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Previously identified under the single designation of Aerococcus urinae , three distinct taxonomic species have been distinguished as Aerococcus loyolae, Aerococcus mictus, and Aerococcus tenax . Here, we present the complete genome sequences of the type strains of these species assembled via a combination of short-read and long-read sequencing techniques.Registered at ClinicalTrials.gov (NCT01166438)., Competing Interests: A.J.W. discloses scientific advisory board membership for Cerillo, Pathnostics, and Urobiome Therapeutics, as well as funding from Pathnostics.

Bacterial isolates from the human urinary microbiome have been extensively studied for their antibiotic resistance; however, little work has been done on those isolates that are difficult to grow in vitro . This study was designed to qualify a serum-based medium, New York City Broth III (NYCIII), and a broth microdilution method to determine the antibiotic susceptibility of previously underreported or undescribed microbes that have a difficult time growing in standard Mueller-Hinton broth. Here, we demonstrate that NYCIII microbroth dilution can be an effective method for the determination of antibiotic susceptibility of species found in the human urinary microbiome. We show that this method serves well to characterize fastidious and anaerobic urinary microbes that have no Clinical and Laboratory Standards Institute (CLSI) guidelines, including several in the families Aerococcaceae , Lactobacillaceae , or Actinomycetaceae . Previous studies using expanded quantitative urine culture reveal that urine samples from clinical patients are commonly polymicrobial in composition. Thus, we test whether NYCIII can serve as a viable harmonized medium, capable of supporting antibiotic susceptibility testing in a range of fastidious, non-fastidious, and anaerobic urinary microbes. We propose this methodology to be standardized comparable to CLSI standards to allow for resistance testing in uncharacterized urinary bacteria., Importance: Antibiotic susceptibilities of fastidious and anaerobic bacteria of the human urinary microbiome are largely underreported due to difficulty in growing them in the lab environment. The current standard medium, Muller-Hinton broth, has difficulty supporting the growth of many of these species, leaving microbiologists without a standardized method. To address this need, this study offers a methodology to survey susceptibilities in a high-throughput manner of these understudied microbes with a proposed harmonized medium, NYCIII, which is capable of supporting the growth of both fastidious and non-fastidious urinary microbes. Broader standardization of this method can allow for the development of antibiotic-resistant breakpoints of the many uncharacterized urinary microbes., Competing Interests: A.J.W. declares membership on the advisory boards of Pathnostics and Urobiome Therapeutics, and funding from Pathnostics. The other authors declare no conflicts of interest.

Biallelic loss of SPG11 function constitutes the most frequent cause of complicated autosomal recessive hereditary spastic paraplegia (HSP) with thin corpus callosum, resulting in progressive multisystem neurodegeneration. While the impact of neuroinflammation is an emerging and potentially treatable aspect in neurodegenerative diseases and leukodystrophies, the role of immune cells in SPG11-HSP patients is unknown. Here, we performed a comprehensive immunological characterization of SPG11-HSP, including examination of three human postmortem brain donations, immunophenotyping of patients' peripheral blood cells and patient-specific induced pluripotent stem cell-derived microglia-like cells (iMGL). We delineate a previously unknown role of innate immunity in SPG11-HSP. Neuropathological analysis of SPG11-HSP patient brain tissue revealed profound microgliosis in areas of neurodegeneration, downregulation of homeostatic microglial markers and cell-intrinsic accumulation of lipids and lipofuscin in IBA1 + cells. In a larger cohort of SPG11-HSP patients, the ratio of peripheral classical and intermediate monocytes was increased, along with increased serum levels of IL-6 that correlated with disease severity. Stimulation of patient-specific iMGLs with IFNγ led to increased phagocytic activity compared to control iMGL as well as increased upregulation and release of proinflammatory cytokines and chemokines, such as CXCL10. On a molecular basis, we identified increased STAT1 phosphorylation as mechanism connecting IFNγ-mediated immune hyperactivation and SPG11 loss of function. STAT1 expression was increased both in human postmortem brain tissue and in an Spg11 -/- mouse model. Application of an STAT1 inhibitor decreased CXCL10 production in SPG11 iMGL and rescued their toxic effect on SPG11 neurons. Our data establish neuroinflammation as a novel disease mechanism in SPG11-HSP patients and constitute the first description of myeloid cell/ microglia activation in human SPG11-HSP. IFNγ/ STAT1-mediated neurotoxic effects of hyperreactive microglia upon SPG11 loss of function indicate that immunomodulation strategies may slow down disease progression., (© 2024. The Author(s).)

For an effective drug, strong binding to the target protein is a prerequisite, but it is not enough. To produce a particular functional response, drugs need to either block the proteins' functions or modulate their activities by changing their conformational equilibrium. The binding free energy of a compound to its target is routinely calculated, but the timescales for the protein conformational changes are prohibitively long to be efficiently modeled via physics-based simulations. Thermodynamic principles suggest that the binding free energies of the ligands with different receptor conformations may infer their efficacy. However, this hypothesis has not been thoroughly validated. We present an actionable protocol and a comprehensive study to show that binding thermodynamics provides a strong predictor of the efficacy of a ligand. We apply the absolute binding free energy perturbation method to ligands bound to active and inactive states of eight G protein-coupled receptors and a nuclear receptor and then compare the resulting binding free energies. We find that carefully designed restraints are often necessary to efficiently model the corresponding conformational ensembles for each state. Our method achieves unprecedented performance in classifying ligands as agonists or antagonists across the various investigated receptors, all of which are important drug targets.

G protein-coupled receptors (GPCRs) within the same subfamily often share high homology in their orthosteric pocket and therefore pose challenges to drug development. The amino acids that form the orthosteric binding pocket for epinephrine and norepinephrine in the β 1 and β 2 adrenergic receptors (β 1 AR and β 2 AR) are identical. Here, to examine the effect of conformational restriction on ligand binding kinetics, we synthesized a constrained form of epinephrine. Surprisingly, the constrained epinephrine exhibits over 100-fold selectivity for the β 2 AR over the β 1 AR. We provide evidence that the selectivity may be due to reduced ligand flexibility that enhances the association rate for the β 2 AR, as well as a less stable binding pocket for constrained epinephrine in the β 1 AR. The differences in the amino acid sequence of the extracellular vestibule of the β 1 AR allosterically alter the shape and stability of the binding pocket, resulting in a marked difference in affinity compared to the β 2 AR. These studies suggest that for receptors containing identical binding pocket residues, the binding selectivity may be influenced in an allosteric manner by surrounding residues, like those of the extracellular loops (ECLs) that form the vestibule. Exploiting these allosteric influences may facilitate the development of more subtype-selective ligands for GPCRs., (© 2023. The Author(s).)

The μ-opioid receptor (μOR) is the major target for opioid analgesics. Activation of μOR initiates signaling through G protein pathways as well as through β-arrestin recruitment. μOR agonists that are biased towards G protein signaling pathways demonstrate diminished side effects. PZM21, discovered by computational docking, is a G protein biased μOR agonist. Here we report the cryoEM structure of PZM21 bound μOR in complex with G i protein. Structure-based evolution led to multiple PZM21 analogs with more pronounced G i protein bias and increased lipophilicity to improve CNS penetration. Among them, FH210 shows extremely low potency and efficacy for arrestin recruitment. We further determined the cryoEM structure of FH210 bound to μOR in complex with G i protein and confirmed its expected binding pose. The structural and pharmacological studies reveal a potential mechanism to reduce β-arrestin recruitment by the μOR, and hold promise for developing next-generation analgesics with fewer adverse effects., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Current protocols converting human induced pluripotent stem cells (iPSCs) into induced microglia-like cells (iMGL) are either dependent on overexpression of transcription factors or require substantial experience in stem-cell technologies. Here, we developed an easy-to-use two-step protocol to convert iPSCs into functional iMGL via: (1) highly efficient differentiation of hematopoietic progenitor cells (HPCs) from iPSCs, and (2) optimized maturation of HPCs to iMGL. A sequential harvesting approach led to an increased HPC yield. The protocol implemented a freezing step, thus allowing HPC biobanking and flexible timing of differentiation into iMGL. Our iMGL responded adequately to the inflammatory stimuli LPS, and iMGL RNAseq analysis matched those of other frequently used protocols. Comparing three different coating modalities, we increased the iMGL yield by culturing on uncoated glass surfaces, thereby retaining differentiation efficiency and functional hallmarks of iMGL. In summary, we provide a high-quality, easy-to-use protocol, rendering generation and functional studies on iMGL an accessible lab resource.

Pathogenic bi-allelic variants in the SPG11 gene result in rare motor neuron disorders such as Hereditary Spastic Paraplegia type 11, Charcot-Marie Tooth, and Juvenile Amyotrophic Lateral Sclerosis-5. The main challenge in SPG11-linked disease research is the lack of antibodies against SPG11 encoded spatacsin. Here, we describe the CRISPR/Cas9 mediated generation and validation of an endogenously tagged SPG11- human iPSC line that contains an HA tag at the C-terminus of SPG11. The line exhibits multi-lineage differentiation potential and holds promise for studying the role of spatacsin and for the elucidation of SPG11-associated pathogenesis. Resource Table., (Copyright © 2021 The Author(s). Published by Elsevier B.V. All rights reserved.)

Beta adrenergic receptors (βARs) mediate physiologic responses to the catecholamines epinephrine and norepinephrine released by the sympathetic nervous system. While the hormone epinephrine binds β 1 AR and β 2 AR with similar affinity, the smaller neurotransmitter norepinephrine is approximately tenfold selective for the β 1 AR. To understand the structural basis for this physiologically important selectivity, we solved the crystal structures of the human β 1 AR bound to an antagonist carazolol and different agonists including norepinephrine, epinephrine and BI-167107. Structural comparison revealed that the catecholamine-binding pockets are identical between β 1 AR and β 2 AR, but the extracellular vestibules have different shapes and electrostatic properties. Metadynamics simulations and mutagenesis studies revealed that these differences influence the path norepinephrine takes to the orthosteric pocket and contribute to the different association rates and thus different affinities.

Background: The therapeutic effects of antipsychotic drugs (APDs) are mainly attributed to their postsynaptic inhibitory functions on the dopamine D2 receptor, which, however, cannot explain the delayed onset of full therapeutic efficacy. It was previously shown that APDs accumulate in presynaptic vesicles during chronic treatment and are released like neurotransmitters in an activity-dependent manner triggering an auto-inhibitory feedback mechanism. Although closely mirroring therapeutic action onset, the functional consequence of the APD accumulation process remained unclear., Aims: Here we tested whether the accumulation of the APD haloperidol (HAL) is required for full therapeutic action in psychotic-like rats., Methods: We designed a HAL analog compound (HAL-F), which lacks the accumulation property of HAL, but retains its postsynaptic inhibitory action on dopamine D2 receptors., Results/outcomes: By perfusing LysoTracker fluorophore-stained cultured hippocampal neurons, we confirmed the accumulation of HAL and the non-accumulation of HAL-F. In an amphetamine hypersensitization psychosis-like model in rats, we found that subchronic intracerebroventricularly delivered HAL (0.1 mg/kg/day), but not HAL-F (0.3-1.5 mg/kg/day), attenuates psychotic-like behavior in rats., Conclusions/interpretation: These findings suggest the presynaptic accumulation of HAL may serve as an essential prerequisite for its full antipsychotic action and may explain the time course of APD action. Targeting accumulation properties of APDs may, thus, become a new strategy to improve APD action.

Most drugs acting on G-protein-coupled receptors target the orthosteric binding pocket where the native hormone or neurotransmitter binds. There is much interest in finding allosteric ligands for these targets because they modulate physiologic signaling and promise to be more selective than orthosteric ligands. Here we describe a newly developed allosteric modulator of the β 2 -adrenergic receptor (β 2 AR), AS408, that binds to the membrane-facing surface of transmembrane segments 3 and 5, as revealed by X-ray crystallography. AS408 disrupts a water-mediated polar network involving E122 3.41 and the backbone carbonyls of V206 5.45 and S207 5.46 . The AS408 binding site is adjacent to a previously identified molecular switch for β 2 AR activation formed by I 3.40 , P 5.50 and F 6.44 . The structure reveals how AS408 stabilizes the inactive conformation of this switch, thereby acting as a negative allosteric modulator for agonists and positive allosteric modulator for inverse agonists.

Proteinase-activated receptor 2 (PAR2) is a class A G protein-coupled receptor whose activation has been associated with inflammatory diseases and cancer, thus representing a valuable therapeutic target. Pathophysiological roles of PAR2 are often characterized using peptidic PAR2 agonists. Peptidic ligands are frequently unstable in vivo and show poor bioavailability, and only a few approaches toward drug-like nonpeptidic PAR2 ligands have been described. The herein-described ligand 5a (IK187) is a nonpeptidic PAR2 agonist with submicromolar potency in a functional assay reflecting G protein activation. The ligand also showed substantial β-arrestin recruitment. The development of the compound was guided by the crystal structure of PAR2, when the C-terminal end of peptidic agonists was replaced by a small molecule based on a disubstituted phenylene scaffold. IK187 shows preferable metabolic stability and may serve as a lead compound for the development of nonpeptidic drugs addressing PAR2., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

The α 2 adrenergic receptors (α 2 ARs) are G protein-coupled receptors (GPCRs) that respond to adrenaline and noradrenaline and couple to the Gi/o family of G proteins. α 2 ARs play important roles in regulating the sympathetic nervous system. Dexmedetomidine is a highly selective α 2 AR agonist used in post-operative patients as an anxiety-reducing, sedative medicine that decreases the requirement for opioids. As is typical for selective αAR agonists, dexmedetomidine consists of an imidazole ring and a substituted benzene moiety lacking polar groups, which is in contrast to βAR-selective agonists, which share an ethanolamine group and an aromatic system with polar, hydrogen-bonding substituents. To better understand the structural basis for the selectivity and efficacy of adrenergic agonists, we determined the structure of the α 2B AR in complex with dexmedetomidine and Go at a resolution of 2.9 Å by single-particle cryo-EM. The structure reveals the mechanism of α 2 AR-selective activation and provides insights into Gi/o coupling specificity.

Muscarinic M 3 receptor antagonists and inverse agonists displaying high affinity and subtype selectivity over the antitarget M 2 are valuable pharmacological tools and may enable improved treatment of chronic obstructive pulmonary disease (COPD), asthma, or urinary incontinence. On the basis of known M 3 antagonists comprising a piperidine or quinuclidine unit attached to a biphenyl carbamate, 5-fluoro substitution was responsible for M 3 subtype selectivity over M 2 , while 3'-chloro substitution substantially increased affinity through a σ-hole interaction. Resultantly, two piperidinyl- and two quinuclidinium-substituted biphenyl carbamates OFH243 ( 13n ), OFH244 ( 13m ), OFH3911 ( 14n ), and OFH3912 ( 14m ) were discovered, which display two-digit picomolar affinities with K i values from 0.069 to 0.084 nM, as well as high selectivity over the M 2 subtype (46- to 68-fold). While weak inverse agonistic properties were determined for the biphenyl carbamates 13m and 13n , neutral antagonism was observed for 14m and 14n and tiotropium under identical assay conditions.

Parkinson's disease (PD) is the most frequently occurring movement disorder, with an increasing incidence due to an aging population. For many years, the post-mortem brain was regarded as the gold standard for the analysis of the human pathology of this disease. However, modern stem cell technologies, including the analysis of patient-specific neurons and glial cells, have opened up new avenues for dissecting the pathologic mechanisms of PD. Most data on morphological changes, such as cell death or changes in neurite complexity, or functional deficits were acquired in 2D and few in 3D models. This review will examine the prerequisites for human disease modeling in PD, covering the generation of midbrain neurons, 3D organoid midbrain models, the selection of controls including genetically engineered lines, and the study of cell-cell interactions. We will present major disease phenotypes in human in vitro models of PD, focusing on those phenotypes that have been detected in genetic and sporadic PD models. An additional point covered in this review will be the use of induced pluripotent stem cell (iPSC)-derived technologies to model cell-cell interactions in PD., (Copyright © 2020 Simmnacher, Lanfer, Rizo, Kaindl and Winner.)

Histamine H 4 receptor (H 4 R) orthologues are G-protein-coupled receptors (GPCRs) that exhibit species-dependent basal activity. In contrast to the basally inactive mouse H 4 R (mH 4 R), human H 4 R (hH 4 R) shows a high degree of basal activity. We have performed long-timescale molecular dynamics simulations and rigidity analyses on wild-type hH 4 R, the experimentally characterized hH 4 R variants S179M, F169V, F169V+S179M, F168A, and on mH 4 R to investigate the molecular nature of the differential basal activity. H 4 R variant-dependent differences between essential motifs of GPCR activation and structural stabilities correlate with experimentally determined basal activities and provide a molecular explanation for the differences in basal activation. Strikingly, during the MD simulations, F169 45.55 dips into the orthosteric binding pocket only in the case of hH 4 R, thus adopting the role of an agonist and contributing to the stabilization of the active state. The results shed new light on the molecular mechanism of basal H 4 R activation that are of importance for other GPCRs., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The M2 muscarinic acetylcholine receptor (M2R) is a prototypical GPCR that plays important roles in regulating heart rate and CNS functions. Crystal structures provide snapshots of the M2R in inactive and active states, but the allosteric link between the ligand binding pocket and cytoplasmic surface remains poorly understood. Here we used solution NMR to examine the structure and dynamics of the M2R labeled with 13 CH 3 -ε-methionine upon binding to various orthosteric and allosteric ligands having a range of efficacy for both G protein activation and arrestin recruitment. We observed ligand-specific changes in the NMR spectra of 13 CH 3 -ε-methionine probes in the M2R extracellular domain, transmembrane core, and cytoplasmic surface, allowing us to correlate ligand structure with changes in receptor structure and dynamics. We show that the M2R has a complex energy landscape in which ligands with different efficacy profiles stabilize distinct receptor conformations., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Human induced pluripotent stem cells (hiPSCs) are an important tool for research and regenerative medicine, but their efficient cryopreservation remains a major challenge. The current gold standard is slow-rate freezing of dissociated colonies in suspension, but low recovery rates limit immediate post-thawing applicability. We tested whether ultrafast cooling by adherent vitrification improves post-thawing survival in a selection of hiPSCs and small molecule neural precursor cells (smNPCs) from Parkinson's disease and controls. In a dual-center study, we compared the results by immunocytochemistry (ICC), fluorescence-activated cell sorting analysis, and RNA-sequencing (RNA-seq). Adherent vitrification was achieved in the so-called TWIST substrate, a device combining cultivation, vitrification, storage, and post-thawing cultivation. Adherent vitrification resulted in preserved confluency and significantly higher cell numbers, and viability at day 1 after thawing, while results were not significantly different at day 4 after thawing. RNA-seq and ICC of hiPSCs revealed no change in gene expression and pluripotency markers, indicating that physical damage of slow-rate freezing disrupts cellular membranes. Scanning electron microscopy showed preserved colony integrity by adherent vitrification. Experiments using smNPCs demonstrated that adherent vitrification is also applicable to neural derivatives of hiPSCs. Our data suggest that, compared to the state-of-the-art slow-rate freezing in suspension, adherent vitrification is an improved cryopreservation technique for hiPSCs and derivatives. Stem Cells Translational Medicine 2019;8:247&259., (© 2018 The Authors Stem Cells Translational Medicine published by Wiley Periodicals, Inc. on behalf of AlphaMed Press.)

Human pluripotent stem (PS) cells are a relevant platform to model human-specific neurological disorders. In this chapter, we focus on human stem cell models for neuropsychiatric disorders including induced pluripotent stem (iPS) cell-derived neural precursor cells (NPCs), neurons and cerebral organoids. We discuss crucial steps for planning human disease modeling experiments. We introduce the different strategies of human disease modeling including transdifferentiation, human embryonic stem (ES) cell-based models, iPS cell-based models and genome editing options. Analysis of disease-relevant phenotypes is discussed. In more detail, we provide exemplary insight into modeling of the neurodevelopmental defects in autism spectrum disorder (ASD) and the process of neurodegeneration in Alzheimer's disease (AD). Besides monogenic diseases, iPS cell-derived models also generated data from idiopathic and sporadic cases.

Drugs that treat chronic obstructive pulmonary disease by antagonizing the M3 muscarinic acetylcholine receptor (M3R) have had a significant effect on health, but can suffer from their lack of selectivity against the M2R subtype, which modulates heart rate. Beginning with the crystal structures of M2R and M3R, we exploited a single amino acid difference in their orthosteric binding pockets using molecular docking and structure-based design. The resulting M3R antagonists had up to 100-fold selectivity over M2R in affinity and over 1,000-fold selectivity in vivo. The crystal structure of the M3R-selective antagonist in complex with M3R corresponded closely to the docking-predicted geometry, providing a template for further optimization., Competing Interests: Conflict of interest statement: B.K.K. is a cofounder of and consultant for ConfometRx, Inc., (Copyright © 2018 the Author(s). Published by PNAS.)

Introduction: One characteristic of Alzheimer's disease is the formation of amyloid-β plaques, which are typically linked to neuroinflammation and surrounded by inflammatory cells such as microglia and infiltrating immune cells., Methods: Here, we describe nonneurogenic doublecortin (DCX) positive cells, DCX being generally used as a marker for young immature neurons, at sites of amyloid-β plaques in various transgenic amyloid mouse models and in human brains with plaque pathology., Results: The plaque-associated DCX+ cells were not of neurogenic identity, instead most of them showed coexpression with markers for microglia (ionized calcium-binding adapter molecule 1) and for phagocytosis (CD68 and TREM2). Another subpopulation of plaque-associated DCX+ cells was negative for ionized calcium-binding adapter molecule 1 but was highly positive for the pan-leukocyte marker CD45. These hematopoietic cells were identified as CD3-and CD8-positive and CD4-negative T-cells., Discussion: Peculiarly, the DCX+/ionized calcium-binding adapter molecule 1+ microglia and DCX+/CD8+ T-cells were closely attached, suggesting that these two cell types are tightly interacting and that this interaction might shape plaque pathology., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

The dopamine D 2 receptor (D 2 R) is a common drug target for the treatment of a variety of neurological disorders including schizophrenia. Structure based design of subtype selective D 2 R antagonists requires high resolution crystal structures of the receptor and pharmacological tools promoting a better understanding of the protein-ligand interactions. Recently, we reported the development of a chemically activated dopamine derivative (FAUC150) designed to covalently bind the L94C mutant of the dopamine D 2 receptor. Using FAUC150 as a template, we elaborated the design and synthesis of irreversible analogs of the potent antipsychotic drug haloperidol forming covalent D 2 R-ligand complexes. The disulfide- and Michael acceptor-functionalized compounds showed significant receptor affinity and an irreversible binding profile in radioligand depletion experiments., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The chemokine receptor CXCR3 is a G protein-coupled receptor that conveys extracellular signals into cells by changing its conformation upon ligand binding. We previously hypothesized that small-molecule allosteric CXCR3-agonists do not bind to the same allosteric binding pocket as 8-azaquinazolinone-based negative allosteric modulators. We have now performed molecular-dynamics (MD) simulations with metadynamics enhanced sampling on the CXCR3 system to refine structures and binding modes and to predict the CXCR3-binding affinities of the biased allosteric agonist FAUC1036 and the negative allosteric modulator RAMX3. We have identified two distinct binding sites; a "shallow" and a second "deeper" pocket to which the biased allosteric agonist FAUC1036 and negative allosteric modulator RAMX3 bind, respectively., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Crystal structures of G protein-coupled receptor (GPCR) ligand complexes allow a rational design of novel molecular probes and drugs. Here we report the structure-guided design, chemical synthesis and biological investigations of bivalent ligands for dopamine D2 receptor/neurotensin NTS1 receptor (D2R/NTS1R) heterodimers. The compounds of types 1-3 consist of three different D2R pharmacophores bound to an affinity-generating lipophilic appendage, a polyethylene glycol-based linker and the NTS1R agonist NT(8-13). The bivalent ligands show binding affinity in the picomolar range for cells coexpressing both GPCRs and unprecedented selectivity (up to three orders of magnitude), compared with cells that only express D2Rs. A functional switch is observed for the bivalent ligands 3b,c inhibiting cAMP formation in cells singly expressing D2Rs but stimulating cAMP accumulation in D2R/NTS1R-coexpressing cells. Moreover, the newly synthesized bivalent ligands show a strong, predominantly NTS1R-mediated β-arrestin-2 recruitment at the D2R/NTS1R-coexpressing cells.