Crystal structure of the β2 adrenergic receptor-Gs protein complex

G protein-coupled receptors (GPCRs) are responsible for the majority of cellular responses to hormones and neurotransmitters as well as the senses of sight, olfaction and taste. The paradigm of GPCR signalling is the activation of a heterotrimeric GTP binding protein (G protein) by an agonist-occupied receptor. The β(2) adrenergic receptor (β(2)AR) activation of Gs, the stimulatory G protein for adenylyl cyclase, has long been a model system for GPCR signalling. Here we present the crystal structure of the active state ternary complex composed of agonist-occupied monomeric β(2)AR and nucleotide-free Gs heterotrimer. The principal interactions between the β(2)AR and Gs involve the amino- and carboxy-terminal α-helices of Gs, with conformational changes propagating to the nucleotide-binding pocket. The largest conformational changes in the β(2)AR include a 14 ? outward movement at the cytoplasmic end of transmembrane segment 6 (TM6) and an α-helical extension of the cytoplasmic end of TM5. The most surprising observation is a major displacement of the α-helical domain of Gαs relative to the Ras-like GTPase domain. This crystal structure represents the first high-resolution view of transmembrane signalling by a GPCR.     

Hypotrichosis simplex of the scalp is associated with nonsense mutations in CDSN encoding corneodesmosin

We have identified nonsense mutations in the gene CDSN (encoding corneodesmosin) in three families suffering from hypotrichosis simplex of the scalp (HSS; OMIM 146520). CDSN, a glycoprotein expressed in the epidermis and inner root sheath (IRS) of hair follicles, is a keratinocyte adhesion molecule. Truncated CDSN aggregates were detected in the superficial dermis and at the periphery of hair follicles. Our findings suggest that CDSN is important in normal scalp hair physiology.     

Structure of the human M2 muscarinic acetylcholine receptor bound to an antagonist

The parasympathetic branch of the autonomic nervous system regulates the activity of multiple organ systems. Muscarinic receptors are G-protein-coupled receptors that mediate the response to acetylcholine released from parasympathetic nerves. Their role in the unconscious regulation of organ and central nervous system function makes them potential therapeutic targets for a broad spectrum of diseases. The M2 muscarinic acetylcholine receptor (M2 receptor) is essential for the physiological control of cardiovascular function through activation of G-protein-coupled inwardly rectifying potassium channels, and is of particular interest because of its extensive pharmacological characterization with both orthosteric and allosteric ligands. Here we report the structure of the antagonist-bound human M2 receptor, the first human acetylcholine receptor to be characterized structurally, to our knowledge. The antagonist 3-quinuclidinyl-benzilate binds in the middle of a long aqueous channel extending approximately two-thirds through the membrane. The orthosteric binding pocket is formed by amino acids that are identical in all five muscarinic receptor subtypes, and shares structural homology with other functionally unrelated acetylcholine binding proteins from different species. A layer of tyrosine residues forms an aromatic cap restricting dissociation of the bound ligand. A binding site for allosteric ligands has been mapped to residues at the entrance to the binding pocket near this aromatic cap. The structure of the M2 receptor provides insights into the challenges of developing subtype-selective ligands for muscarinic receptors and their propensity for allosteric regulation.     

Crystal structure of the µ-opioid receptor bound to a morphinan antagonist

Opium is one of the world's oldest drugs, and its derivatives morphine and codeine are among the most used clinical drugs to relieve severe pain. These prototypical opioids produce analgesia as well as many undesirable side effects (sedation, apnoea and dependence) by binding to and activating the G-protein-coupled μ-opioid receptor (μ-OR) in the central nervous system. Here we describe the 2.8?? crystal structure of the mouse μ-OR in complex with an irreversible morphinan antagonist. Compared to the buried binding pocket observed in most G-protein-coupled receptors published so far, the morphinan ligand binds deeply within a large solvent-exposed pocket. Of particular interest, the μ-OR crystallizes as a two-fold symmetrical dimer through a four-helix bundle motif formed by transmembrane segments 5 and 6. These high-resolution insights into opioid receptor structure will enable the application of structure-based approaches to develop better drugs for the management of pain and addiction.     

The J1 glycoprotein--a novel nervous system cell adhesion molecule of the L2/HNK-1 family

The neural cell adhesion molecules L1 and N-CAM share a common carbohydrate epitope that is recognized by the monoclonal antibodies L2 and HNK-1. The L2/HNK-1 epitope is also present on the myelin-associated glycoprotein (MAG) which is thought to mediate surface interactions between the axon and myelinating cell. Other, as yet unidentified, cell-surface glycoproteins are recognized by the two antibodies and are believed to belong to a family of neural cell adhesion molecules. To test this hypothesis, we have prepared polyclonal antibodies to a prominent member of the L2/HNK-1 family, the 160K (relative molecular mass (Mr)160,000) glycoprotein. Here we report that these antibodies, designated J1 antibodies, react with astrocytes and oligodendrocytes and interfere with neurone-astrocyte adhesion, but not with neurone-neurone or astrocyte-astrocyte adhesion. This result suggests the involvement of the J1 antigen in cell-cell interactions.     

Sources of variation in counts of meristic features of Yellowstone cutthroat trout ( Oncorhynchus clarki bouvieri )

We determined variability in counts of meristic features (pyloric caecae, vertebrae, pelvic fin rays, gillrakers, basibranchial teeth, scales above the lateral line, and scales in the lateral series) of Yellowstone cutthroat trout ( Oncorhynchus clarki bouvieri ) by 3 independent readers, by the same reader on 3 different occasions, and among fish from 12 sampling sites within a 650-km 2 watershed. Genetic purity of the cutthroat trout was determined by electrophoretic analysis. Significant differences in meristic counts were observed among 3 readers and among sampling sites, but not among 3 occasions by a single reader. Scale counts were within the reported range for Yellowstone cutthroat trout, but counts of other structures (pyloric caecae, gillrakers, vertebrae) were as similar to rainbow trout as to Yellowstone cutthroat trout. Meristic counts identified the fish as cutthroat trout; however, variation among readers and sampling sites, as well as within the species, limits their use when identifying genetically pure cutthroat trout or assessing possible integration with rainbow trout.     

Effect of theophylline on myocardial adenylate cyclase activity

Summary Theophylline (0.01–10.0 mM) did not incease but rather decreased adenylate cyclase activity (AC) of guineapig auricles. Isoprenaline (1–100 M) and sodium fluoride (0.3–10.0 mM)stimulated AC in aconcentration-dependent manner.This work was supported by the Deutsche Forschungsgemeinschaft. The continous advice of Dr U. Schwabe is gratefully acknowledged.