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The X-ray crystal structure of the M3 muscarinic acetylcholine receptor bound to the bronchodilator drug tiotropium is reported; comparison of this structure with that of the M2 muscarinic acetylcholine receptor reveals key differences that could potentially be exploited to develop subtype-selective drugs. Muscrarinic receptor structures compared The muscarinic acetylcholine receptors (mAChRs) constitute a family of G-protein-coupled receptors. These membrane proteins are targets for treatment of a broad range of conditions, including Alzheimer's disease, schizophrenia and chronic obstructive pulmonary disease. The five mAChR subtypes (M1–M5) share a high degree of sequence homology, but show marked differences in G-protein-coupling preference and physiological function. This pair of papers from Brian Kobilka's group presents the structures of two of the five subtypes. Haga et al . report the X-ray crystal structure of the M2 receptor, which is essential for the physiological control of cardiovascular function; Kruse et al . determine the structure of the M3 receptor, active in the bronchial airways and elsewhere. Comparison of the two structures reveals key differences that could potentially be exploited to develop subtype-selective drugs. Acetylcholine, the first neurotransmitter to be identified 1 , exerts many of its physiological actions via activation of a family of G-protein-coupled receptors (GPCRs) known as muscarinic acetylcholine receptors (mAChRs). Although the five mAChR subtypes (M1–M5) share a high degree of sequence homology, they show pronounced differences in G-protein coupling preference and the physiological responses they mediate 2 , 3 , 4 . Unfortunately, despite decades of effort, no therapeutic agents endowed with clear mAChR subtype selectivity have been developed to exploit these differences 5 , 6 . We describe here the structure of the G q/11 -coupled M3 mAChR (‘M3 receptor’, from rat) bound to the bronchodilator drug tiotropium and identify the binding mode for this clinically important drug. This structure, together with that of the G i/o -coupled M2 receptor 7 , offers possibilities for the design of mAChR subtype-selective ligands. Importantly, the M3 receptor structure allows a structural comparison between two members of a mammalian GPCR subfamily displaying different G-protein coupling selectivities. Furthermore, molecular dynamics simulations suggest that tiotropium binds transiently to an allosteric site en route to the binding pocket of both receptors. These simulations offer a structural view of an allosteric binding mode for an orthosteric GPCR ligand and provide additional opportunities for the design of ligands with different affinities or binding kinetics for different mAChR subtypes. Our findings not only offer insights into the structure and function of one of the most important GPCR families, but may also facilitate the design of improved therapeutics targeting these critical receptors.

Binding modes and molecular mechanisms of several allosteric modulators of a prototypical G-protein-coupled receptor are revealed using atomic-level simulations and validated by the rational design of a modulator with substantially altered effects. Allosteric mechanism of GPCR modulation A third of clinically used drugs elicit their biological effects via a G-protein-coupled receptor (GPCR), usually by binding at the orthosteric (primary ligand-binding) site, in competition with the ligands that naturally regulate receptor signalling. The design of small molecules able to selectively modulate a GPCR by binding to an allosteric site is a desirable goal, but difficult to achieve because neither the binding modes nor the molecular mechanisms of such molecules are known. In this manuscript, the authors used molecular dynamics simulations, with experimental validation, to determine where and how structurally diverse allosteric modulators bind to the M2 muscarinic acetylcholine receptor, which is essential for the physiological control of cardiovascular function. Despite substantial structural diversity of the small molecule ligands, the molecules all formed cation-π interactions with clusters of aromatic residues in the receptor's extracellular vestibule, about 15 Å from the ligand-binding pocket. These findings may facilitate the rational design of allosteric modulators targeting muscarinic and related GPCRs. The design of G-protein-coupled receptor (GPCR) allosteric modulators, an active area of modern pharmaceutical research, has proved challenging because neither the binding modes nor the molecular mechanisms of such drugs are known 1 , 2 . Here we determine binding sites, bound conformations and specific drug–receptor interactions for several allosteric modulators of the M2 muscarinic acetylcholine receptor (M2 receptor), a prototypical family A GPCR, using atomic-level simulations in which the modulators spontaneously associate with the receptor. Despite substantial structural diversity, all modulators form cation–π interactions with clusters of aromatic residues in the receptor extracellular vestibule, approximately 15 Å from the classical, ‘orthosteric’ ligand-binding site. We validate the observed modulator binding modes through radioligand binding experiments on receptor mutants designed, on the basis of our simulations, either to increase or to decrease modulator affinity. Simulations also revealed mechanisms that contribute to positive and negative allosteric modulation of classical ligand binding, including coupled conformational changes of the two binding sites and electrostatic interactions between ligands in these sites. These observations enabled the design of chemical modifications that substantially alter a modulator’s allosteric effects. Our findings thus provide a structural basis for the rational design of allosteric modulators targeting muscarinic and possibly other GPCRs.

Protease-activated receptor 1 (PAR1) is the prototypical member of a family of G-protein-coupled receptors that mediate cellular responses to thrombin and related proteases. Thrombin irreversibly activates PAR1 by cleaving the amino-terminal exodomain of the receptor, which exposes a tethered peptide ligand that binds the heptahelical bundle of the receptor to affect G-protein activation. Here we report the 2.2-Å-resolution crystal structure of human PAR1 bound to vorapaxar, a PAR1 antagonist. The structure reveals an unusual mode of drug binding that explains how a small molecule binds virtually irreversibly to inhibit receptor activation by the tethered ligand of PAR1. In contrast to deep, solvent-exposed binding pockets observed in other peptide-activated G-protein-coupled receptors, the vorapaxar-binding pocket is superficial but has little surface exposed to the aqueous solvent. Protease-activated receptors are important targets for drug development. The structure reported here will aid the development of improved PAR1 antagonists and the discovery of antagonists to other members of this receptor family. The X-ray crystal structure of the human G-protein-coupled receptor protease-activated receptor 1 (PAR1) bound to the antagonist vorapaxar is solved, revealing an unusual method of drug binding that should facilitate the development of improved PAR1-selective antagonists. Thrombin receptor structure The X-ray crystal structure of the human protease-activated receptor 1 (PAR1) bound to vorapaxar, a PAR1 antagonist, has been determined at 2.2 Å resolution. PAR1, also known as the thrombin receptor, is a G protein-coupled receptor that mediates cellular responses to the coagulation protease thrombin and related proteases. Vorapaxar was recently shown to prevent myocardial infarction in at-risk patients, and knowledge of the PAR structure will be relevant to the design of PAR1 antagonists with better drug properties.

Binding modes and molecular mechanisms of several allosteric modulators of a prototypical G-protein-coupled receptor are revealed using atomic-level simulations and validated by the rational design of a modulator with substantially altered effects.

Protease-Activated Receptor-1 (PAR1) is the prototypical member of a family of G protein-coupled receptors that mediate cellular responses to thrombin and related proteases. Thrombin irreversibly activates PAR1 by cleaving the N-terminal exodomain of the receptor, which exposes a tethered peptide ligand that binds the receptor’s heptahelical bundle to effect G protein-activation. Here we report a 2.2Å resolution crystal structure of human PAR1 bound to vorapaxar, a PAR1 antagonist. The structure reveals an unusual mode of drug binding that explains how a small molecule binds virtually irreversibly to inhibit receptor activation by PAR1’s tethered ligand. In contrast to deep, solvent-exposed binding pockets observed in other peptide-activated GPCRs, the vorapaxar-binding pocket is superficial but has little surface exposed to the aqueous solvent. PARs are important targets for drug development. The structure reported here will aid development of improved PAR1 antagonists and discovery of antagonists to other members of this receptor family.

We present a genome-wide association study of ileal Crohn disease and two independent replication studies that identify several new regions of association to Crohn disease. Specifically, in addition to the previously established CARD15 and IL23R associations, we identified strong and significantly replicated associations (combined P < 10 −10 ) with an intergenic region on 10q21.1 and a coding variant in ATG16L1 , the latter of which was also recently reported by another group. We also report strong associations with independent replication to variation in the genomic regions encoding PHOX2B , NCF4 and a predicted gene on 16q24.1 ( FAM92B ). Finally, we demonstrate that ATG16L1 is expressed in intestinal epithelial cell lines and that functional knockdown of this gene abrogates autophagy of Salmonella typhimurium . Together, these findings suggest that autophagy and host cell responses to intracellular microbes are involved in the pathogenesis of Crohn disease.

Characterising associations between the methylome, proteome and phenome may provide insight into biological pathways governing brain health. Here, we report an integrated DNA methylation and phenotypic study of the circulating proteome in relation to brain health. Methylome-wide association studies of 4058 plasma proteins are performed ( N  = 774), identifying 2928 CpG-protein associations after adjustment for multiple testing. These are independent of known genetic protein quantitative trait loci (pQTLs) and common lifestyle effects. Phenome-wide association studies of each protein are then performed in relation to 15 neurological traits ( N  = 1,065), identifying 405 associations between the levels of 191 proteins and cognitive scores, brain imaging measures or APOE e4 status. We uncover 35 previously unreported DNA methylation signatures for 17 protein markers of brain health. The epigenetic and proteomic markers we identify are pertinent to understanding and stratifying brain health. Characterising associations between the methylome, proteome and phenome may provide insight into biological pathways governing brain health. Here, blood protein markers of brain health are integrated with omics data to reveal DNA methylation differences that associate with these protein markers.

Childhood trauma and adversity are common across societies and have strong associations with physical and psychiatric morbidity throughout the life-course. One possible mechanism through which childhood trauma may predispose individuals to poor psychiatric outcomes is via associations with brain structure. This study aimed to elucidate the associations between childhood trauma and brain structure across two large, independent community cohorts. The two samples comprised (i) a subsample of Generation Scotland (n=1,024); and (ii) individuals from UK Biobank (n=27,202). This comprised n=28,226 for mega-analysis. MRI scans were processed using Free Surfer, providing cortical, subcortical, and global brain metrics. Regression models were used to determine associations between childhood trauma measures and brain metrics and psychiatric phenotypes. Childhood trauma associated with lifetime depression across cohorts (OR 1.06 GS, 1.23 UKB), and related to early onset and recurrent course within both samples. There was evidence for associations between childhood trauma and structural brain metrics. This included reduced global brain volume, and reduced cortical surface area with highest effects in the frontal (β=-0.0385, SE=0.0048, p(FDR)=5.43x10-15) and parietal lobes (β=-0.0387, SE=0.005, p(FDR)=1.56x10-14). At a regional level the ventral diencephalon (VDc) displayed significant associations with childhood trauma measures across both cohorts and at mega-analysis (β=-0.0232, SE=0.0039, p(FDR)=2.91x10-8). There were also associations with reduced hippocampus, thalamus, and nucleus accumbens volumes. Associations between childhood trauma and reduced global and regional brain volumes were found, across two independent UK cohorts, and at mega-analysis. This provides robust evidence for a lasting effect of childhood adversity on brain structure.

To understand the health impact of long-duration spaceflight, one identical twin astronaut was monitored before, during, and after a 1-year mission onboard the International Space Station; his twin served as a genetically matched ground control. Longitudinal assessments identified spaceflight-specific changes, including decreased body mass, telomere elongation, genome instability, carotid artery distension and increased intima-media thickness, altered ocular structure, transcriptional and metabolic changes, DNA methylation changes in immune and oxidative stress-related pathways, gastrointestinal microbiota alterations, and some cognitive decline postflight. Although average telomere length, global gene expression, and microbiome changes returned to near preflight levels within 6 months after return to Earth, increased numbers of short telomeres were observed and expression of some genes was still disrupted. These multiomic, molecular, physiological, and behavioral datasets provide a valuable roadmap of the putative health risks for future human spaceflight.

During July 2021, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.617.2 variant infections, including vaccine breakthrough infections, occurred after large public gatherings in Provincetown, Massachusetts, USA, prompting a multistate investigation. Public health departments identified primary and secondary cases by using coronavirus disease surveillance data, case investigations, and contact tracing. A primary case was defined as SARS-CoV-2 detected <14 days after travel to or residence in Provincetown during July 3-17. A secondary case was defined as SARS-CoV-2 detected <14 days after close contact with a person who had a primary case but without travel to or residence in Provincetown during July 3-August 10. We identified 1,098 primary cases and 30 secondary cases associated with 26 primary cases among fully and non-fully vaccinated persons. Large gatherings can have widespread effects on SARS-CoV-2 transmission, and fully vaccinated persons should take precautions, such as masking, to prevent SARS-CoV-2 transmission, particularly during substantial or high transmission.