XFEL structures of the human MT2 melatonin receptor reveal the basis of subtype selectivity

The human MT1 and MT2 melatonin receptors1,2 are G-protein-coupled receptors (GPCRs) that help to regulate circadian rhythm and sleep patterns3. Drug development efforts have targeted both receptors for the treatment of insomnia, circadian rhythm and mood disorders, and cancer3, and MT2 has also been implicated in type 2 diabetes4,5. Here we report X-ray free electron laser (XFEL) structures of the human MT2 receptor in complex with the agonists 2-phenylmelatonin (2-PMT) and ramelteon6 at resolutions of 2.8 Å and 3.3 Å, respectively, along with two structures of function-related mutants: H2085.46A (superscripts represent the Ballesteros–Weinstein residue numbering nomenclature7) and N862.50D, obtained in complex with 2-PMT. Comparison of the structures of MT2 with a published structure8 of MT1 reveals that, despite conservation of the orthosteric ligand-binding site residues, there are notable conformational variations as well as differences in [3H]melatonin dissociation kinetics that provide insights into the selectivity between melatonin receptor subtypes. A membrane-buried lateral ligand entry channel is observed in both MT1 and MT2, but in addition the MT2 structures reveal a narrow opening towards the solvent in the extracellular part of the receptor. We provide functional and kinetic data that support a prominent role for intramembrane ligand entry in both receptors, and suggest that there might also be an extracellular entry path in MT2. Our findings contribute to a molecular understanding of melatonin receptor subtype selectivity and ligand access modes, which are essential for the design of highly selective melatonin tool compounds and therapeutic agents. © 2019, The Author(s), under exclusive licence to Springer Nature Limited

Structural basis of ligand recognition at the human MT1 melatonin receptor

Melatonin (N-acetyl-5-methoxytryptamine) is a neurohormone that maintains circadian rhythms1 by synchronization to environmental cues and is involved in diverse physiological processes2 such as the regulation of blood pressure and core body temperature, oncogenesis, and immune function3. Melatonin is formed in the pineal gland in a light-regulated manner4 by enzymatic conversion from 5-hydroxytryptamine (5-HT or serotonin), and modulates sleep and wakefulness5 by activating two high-affinity G-protein-coupled receptors, type 1A (MT1) and type 1B (MT2)3,6. Shift work, travel, and ubiquitous artificial lighting can disrupt natural circadian rhythms; as a result, sleep disorders affect a substantial population in modern society and pose a considerable economic burden7. Over-the-counter melatonin is widely used to alleviate jet lag and as a safer alternative to benzodiazepines and other sleeping aids8,9, and is one of the most popular supplements in the United States10. Here, we present high-resolution room-temperature X-ray free electron laser (XFEL) structures of MT1 in complex with four agonists: the insomnia drug ramelteon11, two melatonin analogues, and the mixed melatonin–serotonin antidepressant agomelatine12,13. The structure of MT2 is described in an accompanying paper14. Although the MT1 and 5-HT receptors have similar endogenous ligands, and agomelatine acts on both receptors, the receptors differ markedly in the structure and composition of their ligand pockets; in MT1, access to the ligand pocket is tightly sealed from solvent by extracellular loop 2, leaving only a narrow channel between transmembrane helices IV and V that connects it to the lipid bilayer. The binding site is extremely compact, and ligands interact with MT1 mainly by strong aromatic stacking with Phe179 and auxiliary hydrogen bonds with Asn162 and Gln181. Our structures provide an unexpected example of atypical ligand entry for a non-lipid receptor, lay the molecular foundation of ligand recognition by melatonin receptors, and will facilitate the design of future tool compounds and therapeutic agents, while their comparison to 5-HT receptors yields insights into the evolution and polypharmacology of G-protein-coupled receptors

Publisher Correction: Structural basis of ligand recognition at the human MT1 melatonin receptor (Nature, (2019), 569, 7755, (284-288), 10.1038/s41586-019-1141-3)

Change history: In this Letter, the rotation signs around 90°, 135° and 15° were missing and in the HTML, Extended Data Tables 2 and 3 were the wrong tables; these errors have been corrected online. © 2019, The Author(s), under exclusive licence to Springer Nature Limited

People detection and tracking with World-Z map from a single stereo camera

In this paper we propose a new people tracking system that uses a single stereo camera fixed at a high position and observing the scene at an oblique angle. We introduce the notion of world-Z map and show that 3D people detection and segmentation can be performed efficiently in this map and outperforms significantly the methods based on depth or plan-view. Detection and tracking play complementary roles, we derive a probabilistic framework for tracking based on motion. The system successfully deals with very complex situations without loosing track of people in highly cluttered scenes for long observation periods and achieves around 10 fps on a single PC

REFLECTIVITE HEMISPHERIQUE ET DIFFUSE DE COUCHES MINCES DE TUNGSTENE PREPAREES PAR DECOMPOSITION EN PHASE VAPEUR

Sur supports de quartz fondu, par décomposition en phase vapeur (CVD) de l'hexacarbonyle de tungstène W(CO)6, en présence ou non d'oxygène, sont obtenus deux types de matériau en couches minces, appelés respectivement "tungstène noir" (constitué principalement d'oxydes de tungstène) ou "tungstène réflecteur" (composé essentiellement de carbures de tungstène). A partir des mesures, à température ambiante, des pouvoirs réflecteurs hémisphérique, spéculaire et diffus, effectuées entre 0,25 et 15 µm immédiatement après la préparation ou après le recuit dans différentes atmosphères, sont déterminées les caractéristiques de sélectivité des couches. L'évolution de l'état de cristallisation, de la composition et de la rugosité de surface, en fonction des conditions de préparation et de recuit dans les différentes atmosphères, est mise en évidence par des mesures de diffraction de rayons X et de microscopie électronique à balayage.Two kinds of thin films were prepared on fused quartz substrates by chemical vapor decomposition (CVD) of tungsten hexacarbonyle W(CO)6 in the presence or absence of oxygen. One, called "black tungsten", is mainly composed by tungsten oxides, the other, "reflective tungsten", is constituted by tungsten carbide. The caracteristics of selectivity were determined from measurements of hemispherical, diffuse and specular reflectances in the spectral range of 0.25 to 15 µm, immediately after preparation or after annealing in argon, hydrogen or air. The evolution of the crystallinity, composition and surface texture as function of preparation conditions and annealings was shown by XR diffraction patterns and scanning electron micrographs

GPU-based shape silhouettes

In this paper, we present a new method for surface-based shape reconstruction from a set of silhouette images. We propose to project the viewing cones from all viewpoints to the 3D space and compute the intersections that represent the vertices of the Visual Hull (VH). We propose a method for fast traversal of the layers of the projected cones and retrieve the viewing edges that lie to the surface of the VH. Taking advantage of the power of Graphics Processing Units (GPU), the proposed method achieves a real-time full reconstruction of VH rather than rendering a novel view of the VH. The experiments on several data sets, including real data, demonstrate the efficiency of the method for real-time visual hull reconstruction

Synthesis of 2(3H)-benzoxazolone derivatives as potential melatonin receptor ligands

This article reports the synthesis of new 2(3H)-benzoxazolone-based ligands for the melatonin receptors in which an acetamidopropyl side-chain was incorporated. Construction of the acetamidopropyl moiety was achieved via a Wadsworth-Emmons approach. Although these compounds can be seen as derivatives of N-[3-(3-methoxyphenyl)propyl]acetamide (MPPA), which is the exact analogue of melatonin in which the 1,2-indole nitrogen atoms are deleted, they exhibit lower affinities for the melatonin receptors probably due to an unfavourable steric bulk and hydrophilic interactions

Synthesis of N-(4,6-dimethylpyridin-2-yl)-benzoxazolinonyl methylcarboxamides with potential antiinflammatory activity

New aryl(alkyl)carboxamides issued from 2-amino-4,6-dimethylpyridine and benzoxazolinone pharmacophores designed as antiinflammatory agents were synthesized from suitable methyl substituted o-aminophenols

N-[2-(7-methoxy-1-naphthyl)ethyl]acetamide, a Potent Melatonin Analog

The four crystallographically independent molecules present in the unit cell of N-[2-(7-methoxy-1-naphthyl)ethyl]acetamide, C15H17NO2, are very similar; the naphthalene ring is planar, the methoxy substituent is staggered and the side chain is oriented so that the amide and aromatic groups are approximately parallel. This conformation of the longer side chain is different from the fully extended conformation observed in the neurohormone melatonin