Dopamine is a neurotransmitter that has been implicated in processes as diverse as reward, addiction, control of coordinated movement, metabolism and hormonal secretion. Correspondingly, ...dysregulation of the dopaminergic system has been implicated in diseases such as schizophrenia, Parkinson's disease, depression, attention deficit hyperactivity disorder, and nausea and vomiting. The actions of dopamine are mediated by a family of five G-protein-coupled receptors. The D2 dopamine receptor (DRD2) is the primary target for both typical and atypical antipsychotic drugs, and for drugs used to treat Parkinson's disease. Unfortunately, many drugs that target DRD2 cause serious and potentially life-threatening side effects due to promiscuous activities against related receptors. Accordingly, a molecular understanding of the structure and function of DRD2 could provide a template for the design of safer and more effective medications. Here we report the crystal structure of DRD2 in complex with the widely prescribed atypical antipsychotic drug risperidone. The DRD2-risperidone structure reveals an unexpected mode of antipsychotic drug binding to dopamine receptors, and highlights structural determinants that are essential for the actions of risperidone and related drugs at DRD2.
Hallucinogens like lysergic acid diethylamide (LSD), psilocybin, and substituted N-benzyl phenylalkylamines are widely used recreationally with psilocybin being considered as a therapeutic for many ...neuropsychiatric disorders including depression, anxiety, and substance abuse. How psychedelics mediate their actions—both therapeutic and hallucinogenic—are not understood, although activation of the 5-HT2A serotonin receptor (HTR2A) is key. To gain molecular insights into psychedelic actions, we determined the active-state structure of HTR2A bound to 25-CN-NBOH—a prototypical hallucinogen—in complex with an engineered Gαq heterotrimer by cryoelectron microscopy (cryo-EM). We also obtained the X-ray crystal structures of HTR2A complexed with the arrestin-biased ligand LSD or the inverse agonist methiothepin. Comparisons of these structures reveal determinants responsible for HTR2A-Gαq protein interactions as well as the conformational rearrangements involved in active-state transitions. Given the potential therapeutic actions of hallucinogens, these findings could accelerate the discovery of more selective drugs for the treatment of a variety of neuropsychiatric disorders.
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•Cryo-EM 5-HT2A serotonin receptor structure complexed with hallucinogen and Gαq•The hallucinogen 25CN-NBOH displaces “toggle switch” tryptophan•Interactions essential for Gαq-specific signaling identified•X-ray crystal structure of LSD complexed with 5-HT2A elucidated
Roth et al. reveal structurally how psychedelics, including LSD, psilocin, mescaline, and various N-BOH analogs, mediate their therapeutic and hallucinogenic effects by binding to and activating their molecular target, the serotonin (5-HT) 2A receptor coupled with G-protein Gαq.
Neurological disorders significantly outnumber diseases in other therapeutic areas. However, developing drugs for central nervous system (CNS) disorders remains the most challenging area in drug ...discovery, accompanied with the long timelines and high attrition rates. With the rapid growth of biomedical data enabled by advanced experimental technologies, artificial intelligence (AI) and machine learning (ML) have emerged as an indispensable tool to draw meaningful insights and improve decision making in drug discovery. Thanks to the advancements in AI and ML algorithms, now the AI/ML‐driven solutions have an unprecedented potential to accelerate the process of CNS drug discovery with better success rate. In this review, we comprehensively summarize AI/ML‐powered pharmaceutical discovery efforts and their implementations in the CNS area. After introducing the AI/ML models as well as the conceptualization and data preparation, we outline the applications of AI/ML technologies to several key procedures in drug discovery, including target identification, compound screening, hit/lead generation and optimization, drug response and synergy prediction, de novo drug design, and drug repurposing. We review the current state‐of‐the‐art of AI/ML‐guided CNS drug discovery, focusing on blood–brain barrier permeability prediction and implementation into therapeutic discovery for neurological diseases. Finally, we discuss the major challenges and limitations of current approaches and possible future directions that may provide resolutions to these difficulties.
Free-moving conductive particles may affect the dielectric reliability of gas-insulated systems, e.g., gas-insulated lines (GIL) or gas-insulated switchgear (GIS). This paper reports on ...investigations on the behavior of free-moving particles under AC electric field, using different insulating gas mixtures. Multiple particles were positioned inside a GIL test setup with each particle placed within the same distance to a particle trap. To ensure reproducible and realistic particle geometry, cuboid particles were used. In this paper, a width correction factor was empirically determined for a well-known formula from the literature, which is used to calculate the lifting field strength for cuboid particles. While increasing the applied voltage, the movement of the particles was observed with a camera and further evaluated using ultra-high frequency (UHF) partial discharge (PD) measurements. The UHF phase-resolved partial discharge (PRPD) patterns of steel and aluminum particles in SF 6 , as well as in different alternative insulating gas mixtures, are compared and discussed. To determine the effectiveness of particle traps for different gas mixtures, further parameters are evaluated, such as the duration of each particle's movement and the number of particles reaching the inner conductor.
The κ-opioid receptor (KOP) mediates the actions of opioids with hallucinogenic, dysphoric, and analgesic activities. The design of KOP analgesics devoid of hallucinatory and dysphoric effects has ...been hindered by an incomplete structural and mechanistic understanding of KOP agonist actions. Here, we provide a crystal structure of human KOP in complex with the potent epoxymorphinan opioid agonist MP1104 and an active-state-stabilizing nanobody. Comparisons between inactive- and active-state opioid receptor structures reveal substantial conformational changes in the binding pocket and intracellular and extracellular regions. Extensive structural analysis and experimental validation illuminate key residues that propagate larger-scale structural rearrangements and transducer binding that, collectively, elucidate the structural determinants of KOP pharmacology, function, and biased signaling. These molecular insights promise to accelerate the structure-guided design of safer and more effective κ-opioid receptor therapeutics.
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•κ-opioid receptor active-state crystal structure disclosed•κ-opioid receptor structure reveals features involved in biased signaling•Structure provides template for the creation of safe and effective analgesics
A crystal structure of the active κ-opioid receptor provides a guide for the development of safe and effective new analgesics.
The prototypical hallucinogen LSD acts via serotonin receptors, and here we describe the crystal structure of LSD in complex with the human serotonin receptor 5-HT2B. The complex reveals ...conformational rearrangements to accommodate LSD, providing a structural explanation for the conformational selectivity of LSD’s key diethylamide moiety. LSD dissociates exceptionally slow from both 5-HT2BR and 5-HT2AR—a major target for its psychoactivity. Molecular dynamics (MD) simulations suggest that LSD’s slow binding kinetics may be due to a “lid” formed by extracellular loop 2 (EL2) at the entrance to the binding pocket. A mutation predicted to increase the mobility of this lid greatly accelerates LSD’s binding kinetics and selectively dampens LSD-mediated β-arrestin2 recruitment. This study thus reveals an unexpected binding mode of LSD; illuminates key features of its kinetics, stereochemistry, and signaling; and provides a molecular explanation for LSD’s actions at human serotonin receptors.
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•Crystal structure of the human 5-HT2B receptor bound to LSD is determined•LSD shows unexpected binding configuration in the orthosteric site•LSD has extremely slow on and off rate at 5-HT2B and 5-HT2A receptors•Accelerated LSD kinetics selectively reduce arrestin signaling at 5-HT2B and 5-HT2A
The structure of LSD with a serotonin receptor reveals the basis for its long-lasting effects and suggests ways to selectively alter receptor signaling.
Drugs active at G protein–coupled receptors (GPCRs) can differentially modulate either canonical or noncanonical signaling pathways via a phenomenon known as functional selectivity or biased ...signaling. We report biochemical studies showing that the hallucinogen lysergic acid diethylamide, its precursor ergotamine (ERG), and related ergolines display strong functional selectivity for β-arrestin signaling at the 5-HT 2B 5-hydroxytryptamine (5-HT) receptor, whereas they are relatively unbiased at the 5-HT 1B receptor. To investigate the structural basis for biased signaling, we determined the crystal structure of the human 5-HT 2B receptor bound to ERG and compared it with the 5-HT 1B /ERG structure. Given the relatively poor understanding of GPCR structure and function to date, insight into different GPCR signaling pathways is important to better understand both adverse and favorable therapeutic activities.
Binding of the glucagon peptide to the glucagon receptor (GCGR) triggers the release of glucose from the liver during fasting; thus GCGR plays an important role in glucose homeostasis. Here we report ...the crystal structure of the seven transmembrane helical domain of human GCGR at 3.4 Å resolution, complemented by extensive site-specific mutagenesis, and a hybrid model of glucagon bound to GCGR to understand the molecular recognition of the receptor for its native ligand. Beyond the shared seven transmembrane fold, the GCGR transmembrane domain deviates from class A G-protein-coupled receptors with a large ligand-binding pocket and the first transmembrane helix having a 'stalk' region that extends three alpha-helical turns above the plane of the membrane. The stalk positions the extracellular domain (~12 kilodaltons) relative to the membrane to form the glucagon-binding site that captures the peptide and facilitates the insertion of glucagon's amino terminus into the seven transmembrane domain.
Recent studies show that GPCRs rapidly interconvert between multiple states although our ability to interrogate, monitor and visualize them is limited by a relative lack of suitable tools. We ...previously reported two nanobodies (Nb39 and Nb6) that stabilize distinct ligand- and efficacy-delimited conformations of the kappa opioid receptor. Here, we demonstrate via X-ray crystallography a nanobody-targeted allosteric binding site by which Nb6 stabilizes a ligand-dependent inactive state. As Nb39 stabilizes an active-like state, we show how these two state-dependent nanobodies can provide real-time reporting of ligand stabilized states in cells in situ. Significantly, we demonstrate that chimeric GPCRs can be created with engineered nanobody binding sites to report ligand-stabilized states. Our results provide both insights regarding potential mechanisms for allosterically modulating KOR with nanobodies and a tool for reporting the real-time, in situ dynamic range of GPCR activity.
Serotonin or 5-hydroxytryptamine (5-HT) regulates a wide spectrum of human physiology through the 5-HT receptor family. We report the crystal structures of the human 5-HT 1B G protein–coupled ...receptor bound to the agonist antimigraine medications ergotamine and dihydroergotamine. The structures reveal similar binding modes for these ligands, which occupy the orthosteric pocket and an extended binding pocket close to the extracellular loops. The orthosteric pocket is formed by residues conserved in the 5-HT receptor family, clarifying the family-wide agonist activity of 5-HT. Compared with the structure of the 5-HT 2B receptor, the 5-HT 1B receptor displays a 3 angstrom outward shift at the extracellular end of helix V, resulting in a more open extended pocket that explains subtype selectivity. Together with docking and mutagenesis studies, these structures provide a comprehensive structural basis for understanding receptor-ligand interactions and designing subtype-selective serotonergic drugs.
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