Peptide ligand recognition by G protein-coupled receptors

Introduction: This study was conducted to investigate the effects of thyme extract in drinking water on immune response of broiler chickens. Methods: A total of 245-day-old broiler chicks were purchased and 20 chicks were bled for determination maternal antibody and remaining chicks were divided into 5 equal groups. Chickens of group A, B and C received 0.1%, 0.15% and 0.2% of Pediatric Cough Syrup including thyme extract respectively in drinking water for all of the experimental period. Chickens of group D were not received Pediatric Cough Syrup but vaccinated against Influenza disease. Chickens of group E were kept as control group and were not received Pediatric Cough Syrup and Influenza disease vaccine. Chickens of group A, B, C and D were vaccinated with AI-ND killed vaccine (subtype H9N2), subcutaneously in neck back. Blood samples were collected before vaccination as well as on days 14, 28 and 35 after vaccination. Ten chickens of each group were bled randomly and antibody titer against influenza vaccine virus was determined by hemagglutination inhibition (HI) test. Results: The results of the present study showed that Pediatric Cough Syrup including thyme extract at 0.2%, increased the specific antibody response against Influenza vaccine virus compared to all groups. Conclusion: Pediatric Cough Syrup including thyme extract can improve the specific antibody response against Influenza vaccine virus

Structure and dynamics of a constitutively active neurotensin receptor

Many G protein-coupled receptors show constitutive activity, resulting in the production of a second messenger in the absence of an agonist; and naturally occurring constitutively active mutations in receptors have been implicated in diseases. To gain insight into mechanistic aspects of constitutive activity, we report here the 3.3 Å crystal structure of a constitutively active, agonist-bound neurotensin receptor (NTSR1) and molecular dynamics simulations of agonist-occupied and ligand-free receptor. Comparison with the structure of a NTSR1 variant that has little constitutive activity reveals uncoupling of the ligand-binding domain from conserved connector residues, that effect conformational changes during GPCR activation. Furthermore, molecular dynamics simulations show strong contacts between connector residue side chains and increased flexibility at the intracellular receptor face as features that coincide with robust signalling in cells. The loss of correlation between the binding pocket and conserved connector residues, combined with altered receptor dynamics, possibly explains the reduced neurotensin efficacy in the constitutively active NTSR1 and a facilitated initial engagement with G protein in the absence of agonist

Ligand and G-protein selectivity in the κ-opioid receptor

The κ-opioid receptor (KOR) represents a highly desirable therapeutic target for treating not only pain but also addiction and affective disorder

Molecular mechanism of biased signaling at the kappa opioid receptor

The κ-opioid receptor (KOR) has emerged as an attractive drug target for pain management without addiction, and biased signaling through particular pathways of KOR may be key to maintaining this benefit while minimizing side-effect liabilities. As for most G protein-coupled receptors (GPCRs), however, the molecular mechanisms of ligand-specific signaling at KOR have remained unclear. To better understand the molecular determinants of KOR signaling bias, we apply structure determination, atomic-level molecular dynamics (MD) simulations, and functional assays. We determine a crystal structure of KOR bound to the G protein-biased agonist nalfurafine, the first approved KOR-targeting drug. We also identify an arrestin-biased KOR agonist, WMS-X600. Using MD simulations of KOR bound to nalfurafine, WMS-X600, and a balanced agonist U50,488, we identify three active-state receptor conformations, including one that appears to favor arrestin signaling over G protein signaling and another that appears to favor G protein signaling over arrestin signaling. These results, combined with mutagenesis validation, provide a molecular explanation of how agonists achieve biased signaling at KOR

Language of Lullabies: The Russification and De-Russification of the Baltic States

This article argues that the laws for promotion of the national languages are a legitimate means for the Baltic states to establish their cultural independence from Russia and the former Soviet Union

Peptide ligand recognition by G protein-coupled receptors

The past few years have seen spectacular progress in the structure determination of G protein-coupled receptors (GPCRs). We now have structural representatives from classes A, B, C, and F. Within the rhodopsin-like class A, most structures belong to the α group, whereas fewer GPCR structures are available from the β, γ, and δ groups, which include peptide GPCRs such as the receptors for neurotensin (β group), opioids, chemokines (γ group), and protease-activated receptors (δ group). Structural information on peptide GPCRs is restricted to complexes with non-peptidic drug-like antagonists with the exception of the chemokine receptor CXCR4 that has been crystallized in the presence of a cyclic peptide antagonist. Notably, the neurotensin receptor (NTSR1) is to date the only peptide GPCR whose structure has been solved in the presence of a peptide agonist. Although limited in number, the current peptide GPCR structures reveal great diversity in shape and electrostatic properties of the ligand binding pockets, features that play key roles in the discrimination of ligands. Here, we review these aspects of peptide GPCRs in view of possible models for peptide agonist binding

Structure of a Hallucinogen-Activated Gq-Coupled 5-HT2A Serotonin Receptor

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

Inactive and active state structures template selective tools for the human 5-HT5A receptor

Serotonin receptors are important targets for established therapeutics and drug development as they are expressed throughout the human body and play key roles in cell signaling. There are 12 serotonergic G protein-coupled receptor members encoded in the human genome, of which the 5-hydroxytryptamine (5-HT)5A receptor (5-HT5AR) is the least understood and lacks selective tool compounds. Here, we report four high-resolution (2.73-2.80 Å) structures of human 5-HT5ARs, including an inactive state structure bound to an antagonist AS2674723 by crystallization and active state structures bound to a partial agonist lisuride and two full agonists, 5-carboxamidotryptamine (5-CT) and methylergometrine, by cryo-EM. Leveraging the new structures, we developed a highly selective and potent antagonist for 5-HT5AR. Collectively, these findings both enhance our understanding of this enigmatic receptor and provide a roadmap for structure-based drug discovery for 5-HT5AR

Structure, function and pharmacology of human itch GPCRs.

The MRGPRX family of receptors (MRGPRX1-4) is a family of mas-related G-protein-coupled receptors that have evolved relatively recently1. Of these, MRGPRX2 and MRGPRX4 are key physiological and pathological mediators of itch and related mast cell-mediated hypersensitivity reactions2-5. MRGPRX2 couples to both Gi and Gq in mast cells6. Here we describe agonist-stabilized structures of MRGPRX2 coupled to Gi1 and Gq in ternary complexes with the endogenous peptide cortistatin-14 and with a synthetic agonist probe, respectively, and the development of potent antagonist probes for MRGPRX2. We also describe a specific MRGPRX4 agonist and the structure of this agonist in a complex with MRGPRX4 and Gq. Together, these findings should accelerate the structure-guided discovery of therapeutic agents for pain, itch and mast cell-mediated hypersensitivity