopy structures illustrating FP and TP in complex with Gq and bound to PGF2α (endogenous ligand), latanoprost acid (a clinical drug), and two other synthetic agonists. Combined with mutational and functional studies, these structures reveal not only structural features for the specific recognition of endogenous ligands and attainment of receptor selectivity of FP and TP but also the common mechanisms of receptor activation and Gq protein coupling. The findings may enrich our knowledge of ligand recognition and signal transduction of the prostanoid receptor family and facilitate rational ligand design toward these two receptors.

Molecular recognition and activation of the prostacyclin receptor by anti-pulmonary arterial hypertension drugs

The prostacyclin (PGI2) receptor (IP) is a Gs-coupled receptor associated with blood pressure regulation, allergy, and inflammatory response. It is a main therapeutic target for pulmonary arterial hypertension (PAH) and several other diseases. Here we report cryo-electron microscopy (cryo-EM) structures of the human IP-Gs complex bound with two anti-PAH drugs, treprostinil and MRE-269 (active form of selexipag), at global resolutions of 2.56 and 2.41 angstrom, respectively. These structures revealed distinct features governing IP ligand binding, receptor activation, and G protein coupling. Moreover, comparison of the activated IP structures uncovered the mechanism and key residues that determine the superior selectivity of MRE-269 over treprostinil. Combined with molecular docking and functional studies, our structures provide insight into agonist selectivity, ligand recognition, receptor activation, and G protein coupling. Our results provide a structural template for further improving IP-targeting drugs to reduce off-target activation of prostanoid receptors and adverse effects.

Structure, function and drug discovery of GPCR signaling

G protein-coupled receptors (GPCRs) are versatile and vital proteins involved in a wide array of physiological processes and responses, such as sensory perception (e.g., vision, taste, and smell), immune response, hormone regulation, and neurotransmission. Their diverse and essential roles in the body make them a significant focus for pharmaceutical research and drug development. Currently, approximately 35% of marketed drugs directly target GPCRs, underscoring their prominence as therapeutic targets. Recent advances in structural biology have substantially deepened our understanding of GPCR activation mechanisms and interactions with G-protein and arrestin signaling pathways. This review offers an in-depth exploration of both traditional and recent methods in GPCR structure analysis. It presents structure-based insights into ligand recognition and receptor activation mechanisms and delves deeper into the mechanisms of canonical and noncanonical signaling pathways downstream of GPCRs. Furthermore, it highlights recent advancements in GPCR-related drug discovery and development. Particular emphasis is placed on GPCR selective drugs, allosteric and biased signaling, polyphamarcology, and antibody drugs. Our goal is to provide researchers with a thorough and updated understanding of GPCR structure determination, signaling pathway investigation, and drug development. This foundation aims to propel forward-thinking therapeutic approaches that target GPCRs, drawing upon the latest insights into GPCR ligand selectivity, activation, and biased signaling mechanisms.