Helene Irwin Fagan Chair in Cardiology


  • How GPCR Phosphorylation Patterns Orchestrate Arrestin-Mediated Signaling. Cell Latorraca, N. R., Masureel, M., Hollingsworth, S. A., Heydenreich, F. M., Suomivuori, C., Brinton, C., Townshend, R. J., Bouvier, M., Kobilka, B. K., Dror, R. O. 2020


    Binding of arrestin to phosphorylated G-protein-coupled receptors (GPCRs) controls many aspects of cell signaling. The number and arrangement of phosphates may vary substantially for a given GPCR, and different phosphorylation patterns trigger different arrestin-mediated effects. Here, we determine how GPCR phosphorylation influences arrestin behavior by using atomic-level simulations and site-directed spectroscopy to reveal the effects of phosphorylation patterns on arrestin binding and conformation. We find that patterns favoring binding differ from those favoring activation-associated conformational change. Both binding and conformation depend more on arrangement of phosphates than on their total number, with phosphorylation at different positions sometimes exerting opposite effects. Phosphorylation patterns selectively favor a wide variety of arrestin conformations, differently affecting arrestin sites implicated in scaffolding distinct signaling proteins. We also reveal molecular mechanisms of these phenomena. Our work reveals the structural basis for the long-standing "barcode" hypothesis and has important implications for design of functionally selective GPCR-targeted drugs.

    View details for DOI 10.1016/j.cell.2020.11.014

    View details for PubMedID 33296703

  • Viewing rare conformations of the beta2 adrenergic receptor with pressure-resolved DEER spectroscopy. Proceedings of the National Academy of Sciences of the United States of America Lerch, M. T., Matt, R. A., Masureel, M., Elgeti, M., Kumar, K. K., Hilger, D., Foys, B., Kobilka, B. K., Hubbell, W. L. 2020


    The beta2 adrenergic receptor (beta2AR) is an archetypal G protein coupled receptor (GPCR). One structural signature of GPCR activation is a large-scale movement (ca. 6 to 14 A) of transmembrane helix 6 (TM6) to a conformation which binds and activates a cognate G protein. The beta2AR exhibits a low level of agonist-independent G protein activation. The structural origin of this basal activity and its suppression by inverse agonists is unknown but could involve a unique receptor conformation that promotes G protein activation. Alternatively, a conformational selection model proposes that a minor population of the canonical active receptor conformation exists in equilibrium with inactive forms, thus giving rise to basal activity of the ligand-free receptor. Previous spin-labeling and fluorescence resonance energy transfer experiments designed to monitor the positional distribution of TM6 did not detect the presence of the active conformation of ligand-free beta2AR. Here we employ spin-labeling and pressure-resolved double electron-electron resonance spectroscopy to reveal the presence of a minor population of unliganded receptor, with the signature outward TM6 displacement, in equilibrium with inactive conformations. Binding of inverse agonists suppresses this population. These results provide direct structural evidence in favor of a conformational selection model for basal activity in beta2AR and provide a mechanism for inverse agonism. In addition, they emphasize 1) the importance of minor populations in GPCR catalytic function; 2) the use of spin-labeling and variable-pressure electron paramagnetic resonance to reveal them in a membrane protein; and 3) the quantitative evaluation of their thermodynamic properties relative to the inactive forms, including free energy, partial molar volume, and compressibility.

    View details for DOI 10.1073/pnas.2013904117

    View details for PubMedID 33257561

  • Structural basis for GLP-1 receptor activation by LY3502970, an orally active nonpeptide agonist. Proceedings of the National Academy of Sciences of the United States of America Kawai, T., Sun, B., Yoshino, H., Feng, D., Suzuki, Y., Fukazawa, M., Nagao, S., Wainscott, D. B., Showalter, A. D., Droz, B. A., Kobilka, T. S., Coghlan, M. P., Willard, F. S., Kawabe, Y., Kobilka, B. K., Sloop, K. W. 2020


    Glucagon-like peptide-1 receptor (GLP-1R) agonists are efficacious antidiabetic medications that work by enhancing glucose-dependent insulin secretion and improving energy balance. Currently approved GLP-1R agonists are peptide based, and it has proven difficult to obtain small-molecule activators possessing optimal pharmaceutical properties. We report the discovery and mechanism of action of LY3502970 (OWL833), a nonpeptide GLP-1R agonist. LY3502970 is a partial agonist, biased toward G protein activation over beta-arrestin recruitment at the GLP-1R. The molecule is highly potent and selective against other class B G protein-coupled receptors (GPCRs) with a pharmacokinetic profile favorable for oral administration. A high-resolution structure of LY3502970 in complex with active-state GLP-1R revealed a unique binding pocket in the upper helical bundle where the compound is bound by the extracellular domain (ECD), extracellular loop 2, and transmembrane helices 1, 2, 3, and 7. This mechanism creates a distinct receptor conformation that may explain the partial agonism and biased signaling of the compound. Further, interaction between LY3502970 and the primate-specific Trp33 of the ECD informs species selective activity for the molecule. In efficacy studies, oral administration of LY3502970 resulted in glucose lowering in humanized GLP-1R transgenic mice and insulinotropic and hypophagic effects in nonhuman primates, demonstrating an effect size in both models comparable to injectable exenatide. Together, this work determined the molecular basis for the activity of an oral agent being developed for the treatment of type 2 diabetes mellitus, offering insights into the activation of class B GPCRs by nonpeptide ligands.

    View details for DOI 10.1073/pnas.2014879117

    View details for PubMedID 33177239

  • Analysis of beta2AR-Gs and beta2AR-Gi complex formation by NMR spectroscopy. Proceedings of the National Academy of Sciences of the United States of America Ma, X., Hu, Y., Batebi, H., Heng, J., Xu, J., Liu, X., Niu, X., Li, H., Hildebrand, P. W., Jin, C., Kobilka, B. K. 2020


    The beta2-adrenergic receptor (beta2AR) is a prototypical G protein-coupled receptor (GPCR) that preferentially couples to the stimulatory G protein Gs and stimulates cAMP formation. Functional studies have shown that the beta2AR also couples to inhibitory G protein Gi, activation of which inhibits cAMP formation [R. P. Xiao, Sci. STKE 2001, re15 (2001)]. A crystal structure of the beta2AR-Gs complex revealed the interaction interface of beta2AR-Gs and structural changes upon complex formation [S. G. Rasmussen et al., Nature 477, 549-555 (2011)], yet, the dynamic process of the beta2AR signaling through Gs and its preferential coupling to Gs over Gi is still not fully understood. Here, we utilize solution nuclear magnetic resonance (NMR) spectroscopy and supporting molecular dynamics (MD) simulations to monitor the conformational changes in the G protein coupling interface of the beta2AR in response to the full agonist BI-167107 and Gs and Gi1 These results show that BI-167107 stabilizes conformational changes in four transmembrane segments (TM4, TM5, TM6, and TM7) prior to coupling to a G protein, and that the agonist-bound receptor conformation is different from the G protein coupled state. While most of the conformational changes observed in the beta2AR are qualitatively the same for Gs and Gi1, we detected distinct differences between the beta2AR-Gs and the beta2AR-Gi1 complex in intracellular loop 2 (ICL2). Interactions with ICL2 are essential for activation of Gs These differences between the beta2AR-Gs and beta2AR-Gi1 complexes in ICL2 may be key determinants for G protein coupling selectivity.

    View details for DOI 10.1073/pnas.2009786117

    View details for PubMedID 32868434

  • Author Correction: Structural insights into mu-opioid receptor activation. Nature Huang, W., Manglik, A., Venkatakrishnan, A. J., Laeremans, T., Feinberg, E. N., Sanborn, A. L., Kato, H. E., Livingston, K. E., Thorsen, T. S., Kling, R. C., Granier, S., Gmeiner, P., Husbands, S. M., Traynor, J. R., Weis, W. I., Steyaert, J., Dror, R. O., Kobilka, B. K. 2020


    An amendment to this paper has been published and can be accessed via a link at the top of the paper.

    View details for DOI 10.1038/s41586-020-2542-z

    View details for PubMedID 32724208

  • Structural insights into probe-dependent positive allosterism of the GLP-1 receptor. Nature chemical biology Bueno, A. B., Sun, B., Willard, F. S., Feng, D., Ho, J. D., Wainscott, D. B., Showalter, A. D., Vieth, M., Chen, Q., Stutsman, C., Chau, B., Ficorilli, J., Agejas, F. J., Cumming, G. R., Jimenez, A., Rojo, I., Kobilka, T. S., Kobilka, B. K., Sloop, K. W. 2020


    Drugs that promote the association of protein complexes are an emerging therapeutic strategy. We report discovery of a G protein-coupled receptor (GPCR) ligand that stabilizes an active state conformation by cooperatively binding both the receptor and orthosteric ligand, thereby acting as a 'molecular glue'. LSN3160440 is a positive allosteric modulator of the GLP-1R optimized to increase the affinity and efficacy of GLP-1(9-36), a proteolytic product of GLP-1(7-36). The compound enhances insulin secretion in a glucose-, ligand- and GLP-1R-dependent manner. Cryo-electron microscopy determined the structure of the GLP-1R bound to LSN3160440 in complex with GLP-1 and heterotrimeric Gs. The modulator binds high in the helical bundle at an interface between TM1 and TM2, allowing access to the peptide ligand. Pharmacological characterization showed strong probe dependence of LSN3160440 for GLP-1(9-36) versus oxyntomodulin that is driven by a single residue. Our findings expand protein-protein modulation drug discovery to uncompetitive, active state stabilizers for peptide hormone receptors.

    View details for DOI 10.1038/s41589-020-0589-7

    View details for PubMedID 32690941

  • An allosteric modulator binds to a conformational hub in the beta2 adrenergic receptor. Nature chemical biology Liu, X., Kaindl, J., Korczynska, M., StoSSel, A., Dengler, D., Stanek, M., Hubner, H., Clark, M. J., Mahoney, J., Matt, R. A., Xu, X., Hirata, K., Shoichet, B. K., Sunahara, R. K., Kobilka, B. K., Gmeiner, P. 2020


    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 beta2-adrenergic receptor (beta2AR), 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 E1223.41 and the backbone carbonyls of V2065.45 and S2075.46. The AS408 binding site is adjacent to a previously identified molecular switch for beta2AR activation formed by I3.40, P5.50 and F6.44. 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.

    View details for DOI 10.1038/s41589-020-0549-2

    View details for PubMedID 32483378

  • Activation of the alpha2B adrenoceptor by the sedative sympatholytic dexmedetomidine. Nature chemical biology Yuan, D., Liu, Z., Kaindl, J., Maeda, S., Zhao, J., Sun, X., Xu, J., Gmeiner, P., Wang, H., Kobilka, B. K. 2020


    The alpha2 adrenergic receptors (alpha2ARs) are G protein-coupled receptors (GPCRs) that respond to adrenaline and noradrenaline and couple to the Gi/o family of G proteins. alpha2ARs play important roles in regulating the sympathetic nervous system. Dexmedetomidine is a highly selective alpha2AR agonist used in post-operative patients as an anxiety-reducing, sedative medicine that decreases the requirement for opioids. As is typical for selective alphaAR agonists, dexmedetomidine consists of an imidazole ring and a substituted benzene moiety lacking polar groups, which is in contrast to betaAR-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 alpha2BAR in complex with dexmedetomidine and Go at a resolution of 2.9A by single-particle cryo-EM. The structure reveals the mechanism of alpha2AR-selective activation and provides insights into Gi/o coupling specificity.

    View details for DOI 10.1038/s41589-020-0492-2

    View details for PubMedID 32152538

  • Binding pathway determines norepinephrine selectivity for the human β1AR over β2AR. Cell research Xu, X. n., Kaindl, J. n., Clark, M. J., Hübner, H. n., Hirata, K. n., Sunahara, R. K., Gmeiner, P. n., Kobilka, B. K., Liu, X. n. 2020


    Beta adrenergic receptors (βARs) mediate physiologic responses to the catecholamines epinephrine and norepinephrine released by the sympathetic nervous system. While the hormone epinephrine binds β1AR and β2AR with similar affinity, the smaller neurotransmitter norepinephrine is approximately tenfold selective for the β1AR. To understand the structural basis for this physiologically important selectivity, we solved the crystal structures of the human β1AR 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 β1AR and β2AR, 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.

    View details for DOI 10.1038/s41422-020-00424-2

    View details for PubMedID 33093660

  • Structure of the neurotensin receptor 1 in complex with β-arrestin 1. Nature Huang, W. n., Masureel, M. n., Qianhui, Q. n., Janetzko, J. n., Inoue, A. n., Kato, H. E., Robertson, M. J., Nguyen, K. C., Glenn, J. S., Skiniotis, G. n., Kobilka, B. K. 2020


    Arrestin proteins bind to active, phosphorylated G-protein-coupled receptors (GPCRs), thereby preventing G-protein coupling, triggering receptor internalization, and affecting various downstream signalling pathways1,2. Although there is a wealth of structural information delineating the interactions between GPCRs and G proteins, less is known about how arrestins engage GPCRs. Here we report a cryo-EM structure of full-length human neurotensin receptor 1 (NTSR1) in complex with truncated human β-arrestin 1 (βarr1ΔCT). We found that phosphorylation of NTSR1 was critical for obtaining a stable complex with βarr1ΔCT, and identified phosphorylated sites in both the third intracellular loop and the C terminus that may promote this interaction. In addition, we observed a phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) molecule forming a bridge between the membrane side of NTSR1 transmembrane segments 1 and 4 and the C-lobe of arrestin. Compared to a structure of rhodopsin-arrestin-1, our structure displays an approximately 85° rotation of arrestin relative to the receptor. These findings highlight both conserved aspects but also the plasticity of arrestin-receptor interactions.

    View details for DOI 10.1038/s41586-020-1953-1

    View details for PubMedID 31945771

  • Structures of Gα Proteins in Complex with Their Chaperone Reveal Quality Control Mechanisms. Cell reports Seven, A. B., Hilger, D. n., Papasergi-Scott, M. M., Zhang, L. n., Qu, Q. n., Kobilka, B. K., Tall, G. G., Skiniotis, G. n. 2020


    Many chaperones promote nascent polypeptide folding followed by substrate release through ATP-dependent conformational changes. Here we show cryoEM structures of Gα subunit folding intermediates in complex with full-length Ric-8A, a unique chaperone-client system in which substrate release is facilitated by guanine nucleotide binding to the client G protein. The structures of Ric-8A-Gαi and Ric-8A-Gαq complexes reveal that the chaperone employs its extended C-terminal region to cradle the Ras-like domain of Gα, positioning the Ras core in contact with the Ric-8A core while engaging its switch2 nucleotide binding region. The C-terminal α5 helix of Gα is held away from the Ras-like domain through Ric-8A core domain interactions, which critically depend on recognition of the Gα C terminus by the chaperone. The structures, complemented with biochemical and cellular chaperoning data, support a folding quality control mechanism that ensures proper formation of the C-terminal α5 helix before allowing GTP-gated release of Gα from Ric-8A.

    View details for DOI 10.1016/j.celrep.2020.02.086

    View details for PubMedID 32126208

  • Structural insights into differences in G protein activation by family A and family B GPCRs. Science (New York, N.Y.) Hilger, D. n., Kumar, K. K., Hu, H. n., Pedersen, M. F., O'Brien, E. S., Giehm, L. n., Jennings, C. n., Eskici, G. n., Inoue, A. n., Lerch, M. n., Mathiesen, J. M., Skiniotis, G. n., Kobilka, B. K. 2020; 369 (6503)


    Family B heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) play important roles in carbohydrate metabolism. Recent structures of family B GPCR-Gs protein complexes reveal a disruption in the α-helix of transmembrane segment 6 (TM6) not observed in family A GPCRs. To investigate the functional impact of this structural difference, we compared the structure and function of the glucagon receptor (GCGR; family B) with the β2 adrenergic receptor (β2AR; family A). We determined the structure of the GCGR-Gs complex by means of cryo-electron microscopy at 3.1-angstrom resolution. This structure shows the distinct break in TM6. Guanosine triphosphate (GTP) turnover, guanosine diphosphate release, GTP binding, and G protein dissociation studies revealed much slower rates for G protein activation by the GCGR compared with the β2AR. Fluorescence and double electron-electron resonance studies suggest that this difference is due to the inability of agonist alone to induce a detectable outward movement of the cytoplasmic end of TM6.

    View details for DOI 10.1126/science.aba3373

    View details for PubMedID 32732395

  • Structure and selectivity engineering of the M1 muscarinic receptor toxin complex. Science (New York, N.Y.) Maeda, S. n., Xu, J. n., N Kadji, F. M., Clark, M. J., Zhao, J. n., Tsutsumi, N. n., Aoki, J. n., Sunahara, R. K., Inoue, A. n., Garcia, K. C., Kobilka, B. K. 2020; 369 (6500): 161–67


    Muscarinic toxins (MTs) are natural toxins produced by mamba snakes that primarily bind to muscarinic acetylcholine receptors (MAChRs) and modulate their function. Despite their similar primary and tertiary structures, MTs show distinct binding selectivity toward different MAChRs. The molecular details of how MTs distinguish MAChRs are not well understood. Here, we present the crystal structure of M1AChR in complex with MT7, a subtype-selective anti-M1AChR snake venom toxin. The structure reveals the molecular basis of the extreme subtype specificity of MT7 for M1AChR and the mechanism by which it regulates receptor function. Through in vitro engineering of MT7 finger regions that was guided by the structure, we have converted the selectivity from M1AChR toward M2AChR, suggesting that the three-finger fold is a promising scaffold for developing G protein-coupled receptor modulators.

    View details for DOI 10.1126/science.aax2517

    View details for PubMedID 32646996

  • Conformational transitions of a neurotensin receptor1-Gi1complex. Nature Kato, H. E., Zhang, Y., Hu, H., Suomivuori, C., Kadji, F. M., Aoki, J., Krishna Kumar, K., Fonseca, R., Hilger, D., Huang, W., Latorraca, N. R., Inoue, A., Dror, R. O., Kobilka, B. K., Skiniotis, G. 2019


    Neurotensin receptor1 (NTSR1) is a G-protein-coupled receptor (GPCR) that engages multiple subtypes of G protein, and is involved in the regulation of blood pressure, body temperature, weight and the response to pain. Here we present structures of human NTSR1 in complex with the agonist JMV449 and the heterotrimeric Gi1 protein, at a resolution of 3A. We identify two conformations: a canonical-state complex that is similar to recently reported GPCR-Gi/o complexes (in which the nucleotide-binding pocket adopts moreflexible conformations that may facilitate nucleotide exchange), and a non-canonical state in which the G protein is rotated by about 45degrees relative to the receptor and exhibits a more rigid nucleotide-binding pocket. In the non-canonical state, NTSR1 exhibits features of both active and inactive conformations, which suggests that the structure may represent an intermediate form along the activation pathway of G proteins. This structural information, complemented by molecular dynamics simulations and functional studies, provides insights into the complex process of G-protein activation.

    View details for DOI 10.1038/s41586-019-1337-6

    View details for PubMedID 31243364

  • Assembly of a GPCR-G Protein Complex CELL Du, Y., Duc, N., Rasmussen, S. F., Hilger, D., Kubiak, X., Wang, L., Bohon, J., Kim, H., Wegrecki, M., Asuru, A., Jeong, K., Lee, J., Chance, M. R., Lodowski, D. T., Kobilka, B. K., Chung, K. 2019; 177 (5): 1232-+
  • Structural Insights into the Process of GPCR-G Protein Complex Formation CELL Liu, X., Xu, X., Hilger, D., Aschauer, P., Tiemann, J. S., Du, Y., Liu, H., Hirata, K., Sun, X., Guixa-Gonzalez, R., Mathiesen, J. M., Hildebrand, P. W., Kobilka, B. K. 2019; 177 (5): 1243-+
  • Structures of the M1 and M2 muscarinic acetylcholine receptor/G-protein complexes SCIENCE Maeda, S., Qu, Q., Robertson, M. J., Skiniotis, G., Kobilka, B. K. 2019; 364 (6440): 552-+
  • Selective modulation of the cannabinoid type 1 (CB1) receptor as an emerging platform for the treatment of neuropathic pain MEDCHEMCOMM Banister, S. D., Kumar, K., Kumar, V., Kobilka, B. K., Malhotra, S. V. 2019; 10 (5): 647–59

    View details for DOI 10.1039/c8md00595h

    View details for Web of Science ID 000468790800002

  • Structural insights into the activation of metabotropic glutamate receptors (vol 566, pg 79, 2019) NATURE Koehl, A., Hu, H., Feng, D., Sun, B., Zhang, Y., Robertson, M. J., Chu, M., Kobilka, T., Laeremans, T., Steyaert, J., Tarrasch, J., Dutta, S., Fonseca, R., Weis, W. I., Mathiesen, J. M., Skiniotis, G., Kobilka, B. K. 2019; 567 (7747): E10
  • Diverse GPCRs exhibit conserved water networks for stabilization and activation PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Venkatakrishnan, A. J., Ma, A. K., Fonseca, R., Latorraca, N. R., Kelly, B., Betz, R. M., Asawa, C., Kobilka, B. K., Dror, R. O. 2019; 116 (8): 3288–93
  • Structural Insights into the Subtype-Selective Antagonist Binding to the M2 Muscarinic Receptor Lee, S., Ryoji, S., Shoji, M., Kobayashi, T., Kobilka, B. K., Vaidehi, N. CELL PRESS. 2019: 206A
  • Structure of a Signaling Cannabinoid Receptor 1-G Protein Complex CELL Kumar, K., Shalev-Benami, M., Robertson, M. J., Hu, H., Banister, S. D., Hollingsworth, S. A., Latorraca, N. R., Kato, H. E., Hilger, D., Maeda, S., Weis, W. I., Farrens, D. L., Dror, R. O., Malhotra, S. V., Kobilka, B. K., Skiniotis, G. 2019; 176 (3): 448-+
  • An improved yeast surface display platform for the screening of nanobody immune libraries. Scientific reports Uchanski, T., Zogg, T., Yin, J., Yuan, D., Wohlkonig, A., Fischer, B., Rosenbaum, D. M., Kobilka, B. K., Pardon, E., Steyaert, J. 2019; 9 (1): 382


    Fusions to the C-terminal end of the Aga2p mating adhesion of Saccharomyces cerevisiae have been used in many studies for the selection of affinity reagents by yeast display followed by flow cytometric analysis. Here we present an improved yeast display system for the screening of Nanobody immune libraries where we fused the Nanobody to the N-terminal end of Aga2p to avoid steric hindrance between the fused Nanobody and the antigen. Moreover, the display level of a cloned Nanobody on the surface of an individual yeast cell can be monitored through a covalent fluorophore that is attached in a single enzymatic step to an orthogonal acyl carrier protein (ACP). Additionally, the displayed Nanobody can be easily released from the yeast surface and immobilised on solid surfaces for rapid analysis. To prove the generic nature of this novel Nanobody discovery platform, we conveniently selected Nanobodies against three different antigens, including two membrane proteins.

    View details for PubMedID 30674983

  • Angiotensin Analogs with Divergent Bias Stabilize Distinct Receptor Conformations. Cell Wingler, L. M., Elgeti, M., Hilger, D., Latorraca, N. R., Lerch, M. T., Staus, D. P., Dror, R. O., Kobilka, B. K., Hubbell, W. L., Lefkowitz, R. J. 2019


    "Biased" G protein-coupled receptor (GPCR) agonists preferentially activate pathways mediated by G proteins or beta-arrestins. Here, we use double electron-electron resonance spectroscopy to probe the changes that ligands induce in the conformational distribution of the angiotensin II type I receptor. Monitoring distances between 10 pairs of nitroxide labels distributed across the intracellular regions enabled mapping of four underlying sets of conformations. Ligands from different functional classes have distinct, characteristic effects on the conformational heterogeneity of the receptor. Compared to angiotensin II, the endogenous agonist, agonists with enhanced Gq coupling more strongly stabilize an "open" conformation with an accessible transducer-binding site. beta-arrestin-biased agonists deficient in Gq coupling do not stabilize this open conformation but instead favor two more occluded conformations. These data suggest a structural mechanism for biased ligand action at the angiotensin receptor that can be exploited to rationally design GPCR-targeting drugs with greater specificity of action.

    View details for PubMedID 30639099

  • Mechanism of β2AR regulation by an intracellular positive allosteric modulator. Science (New York, N.Y.) Liu, X. n., Masoudi, A. n., Kahsai, A. W., Huang, L. Y., Pani, B. n., Staus, D. P., Shim, P. J., Hirata, K. n., Simhal, R. K., Schwalb, A. M., Rambarat, P. K., Ahn, S. n., Lefkowitz, R. J., Kobilka, B. n. 2019; 364 (6447): 1283–87


    Drugs targeting the orthosteric, primary binding site of G protein-coupled receptors are the most common therapeutics. Allosteric binding sites, elsewhere on the receptors, are less well-defined, and so less exploited clinically. We report the crystal structure of the prototypic β2-adrenergic receptor in complex with an orthosteric agonist and compound-6FA, a positive allosteric modulator of this receptor. It binds on the receptor's inner surface in a pocket created by intracellular loop 2 and transmembrane segments 3 and 4, stabilizing the loop in an α-helical conformation required to engage the G protein. Structural comparison explains the selectivity of the compound for β2- over the β1-adrenergic receptor. Diversity in location, mechanism, and selectivity of allosteric ligands provides potential to expand the range of receptor drugs.

    View details for DOI 10.1126/science.aaw8981

    View details for PubMedID 31249059