Molecular insights into the activation mechanism of GPR156 in maintaining auditory function.

The class C orphan G-protein-coupled receptor (GPCR) GPR156, which lacks the large extracellular region, plays a pivotal role in auditory function through G. Here, we firstly demonstrate that GPR156 with high constitutive activity is essential for maintaining auditory function, and further reveal the structural basis of the sustained role of GPR156. We present the cryo-EM structures of human apo GPR156 and the GPR156-G complex, unveiling a small extracellular region formed by extracellular loop 2 (ECL2) and the N-terminus.

Structural basis of tethered agonism and G protein coupling of protease-activated receptors.

Protease-activated receptors (PARs) are a unique group within the G protein-coupled receptor superfamily, orchestrating cellular responses to extracellular proteases via enzymatic cleavage, which triggers intracellular signaling pathways. Protease-activated receptor 1 (PAR1) is a key member of this family and is recognized as a critical pharmacological target for managing thrombotic disorders. In this study, we present cryo-electron microscopy structures of PAR1 in its activated state, induced by its natural tethered agonist (TA), in complex with two distinct downstream proteins, the G and G heterotrimers, respectively.

Molecular Determinant Underlying Selective Coupling of Primary G-Protein by Class A GPCRs.

G-protein-coupled receptors (GPCRs) transmit downstream signals predominantly via G-protein pathways. However, the conformational basis of selective coupling of primary G-protein remains elusive. Histamine receptors HR and HR couple with G- or G-proteins respectively.

Conformational transitions and activation of the adhesion receptor CD97.

Adhesion G protein-coupled receptors (aGPCRs) are evolutionarily ancient receptors involved in a variety of physiological and pathophysiological processes. Modulators of aGPCR, particularly antagonists, hold therapeutic promise for diseases like cancer and immune and neurological disorders. Hindered by the inactive state structural information, our understanding of antagonist development and aGPCR activation faces challenges.

Orthosteric and allosteric modulation of human HCAR2 signaling complex.

Hydroxycarboxylic acids are crucial metabolic intermediates involved in various physiological and pathological processes, some of which are recognized by specific hydroxycarboxylic acid receptors (HCARs). HCAR2 is one such receptor, activated by endogenous β-hydroxybutyrate (3-HB) and butyrate, and is the target for Niacin. Interest in HCAR2 has been driven by its potential as a therapeutic target in cardiovascular and neuroinflammatory diseases.

Unsaturated bond recognition leads to biased signal in a fatty acid receptor.

Individual free fatty acids (FAs) play important roles in metabolic homeostasis, many through engagement with more than 40G protein-coupled receptors. Searching for receptors to sense beneficial omega-3 FAs of fish oil enabled the identification of GPR120, which is involved in a spectrum of metabolic diseases. Here, we report six cryo-electron microscopy structures of GPR120 in complex with FA hormones or TUG891 and G or G trimers.

Structure insights into selective coupling of G protein subtypes by a class B G protein-coupled receptor.

The ability to couple with multiple G protein subtypes, such as G, G, or G, by a given G protein-coupled receptor (GPCR) is critical for many physiological processes. Over the past few years, the cryo-EM structures for all 15 members of the medically important class B GPCRs, all in complex with G protein, have been determined. However, no structure of class B GPCRs with G has been solved to date, limiting our understanding of the precise mechanisms of G protein coupling selectivity.

Molecular insights into the distinct signaling duration for the peptide-induced PTH1R activation.

The parathyroid hormone type 1 receptor (PTH1R), a class B1 G protein-coupled receptor, plays critical roles in bone turnover and Ca homeostasis. Teriparatide (PTH) and Abaloparatide (ABL) are terms as long-acting and short-acting peptide, respectively, regarding their marked duration distinctions of the downstream signaling. However, the mechanistic details remain obscure.

Structural basis and molecular mechanism of biased GPBAR signaling in regulating NSCLC cell growth via YAP activity.

The G protein-coupled bile acid receptor (GPBAR) is the membrane receptor for bile acids and a driving force of the liver-bile acid-microbiota-organ axis to regulate metabolism and other pathophysiological processes. Although GPBAR is an important therapeutic target for a spectrum of metabolic and neurodegenerative diseases, its activation has also been found to be linked to carcinogenesis, leading to potential side effects. Here, via functional screening, we found that two specific GPBAR agonists, R399 and INT-777, demonstrated strikingly different regulatory effects on the growth and apoptosis of non-small cell lung cancer (NSCLC) cells both in vitro and in vivo.

GPCRs steer G and G selectivity via TM5-TM6 switches as revealed by structures of serotonin receptors.

Serotonin (or 5-hydroxytryptamine, 5-HT) is an important neurotransmitter that activates 12 different G protein-coupled receptors (GPCRs) through selective coupling of G, G or G proteins. The structural basis for G protein subtype selectivity by these GPCRs remains elusive. Here, we report the structures of the serotonin receptors 5-HT, 5-HT, and 5-HT with G, and 5-HT with G.

Structural insights into human brain-gut peptide cholecystokinin receptors.

The intestinal hormone and neuromodulator cholecystokinin (CCK) receptors CCK1R and CCK2R act as a signaling hub in brain-gut axis, mediating digestion, emotion, and memory regulation. CCK receptors exhibit distinct preferences for ligands in different posttranslational modification (PTM) states. CCK1R couples to G and G, whereas CCK2R primarily couples to G.

Molecular insights into ligand recognition and activation of chemokine receptors CCR2 and CCR3.

Chemokine receptors are a family of G-protein-coupled receptors with key roles in leukocyte migration and inflammatory responses. Here, we present cryo-electron microscopy structures of two human CC chemokine receptor-G-protein complexes: CCR2 bound to its endogenous ligand CCL2, and CCR3 in the apo state. The structure of the CCL2-CCR2-G-protein complex reveals that CCL2 inserts deeply into the extracellular half of the transmembrane domain, and forms substantial interactions with the receptor through the most N-terminal glutamine.

Molecular mechanism of agonism and inverse agonism in ghrelin receptor.

Much effort has been invested in the investigation of the structural basis of G protein-coupled receptors (GPCRs) activation. Inverse agonists, which can inhibit GPCRs with constitutive activity, are considered useful therapeutic agents, but the molecular mechanism of such ligands remains insufficiently understood. Here, we report a crystal structure of the ghrelin receptor bound to the inverse agonist PF-05190457 and a cryo-electron microscopy structure of the active ghrelin receptor-Go complex bound to the endogenous agonist ghrelin.

Identification and mechanism of G protein-biased ligands for chemokine receptor CCR1.

Biased signaling of G protein-coupled receptors describes an ability of different ligands that preferentially activate an alternative downstream signaling pathway. In this work, we identified and characterized different N-terminal truncations of endogenous chemokine CCL15 as balanced or biased agonists targeting CCR1, and presented three cryogenic-electron microscopy structures of the CCR1-G complex in the ligand-free form or bound to different CCL15 truncations with a resolution of 2.6-2.

Constitutive signal bias mediated by the human GHRHR splice variant 1.

Alternative splicing of G protein-coupled receptors has been observed, but their functions are largely unknown. Here, we report that a splice variant (SV1) of the human growth hormone-releasing hormone receptor (GHRHR) is capable of transducing biased signal. Differing only at the receptor N terminus, GHRHR predominantly activates G while SV1 selectively couples to β-arrestins.

Structures of full-length glycoprotein hormone receptor signalling complexes.

Luteinizing hormone and chorionic gonadotropin are glycoprotein hormones that are related to follicle-stimulating hormone and thyroid-stimulating hormone. Luteinizing hormone and chorionic gonadotropin are essential to human reproduction and are important therapeutic drugs. They activate the same G-protein-coupled receptor, luteinizing hormone-choriogonadotropin receptor (LHCGR), by binding to the large extracellular domain.

Structural insights into ligand recognition and activation of the melanocortin-4 receptor.

Melanocortin-4 receptor (MC4R) plays a central role in the regulation of energy homeostasis. Its high sequence similarity to other MC receptor family members, low agonist selectivity and the lack of structural information concerning MC4R-specific activation have hampered the development of MC4R-seletive therapeutics to treat obesity. Here, we report four high-resolution structures of full-length MC4R in complex with the heterotrimeric G protein stimulated by the endogenous peptide ligand α-MSH, FDA-approved drugs afamelanotide (Scenesse™) and bremelanotide (Vyleesi™), and a selective small-molecule ligand THIQ, respectively.

Structural basis of GABA receptor-G protein coupling.

G-protein-coupled receptors (GPCRs) have central roles in intercellular communication. Structural studies have revealed how GPCRs can activate G proteins. However, whether this mechanism is conserved among all classes of GPCR remains unknown.

Ligand recognition, unconventional activation, and G protein coupling of the prostaglandin E receptor EP2 subtype.

Selective modulation of the heterotrimeric G protein α S subunit-coupled prostaglandin E (PGE) receptor EP2 subtype is a promising therapeutic strategy for osteoporosis, ocular hypertension, neurodegenerative diseases, and cardiovascular disorders. Here, we report the cryo-electron microscopy structure of the EP2-G complex with its endogenous agonist PGE and two synthesized agonists, taprenepag and evatanepag (CP-533536). These structures revealed distinct features of EP2 within the EP receptor family in terms of its unconventional receptor activation and G protein coupling mechanisms, including activation in the absence of a typical W "toggle switch" and coupling to G via helix 8.

Structural insights into the lipid and ligand regulation of serotonin receptors.

Serotonin, or 5-hydroxytryptamine (5-HT), is an important neurotransmitter that activates the largest subtype family of G-protein-coupled receptors. Drugs that target 5-HT, 5-HT, 5-HT and other 5-HT receptors are used to treat numerous disorders. 5-HT receptors have high levels of basal activity and are subject to regulation by lipids, but the structural basis for the lipid regulation and basal activation of these receptors and the pan-agonism of 5-HT remains unclear.

Structural insights into the human D1 and D2 dopamine receptor signaling complexes.

The D1- and D2-dopamine receptors (D1R and D2R), which signal through G and G, respectively, represent the principal stimulatory and inhibitory dopamine receptors in the central nervous system. D1R and D2R also represent the main therapeutic targets for Parkinson's disease, schizophrenia, and many other neuropsychiatric disorders, and insight into their signaling is essential for understanding both therapeutic and side effects of dopaminergic drugs. Here, we report four cryoelectron microscopy (cryo-EM) structures of D1R-G and D2R-G signaling complexes with selective and non-selective dopamine agonists, including two currently used anti-Parkinson's disease drugs, apomorphine and bromocriptine.