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Nature Structural & Molecular Biology Jan 2018G-protein-coupled receptors (GPCRs) relay numerous extracellular signals by triggering intracellular signaling through coupling with G proteins and arrestins. Recent... (Review)
Review
G-protein-coupled receptors (GPCRs) relay numerous extracellular signals by triggering intracellular signaling through coupling with G proteins and arrestins. Recent breakthroughs in the structural determination of GPCRs and GPCR-transducer complexes represent important steps toward deciphering GPCR signal transduction at a molecular level. A full understanding of the molecular basis of GPCR-mediated signaling requires elucidation of the dynamics of receptors and their transducer complexes as well as their energy landscapes and conformational transition rates. Here, we summarize current insights into the structural plasticity of GPCR-G-protein and GPCR-arrestin complexes that underlies the regulation of the receptor's intracellular signaling profile.
Topics: Allosteric Site; Animals; Electron Spin Resonance Spectroscopy; GTP-Binding Proteins; Humans; Ligands; Protein Binding; Protein Domains; Protein Structure, Secondary; Receptors, G-Protein-Coupled; Signal Transduction; beta-Arrestins
PubMed: 29323277
DOI: 10.1038/s41594-017-0011-7 -
Nature Sep 2021Olfactory systems must detect and discriminate amongst an enormous variety of odorants. To contend with this challenge, diverse species have converged on a common...
Olfactory systems must detect and discriminate amongst an enormous variety of odorants. To contend with this challenge, diverse species have converged on a common strategy in which odorant identity is encoded through the combinatorial activation of large families of olfactory receptors, thus allowing a finite number of receptors to detect a vast chemical world. Here we offer structural and mechanistic insight into how an individual olfactory receptor can flexibly recognize diverse odorants. We show that the olfactory receptor MhOR5 from the jumping bristletail Machilis hrabei assembles as a homotetrameric odorant-gated ion channel with broad chemical tuning. Using cryo-electron microscopy, we elucidated the structure of MhOR5 in multiple gating states, alone and in complex with two of its agonists-the odorant eugenol and the insect repellent DEET. Both ligands are recognized through distributed hydrophobic interactions within the same geometrically simple binding pocket located in the transmembrane region of each subunit, suggesting a structural logic for the promiscuous chemical sensitivity of this receptor. Mutation of individual residues lining the binding pocket predictably altered the sensitivity of MhOR5 to eugenol and DEET and broadly reconfigured the receptor's tuning. Together, our data support a model in which diverse odorants share the same structural determinants for binding, shedding light on the molecular recognition mechanisms that ultimately endow the olfactory system with its immense discriminatory capacity.
Topics: Animals; Binding Sites; Cell Line; DEET; Eugenol; Insect Proteins; Insecta; Ion Channel Gating; Ion Channels; Models, Molecular; Mutation; Odorants; Protein Binding; Protein Structure, Quaternary; Receptors, Odorant; Substrate Specificity
PubMed: 34349260
DOI: 10.1038/s41586-021-03794-8 -
ELife Nov 2012Human hepatitis B virus (HBV) infection and HBV-related diseases remain a major public health problem. Individuals coinfected with its satellite hepatitis D virus (HDV)...
Human hepatitis B virus (HBV) infection and HBV-related diseases remain a major public health problem. Individuals coinfected with its satellite hepatitis D virus (HDV) have more severe disease. Cellular entry of both viruses is mediated by HBV envelope proteins. The pre-S1 domain of the large envelope protein is a key determinant for receptor(s) binding. However, the identity of the receptor(s) is unknown. Here, by using near zero distance photo-cross-linking and tandem affinity purification, we revealed that the receptor-binding region of pre-S1 specifically interacts with sodium taurocholate cotransporting polypeptide (NTCP), a multiple transmembrane transporter predominantly expressed in the liver. Silencing NTCP inhibited HBV and HDV infection, while exogenous NTCP expression rendered nonsusceptible hepatocarcinoma cells susceptible to these viral infections. Moreover, replacing amino acids 157-165 of nonfunctional monkey NTCP with the human counterpart conferred its ability in supporting both viral infections. Our results demonstrate that NTCP is a functional receptor for HBV and HDV.DOI:http://dx.doi.org/10.7554/eLife.00049.001.
Topics: Amino Acid Sequence; Animals; Biological Transport; Cell Line; Gene Expression; Hepatitis B virus; Hepatitis Delta Virus; Hepatocytes; Humans; Liver; Molecular Sequence Data; Organic Anion Transporters, Sodium-Dependent; Peptides; Photochemical Processes; Primary Cell Culture; Protein Binding; Protein Structure, Tertiary; Receptors, Virus; Symporters; Taurocholic Acid; Tupaia; Viral Envelope Proteins; Virus Internalization
PubMed: 23150796
DOI: 10.7554/eLife.00049 -
ELife Oct 2022N-methyl-D-aspartate receptors (NMDARs) uniquely require binding of two different neurotransmitter agonists for synaptic transmission. D-serine and glycine bind to one...
N-methyl-D-aspartate receptors (NMDARs) uniquely require binding of two different neurotransmitter agonists for synaptic transmission. D-serine and glycine bind to one subunit, GluN1, while glutamate binds to the other, GluN2. These agonists bind to the receptor's bi-lobed ligand-binding domains (LBDs), which close around the agonist during receptor activation. To better understand the unexplored mechanisms by which D-serine contributes to receptor activation, we performed multi-microsecond molecular dynamics simulations of the GluN1/GluN2A LBD dimer with free D-serine and glutamate agonists. Surprisingly, we observed D-serine binding to both GluN1 and GluN2A LBDs, suggesting that D-serine competes with glutamate for binding to GluN2A. This mechanism is confirmed by our electrophysiology experiments, which show that D-serine is indeed inhibitory at high concentrations. Although free energy calculations indicate that D-serine stabilizes the closed GluN2A LBD, its inhibitory behavior suggests that it either does not remain bound long enough or does not generate sufficient force for ion channel gating. We developed a workflow using pathway similarity analysis to identify groups of residues working together to promote binding. These conformation-dependent pathways were not significantly impacted by the presence of N-linked glycans, which act primarily by interacting with the LBD bottom lobe to stabilize the closed LBD.
Topics: Receptors, N-Methyl-D-Aspartate; Glutamic Acid; Molecular Conformation; Molecular Dynamics Simulation; Serine
PubMed: 36301074
DOI: 10.7554/eLife.77645 -
ELife Jul 2023Receptors signal by switching between resting (C) and active (O) shapes ('gating') under the influence of agonists. The receptor's maximum response depends on the...
Receptors signal by switching between resting (C) and active (O) shapes ('gating') under the influence of agonists. The receptor's maximum response depends on the difference in agonist binding energy, O minus C. In nicotinic receptors, efficiency (η) represents the fraction of agonist binding energy applied to a local rearrangement (an induced fit) that initiates gating. In this receptor, free energy changes in gating and binding can be interchanged by the conversion factor η. Efficiencies estimated from concentration-response curves (23 agonists, 53 mutations) sort into five discrete classes (%): 0.56 (17), 0.51(32), 0.45(13), 0.41(26), and 0.31(12), implying that there are 5 C versus O binding site structural pairs. Within each class efficacy and affinity are corelated linearly, but multiple classes hide this relationship. η unites agonist binding with receptor gating and calibrates one link in a chain of coupled domain rearrangements that comprises the allosteric transition of the protein.
Topics: Receptors, Nicotinic; Binding Sites; Mutation
PubMed: 37399234
DOI: 10.7554/eLife.86496 -
Tropical Medicine and Health Dec 2011Dengue virus is an arthropod-borne virus transmitted by Aedes mosquitoes. Dengue virus causes fever and hemorrhagic disorders in humans and non-human primates. Direct...
Dengue virus is an arthropod-borne virus transmitted by Aedes mosquitoes. Dengue virus causes fever and hemorrhagic disorders in humans and non-human primates. Direct interaction of the virus introduced by a mosquito bite with host receptor molecule(s) is crucial for virus propagation and the pathological progression of dengue diseases. Therefore, elucidation of the molecular mechanisms underlying the interaction between dengue virus and its receptor(s) in both humans and mosquitoes is essential for an understanding of dengue pathology. In addition, understanding the molecular mechanism(s) of virus entry is crucial for the development of effective new therapies to treat dengue patients. Binding of dengue virus to its receptor molecules is mediated through a viral envelope glycoprotein, termed E protein. We present a summary and describe the structures, binding properties, and pathological relevance of dengue virus receptor molecules proposed to date. In mammalian cells, there are many candidate molecules that may act as receptors, such as sulfated glycosaminoglycans (GAGs), lectins that recognize carbohydrates, glycosphingolipid (GSL), proteins with chaperone activity, laminin-binding proteins, and other uncharacterized proteins. There are also several lines of evidence for receptor molecules such as GSLs, proteins with chaperone activity, laminin-binding proteins, and other uncharacterized proteins in mosquito cells and organs. This review focuses on several molecules involved in carbohydrate-dependent binding of the virus.
PubMed: 22500135
DOI: 10.2149/tmh.2011-S03 -
Frontiers in Molecular Neuroscience 2022Morphine remains the gold standard painkiller available to date to relieve severe pain. Morphine metabolism leads to the production of two predominant metabolites,... (Review)
Review
Morphine remains the gold standard painkiller available to date to relieve severe pain. Morphine metabolism leads to the production of two predominant metabolites, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G). This metabolism involves uridine 5'-diphospho-glucuronosyltransferases (UGTs), which catalyze the addition of a glucuronide moiety onto the C3 or C6 position of morphine. Interestingly, M3G and M6G have been shown to be biologically active. On the one hand, M6G produces potent analgesia in rodents and humans. On the other hand, M3G provokes a state of strong excitation in rodents, characterized by thermal hyperalgesia and tactile allodynia. Its coadministration with morphine or M6G also reduces the resulting analgesia. Although these behavioral effects show quite consistency in rodents, M3G effects are much more debated in humans and the identity of the receptor(s) on which M3G acts remains unclear. Indeed, M3G has little affinity for mu opioid receptor (MOR) (on which morphine binds) and its effects are retained in the presence of naloxone or naltrexone, two non-selective MOR antagonists. Paradoxically, MOR seems to be essential to M3G effects. In contrast, several studies proposed that TLR4 could mediate M3G effects since this receptor also appears to be essential to M3G-induced hyperalgesia. This review summarizes M3G's behavioral effects and potential targets in the central nervous system, as well as the mechanisms by which it might oppose analgesia.
PubMed: 35645730
DOI: 10.3389/fnmol.2022.882443 -
Current Opinion in Structural Biology Dec 2016G protein-coupled receptors (GPCRs) respond to extracellular stimuli and interact with several intracellular binding partners to elicit cellular responses, including... (Review)
Review
G protein-coupled receptors (GPCRs) respond to extracellular stimuli and interact with several intracellular binding partners to elicit cellular responses, including heterotrimeric G proteins. Recent structural and biophysical studies have highlighted the dynamic nature of GPCRs and G proteins and have identified specific conformational changes important for receptor-mediated nucleotide exchange on Gα. While domain separation within Gα is necessary for GDP release, opening the inter-domain interface is insufficient to stimulate nucleotide exchange. Rather, an activated receptor promotes GDP release by allosterically disrupting the nucleotide-binding site via interactions with the Gα N-termini and C-termini. Highlighting the allosteric nature of GPCRs, recent studies suggest that agonist binding alone poorly stabilizes an active conformation of several receptors. Rather, full stabilization of the receptor in an active state requires formation of the agonist-receptor-G protein ternary complex. In turn, nucleotide-free Gα is able to stabilize conformational changes around the receptor's agonist-binding site to enhance agonist affinity.
Topics: Binding Sites; GTP-Binding Proteins; Humans; Nucleotides; Protein Binding; Protein Domains; Receptors, G-Protein-Coupled
PubMed: 27871057
DOI: 10.1016/j.sbi.2016.11.005 -
Cells Jun 2023The glucocorticoid receptor α (GRα) is a member of the nuclear receptor superfamily and functions as a glucocorticoid (GC)-responsive transcription factor. GR can halt... (Review)
Review
The glucocorticoid receptor α (GRα) is a member of the nuclear receptor superfamily and functions as a glucocorticoid (GC)-responsive transcription factor. GR can halt inflammation and kill off cancer cells, thus explaining the widespread use of glucocorticoids in the clinic. However, side effects and therapy resistance limit GR's therapeutic potential, emphasizing the importance of resolving all of GR's context-specific action mechanisms. Fortunately, the understanding of GR structure, conformation, and stoichiometry in the different GR-controlled biological pathways is now gradually increasing. This information will be crucial to close knowledge gaps on GR function. In this review, we focus on the various domains and mechanisms of action of GR, all from a structural perspective.
Topics: Humans; Glucocorticoids; Receptors, Glucocorticoid; Transcription Factors
PubMed: 37371105
DOI: 10.3390/cells12121636 -
Molecules and Cells Apr 2016Epstein-Barr virus (EBV) is the prototypical γ-herpesvirus and an obligate human pathogen that infects mainly epithelial cells and B cells, which can result in... (Review)
Review
Epstein-Barr virus (EBV) is the prototypical γ-herpesvirus and an obligate human pathogen that infects mainly epithelial cells and B cells, which can result in malignancies. EBV infects these target cells by fusing with the viral and cellular lipid bilayer membranes using multiple viral factors and host receptor(s) thus exhibiting a unique complexity in its entry machinery. To enter epithelial cells, EBV requires minimally the conserved core fusion machinery comprised of the glycoproteins gH/gL acting as the receptor-binding complex and gB as the fusogen. EBV can enter B cells using gp42, which binds tightly to gH/gL and interacts with host HLA class II, activating fusion. Previously, we published the individual crystal structures of EBV entry factors, such as gH/gL and gp42, the EBV/host receptor complex, gp42/HLA-DR1, and the fusion protein EBV gB in a postfusion conformation, which allowed us to identify structural determinants and regions critical for receptor-binding and membrane fusion. Recently, we reported different low resolution models of the EBV B cell entry triggering complex (gHgL/gp42/HLA class II) in "open" and "closed" states based on negative-stain single particle electron microscopy, which provide further mechanistic insights. This review summarizes the current knowledge of these key players in EBV entry and how their structures impact receptor-binding and the triggering of gB-mediated fusion.
Topics: B-Lymphocytes; Cell Line; Epithelial Cells; Genes, MHC Class II; Herpesvirus 4, Human; Histocompatibility Antigens Class II; Humans; Models, Molecular; Protein Structure, Tertiary; Viral Fusion Proteins; Viral Tropism; Virus Internalization
PubMed: 27094060
DOI: 10.14348/molcells.2016.0066