Rimota-Gd: Paramagnetic Probe for In Vivo MRI Studies of the Cannabinoid 1 Receptor Distribution in the Mouse Brain.

The cannabinoid 1 receptor (CB1) is highly expressed in the central nervous system, where its physiological functions include the regulation of energy balance, pain, and addiction. Herein, we develop and validate a technique to use magnetic resonance imaging (MRI) to investigate the distribution of CB1 across mouse brains with high spatial resolution, expanding previously described in vitro studies and in vivo studies with positron emission tomography (PET). To support the MRI investigations, we developed a ligand that is specific for in vivo neuroimaging of CB1.

Reflections from Nobel laureates in chemistry.

Since the first award in 1901, the Nobel Prize has come to signify the pinnacle of scientific achievement. In this Voices piece in the August special issue of Cell Chemical Biology entitled "Bridging chemistry and biology," we ask Nobel laureates to reflect on the impact the prize had on them. We learn how it affected their life or work, their outlook on science, the lessons learned, and their advice for the next generation of scientists.

Fluorine-19 labeling of the tryptophan residues in the G protein-coupled receptor NK1R using the 5-fluoroindole precursor in Pichia pastoris expression.

In NMR spectroscopy of biomolecular systems, the use of fluorine-19 probes benefits from a clean background and high sensitivity. Therefore, F-labeling procedures are of wide-spread interest. Here, we use 5-fluoroindole as a precursor for cost-effective residue-specific introduction of 5-fluorotryptophan (5F-Trp) into G protein-coupled receptors (GPCRs) expressed in Pichia pastoris.

F-NMR studies of the impact of different detergents and nanodiscs on the A adenosine receptor.

For the A adenosine receptor (AAR), a class A G-protein-coupled receptor (GPCR), reconstituted in n-dodecyl-β-D-maltoside (DDM)/‌‌‌‌‌cholesteryl hemisuccinate (CHS) mixed micelles, previous F-NMR studies revealed the presence of multiple simultaneously populated conformational states. Here, we study the influence of a different detergent, lauryl maltose neopentyl glycol (LMNG) in mixed micelles with CHS, and of lipid bilayer nanodiscs on these conformational equilibria. The populations of locally different substates are pronouncedly different in DDM/‌‌‌‌‌CHS and LMNG/‌‌‌‌‌CHS micelles, whereas the AAR conformational manifold in LMNG/‌‌‌‌‌CHS micelles is closely similar to that in the lipid bilayer nanodiscs.

Two-Dimensional NMR Spectroscopy of the G Protein-Coupled Receptor AAR in Lipid Nanodiscs.

Eight hundred and twenty-six human G protein-coupled receptors (GPCRs) mediate the actions of two-thirds of the human hormones and neurotransmitters and over one-third of clinically used drugs. Studying the structure and dynamics of human GPCRs in lipid bilayer environments resembling the native cell membrane milieu is of great interest as a basis for understanding structure-function relationships and thus benefits continued drug development. Here, we incorporate the human A adenosine receptor (AAR) into lipid nanodiscs, which represent a detergent-free environment for structural studies using nuclear magnetic resonance (NMR) in solution.

Selective polypeptide ligand binding to the extracellular surface of the transmembrane domains of the class B GPCRs GLP-1R and GCGR.

Crystal and cryo-EM structures of the glucagon-like peptide-1 receptor (GLP-1R) and glucagon receptor (GCGR) bound with their peptide ligands have been obtained with full-length constructs, indicating that the extracellular domain (ECD) is indispensable for specific ligand binding. This article complements these data with studies of ligand recognition of the two receptors in solution. Paramagnetic NMR relaxation enhancement measurements using dual labeling with fluorine-19 probes on the receptor and nitroxide spin labels on the peptide ligands provided new insights.

Adenosine A Receptor (AAR) Ligand Screening Using the F-NMR Probe FPPA.

The binding affinity of G protein-coupled receptor (GPCR) ligands is customarily measured by radio-ligand competition experiments. As an alternative approach, F nuclear magnetic resonance spectroscopy (F-NMR) is used for the screening of small-molecule lead compounds in drug discovery; the two methods are complementary in that the measurements are performed with widely different experimental conditions. Here, we used the structure of the A adenosine receptor (AAR) complex with (3-(4-amino-3-methylbenzyl)-7-(furan-2-yl)-3-[1,2,3]triazolo[4,5-]pyrimidin-5-amine) as the basis for the design of a fluorine-containing probe molecule, (4-(furan-2-yl)-7-(4-(trifluoromethyl)benzyl)-7-pyrrolo[2,3-]pyramidin-2-amine), for binding studies with AAR.

Solvent accessibility of a GPCR transmembrane domain probed by in-membrane chemical modification (IMCM).

G protein-coupled receptors (GPCRs) transmit signals from drugs across cell membranes, leading to associated physiological effects. To study the structural basis of the transmembrane signalling, in-membrane chemical modification (IMCM) has previously been introduced for F-labelling of GPCRs expressed in Spodoptera frugiperda (Sf9) insect cells. Here, IMCM is used with the A adenosine receptor (A AR) expressed in Pichia pastoris; F-NMR revealed nearly complete solvent protection of the A AR transmembrane domain in the membrane and in 2,2-didecylpropane-1,3-bis-β-D-maltopyranoside (LMNG)/cholesteryl hemisuccinate (CHS) micelles, and extensive solvent accessibility for A AR in n-dodecyl β-D-maltoside (DDM)/CHS micelles.

GPCR structural characterization by NMR spectroscopy in solution.

In the human proteome, 826 G-protein-coupled receptors (GPCRs) interact with extracellular stimuli to initiate cascades of intracellular signaling. Determining conformational dynamics and intermolecular interactions are key to understand GPCR function as a basis for drug design. X-ray crystallography and cryo-electron microscopy (cryo-EM) contribute molecular architectures of GPCRs and GPCR-signaling complexes.

G Protein-coupled Receptor (GPCR) Reconstitution and Labeling for Solution Nuclear Magnetic Resonance (NMR) Studies of the Structural Basis of Transmembrane Signaling.

G protein-coupled receptors (GPCRs) are a large membrane protein family found in higher organisms, including the human body. GPCRs mediate cellular responses to diverse extracellular stimuli and thus control key physiological functions, which makes them important targets for drug design. Signaling by GPCRs is related to the structure and dynamics of these proteins, which are modulated by extrinsic ligands as well as by intracellular binding partners such as G proteins and arrestins.

Dual-acting antitumor agents targeting the A adenosine receptor and histone deacetylases: Design and synthesis of 4-(furan-2-yl)-1H-pyrazolo[3,4-d]pyrimidin-6-amine derivatives.

Based on its inhibition by antagonists, the A adenosine receptor (AAR) has attracted attention as an anti-tumor drug target; however, in preclinical models and clinical trials, AAR antagonists have so far shown only limited efficacy as standalone therapies. The design of dual-acting compounds, targeting the AAR and histone deacetylases (HDACs), is used here as an approach to the discovery of novel and more potent antitumor agents. Based on the core structures of the AAR antagonists V-2006 and CPI-444, novel 4-(furan-2-yl)-1H-pyrazolo[3,4-d]pyrimidin-6-amine derivatives were designed as such dual-acting compounds.

GPCR large-amplitude dynamics by F-NMR of aprepitant bound to the neurokinin 1 receptor.

Comparisons of G protein-coupled receptor (GPCR) complexes with agonists and antagonists based on X-ray crystallography and cryo-electron microscopy structure determinations show differences in the width of the orthosteric ligand binding groove over the range from 0.3 to 2.9 Å.

Brownian motion, spin diffusion and protein structure determination in solution.

This paper presents my recollections on the development of protein structure determination by NMR in solution from 1968 to 1992. The key to success was to identify NMR-accessible parameters that unambiguously determine the spatial arrangement of polypeptide chains. Inspired by work with cyclopeptides, model considerations showed that enforcing short non-bonding interatomic distances imposes «ring closure conditions» on polypeptide chains.

Design and preparation of the class B G protein-coupled receptors GLP-1R and GCGR for F-NMR studies in solution.

The human glucagon-like peptide-1 receptor (GLP-1R) and the glucagon receptor (GCGR) are class B G protein-coupled receptors (GPCRs) that are activated by interactions with, respectively, the glucagon-like peptide-1 (GLP-1) and glucagon (GCG). These polypeptide hormones are involved in the regulation of lipid and cholic acid metabolism, and thus play an important role in the pathogenesis of glucose metabolism and diabetes mellitus, which attracts keen interest of these GPCRs as drug targets. GLP-1R and GCGR have therefore been extensively investigated by X-ray crystallography and cryo-electron microscopy (cryo-EM), so that their structures are well known.

A Adenosine Receptor Partial Agonism Related to Structural Rearrangements in an Activation Microswitch.

In drug design, G protein-coupled receptor (GPCR) partial agonists enable one to fine-tune receptor output between basal and maximal signaling levels. Here, we add to the structural basis for rationalizing and monitoring partial agonism. NMR spectroscopy of partial agonist complexes of the A adenosine receptor (AAR) revealed conformations of the P-I-F activation motif that are distinctly different from full agonist complexes.

OCRE Domains of Splicing Factors RBM5 and RBM10: Tyrosine Ring-Flip Frequencies Determined by Integrated Use of H NMR Spectroscopy and Molecular Dynamics Simulations.

The 55-residue OCRE domains of the splicing factors RBM5 and RBM10 contain 15 tyrosines in compact, globular folds. At 25 °C, all 15 tyrosines show symmetric H NMR spectra, with averaged signals for the pairs of δ- and ϵ-ring hydrogens. At 4 °C, two tyrosines were identified as showing H NMR line-broadening due to lowered frequency of the ring-flipping.

Tumor Immunotherapy Using A Adenosine Receptor Antagonists.

The A adenosine receptor (AAR) plays critical roles in human physiology and pathophysiology, which makes it an important drug target. Previous drug-discovery efforts targeting the AAR have been focused on the use of AAR antagonists for the treatment of Parkinson's disease. More recently, the AAR has attracted additional attention for its roles in immuno-oncology, and a number of AAR antagonists are currently used as lead compounds for antitumor drugs in both preclinical models and clinical trials.

Biased Signaling of the G-Protein-Coupled Receptor βAR Is Governed by Conformational Exchange Kinetics.

G-protein-coupled receptors (GPCRs) mediate a wide range of human physiological functions by transducing extracellular ligand binding events into intracellular responses. GPCRs can activate parallel, independent signaling pathways mediated by G proteins or β-arrestins. Whereas "balanced" agonists activate both pathways equally, "biased" agonists dominantly activate one pathway, which is of interest for designing GPCR-targeting drugs because it may mitigate undesirable side effects.

Disulfide-Containing Detergents (DCDs) for the Structural Biology of Membrane Proteins.

Disulfide-containing detergents (DCDs) are introduced, which contain a disulfide bond in the hydrophobic tail. DCDs form smaller micelles than corresponding detergents with linear hydrocarbon chains, while providing good solubilization and reconstitution of membrane proteins. The use of this new class of detergents in structural biology is illustrated with solution NMR spectra of the human G protein-coupled receptor A AR, which is an α-helical protein, and the β-barrel protein OmpX from E.

Human substance P receptor binding mode of the antagonist drug aprepitant by NMR and crystallography.

Neurokinin 1 receptor (NK1R) has key regulating functions in the central and peripheral nervous systems, and NK1R antagonists such as aprepitant have been approved for treating chemotherapy-induced nausea and vomiting. However, the lack of data on NK1R structure and biochemistry has limited further drug development targeting this receptor. Here, we combine NMR spectroscopy and X-ray crystallography to provide dynamic and static characterisation of the binding mode of aprepitant in complexes with human NK1R variants.

A adenosine receptor functional states characterized by F-NMR.

The human proteome contains 826 G protein-coupled receptors (GPCR), which control a wide array of key physiological functions, making them important drug targets. GPCR functions are based on allosteric coupling from the extracellular orthosteric drug binding site across the cell membrane to intracellular binding sites for partners such as G proteins and arrestins. This signaling process is related to dynamic equilibria in conformational ensembles that can be observed by NMR in solution.

GPCR drug discovery: integrating solution NMR data with crystal and cryo-EM structures.

The 826 G protein-coupled receptors (GPCRs) in the human proteome regulate key physiological processes and thus have long been attractive drug targets. With the crystal structures of more than 50 different human GPCRs determined over the past decade, an initial platform for structure-based rational design has been established for drugs that target GPCRs, which is currently being augmented with cryo-electron microscopy (cryo-EM) structures of higher-order GPCR complexes. Nuclear magnetic resonance (NMR) spectroscopy in solution is one of the key approaches for expanding this platform with dynamic features, which can be accessed at physiological temperature and with minimal modification of the wild-type GPCR covalent structures.

Molecular interactions connecting the function of the serine-arginine-rich protein SRSF1 to protein phosphatase 1.

Splicing generates many mRNA strands from a single precursor mRNA, expanding the proteome and enhancing intracellular diversity. Both initial assembly and activation of the spliceosome require an essential family of splicing factors called serine-arginine (SR) proteins. Protein phosphatase 1 (PP1) regulates the SR proteins by controlling phosphorylation of a C-terminal arginine-serine-rich (RS) domain.