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Doxorubicin (Doxo)-associated cardio-and vasotoxicity has been recognised as a serious complication of cancer chemotherapy. The purpose of this novel paper was to determine the effect of Doxo on G-protein coupled receptor (GPCR)-mediated vasocontraction located on vascular smooth muscle cells. Rat left anterior descending artery segments were incubated for 24 h with 0.5 µM Doxo. The vasocontractile responses by activation of endothelin receptor type A (ETA) and type B (ETB), serotonin receptor 1B (5-HT1B) and thromboxane A2 prostanoid receptor (TP) were investigated by a sensitive myography using specific agonists, while the specificity of the GPCR agonists was verified by applying selective antagonists (i.e. ETA and ETB agonist = 10− 14-10− 7.5 M endothelin-1 (ET-1); ETA antagonist = 10 µM BQ123; ETB agonists = 10− 14-10− 7.5 M sarafotoxin 6c (S6c) and ET-1; ETB antagonist = 0.1 µM BQ788; 5-HT1B agonist = 10− 12-10− 5.5 M 5-carboxamidotryptamine (5-CT); 5-HT1B antagonist = 1 µM GR55562; TP agonist = 10− 12-10− 6.5 M U46619; TP antagonist = 1 µM Seratrodast). Our results show that 0.5 µM Doxo incubation of LAD segments leads to an increased VSMC vasocontraction through the ETB, 5-HT1B and TP GPCRs, with a 2.2-fold increase in ETB-mediated vasocontraction at 10− 10.5 M S6c, a 2.0-fold increase in 5-HT1B-mediated vasocontraction at 10− 5.5 M 5-CT, and a 1.3-fold increase in TP-mediated vasocontraction at 10− 6.5 M U46619. Further studies unravelling the involvement of intracellular GPCR signalling pathways will broaden our understanding of the Doxo-induced vasotoxicity, and thus pave the way to mitigate the adverse effects by potential implementation of adjunct therapy options. [ABSTRACT FROM AUTHOR]

For many deaf signers, a signed language is their first or preferred language; spoken or written languages are often second languages and literacy levels among deaf signers vary. Historically, surveys carried out with deaf signers have been in written form, which means that findings of such studies may be problematic in terms of whether participants are a representative sample (as only those with higher levels of literacy may respond) and in terms of the integrity of the responses (if respondents did not fully understand questions). This paper therefore discusses issues faced in conducting survey research with deaf signers, given that they may face challenges in accessing questionnaires in written form. The paper also discusses how to conduct a multi-country study with deaf signers when they do not have a common sign language by designing a questionnaire using International Sign. We present a case study of the Insign project, which employed an online survey methodology that allowed 84 deaf respondents from 22 different countries to view questions in International Sign about their experiences with existing communication technologies and their expectations of service provision to access European Institutions. We explore the advantages and disadvantages of such an approach in relation to the use of International Sign, challenges in recruiting enough respondents, the time needed to create a signed questionnaire instrument, and how to enable deaf participants to respond in sign language. We conclude with recommendations for social science researchers to consider when administering surveys with deaf signing communities. [ABSTRACT FROM AUTHOR]

It has long been recognised that deaf people experience barriers to political participation and that notions of citizenship do not take into account the needs of deaf sign language users. In light of an effort at the European level to increase the potential for deaf sign language users to participate in political processes through technology, this paper provides results from a survey study of deaf sign language users across Europe as to their preferences in using Telecommunications Relay Services (TRS), whether they would like to see the establishment of a pan-European multilingual TRS and if they would make use of such a service for the purposes of political participation. Responses from 74 deaf people across 14 European member states confirm that deaf people want to see such a service, and would be willing to use it in order to make contact with European institutions. Therefore, the establishment of such a service has the potential to contribute to improved access to, and increased willingness to engage in, democracy through telecommunications and thus enhance the citizenship status of deaf Europeans, and therefore enhance their political participation and access to information and communication in society. [ABSTRACT FROM AUTHOR]

G-protein-coupled receptors (GPCRs) form the largest class of membrane proteins and are an important target for therapeutic drugs. These receptors are highly dynamic proteins sampling a range of conformational states in order to fulfil their complex signalling roles. In order to fully understand GPCR signalling mechanisms it is necessary to extract the receptor protein out of the plasma membrane. Historically this has universally required detergents which inadvertently strip away the annulus of lipid in close association with the receptor and disrupt lateral pressure exerted by the bilayer. Detergent-solubilized GPCRs are very unstable which presents a serious hurdle to characterization by biophysical methods. A range of strategies have been developed to ameliorate the detrimental effect of removing the receptor from the membrane including amphipols and reconstitution into nanodics stabilized by membrane scaffolding proteins (MSPs) but they all require exposure to detergent. Poly(styrene-co-maleic acid) (SMA) incorporates into membranes and spontaneously forms nanoscale poly(styrene-co-maleic acid) lipid particles (SMALPs), effectively acting like a 'molecular pastry cutter' to 'solubilize' GPCRs in the complete absence of detergent at any stage and with preservation of the native annular lipid throughout the process. GPCR-SMALPs have similar pharmacological properties to membrane-bound receptor, exhibit enhanced stability compared with detergent-solubilized receptors and being non-proteinaceous in nature, are fully compatible with downstream biophysical analysis of the encapsulated GPCR. [ABSTRACT FROM AUTHOR]

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In the past few years there has been a growth in the use of nanoparticles for stabilizing lipid membranes that contain embedded proteins. These bionanoparticles provide a solution to the challenging problem of membrane protein isolation by maintaining a lipid bilayer essential to protein integrity and activity. We have previously described the use of an amphipathic polymer (poly(styrene-co-maleic acid), SMA) to produce discoidal nanoparticles with a lipid bilayer core containing the embedded protein. However the structure of the nanoparticle itself has not yet been determined. This leaves a major gap in understanding how the SMA stabilizes the encapsulated bilayer and how the bilayer relates physically and structurally to an unencapsulated lipid bilayer. In this paper we address this issue by describing the structure of the SMA lipid particle (SMALP) using data from small angle neutron scattering (SANS), electron microscopy (EM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC) and nuclear magnetic resonance spectroscopy (NMR). We show that the particle is disc shaped containing a polymer 'bracelet' encircling the lipid bilayer. The structure and orientation of the individual components within the bilayer and polymer are determined showing that styrene moieties within SMA intercalate between the lipid acyl chains. The dimensions of the encapsulated bilayer are also determined and match those measured for a natural membrane. Taken together, the description of the structure of the SMALP forms the foundation for future development and applications of SMALPs in membrane protein production and analysis. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

G-protein coupled receptors (GPCRs) constitute the largest class of membrane proteins and are a major drug target. A serious obstacle to studying GPCR structure/function characteristics is the requirement to extract the receptors from their native environment in the plasma membrane, coupled with the inherent instability of GPCRs in the detergents required for their solubilization. In the present study, we report the first solubilization and purification of a functional GPCR [human adenosine A2A receptor (A2AR)], in the total absence of detergent at any stage, by exploiting spontaneous encapsulation by styrene maleic acid (SMA) co-polymer direct from the membrane into a nanoscale SMA lipid particle (SMALP). Furthermore, the A2AR-SMALP, generated from yeast (Pichia pastoris) or mammalian cells, exhibited increased thermostability (~5°C) compared with detergent [DDM (n-dodecyl-β-D-maltopyranoside)]-solubilized A2AR controls. The A2AR-SMALP was also stable when stored for prolonged periods at 4 °C and was resistant to multiple freeze-thaw cycles, in marked contrast with the detergent-solubilized receptor. These properties establish the potential for using GPCR-SMALP in receptor-based drug discovery assays. Moreover, in contrast with nanodiscs stabilized by scaffold proteins, the non-proteinaceous nature of the SMA polymer allowed unobscured biophysical characterization of the embedded receptor. Consequently, CD spectroscopy was used to relate changes in secondary structure to loss of ligand binding ([3H]ZM241385) capability. SMALP-solubilization of GPCRs, retaining the annular lipid environment, will enable a wide range of therapeutic targets to be prepared in native-like state to aid drug discovery and understanding of GPCR molecular mechanisms. [ABSTRACT FROM AUTHOR]

The CGRP (calcitonin gene-related peptide) receptor is a family B GPCR (G-protein-coupled receptor). It consists of a GPCR, CLR (calcitonin receptor-like receptor) and an accessory protein, RAMP1 (receptor activity modifying protein 1). RAMP1 is needed for CGRP binding and also cell-surface expression of CLR. CLR is an example of a family B GPCR. Unlike family A GPCRs, little is known about how these receptors are activated by their endogenous ligands. This review considers what is known about the activation of family B GPCRs and then considers how this might be applied to CLR, particularly in light of new knowledge of the crystal structures of family A GPCRs. [ABSTRACT FROM AUTHOR]

The CGRP (calcitonin gene-related peptide) receptor is a family B GPCR (G-protein-coupled receptor). It consists of a GPCR, CLR (calcitonin receptor-like receptor) and an accessory protein, RAMP1 (receptor activity-modifying protein 1). RAMP1 is needed for CGRP binding and also cell-surface expression of CLR. There have been few systematic studies of the ECLs (extracellular loops) of family B GPCRs. However, they are likely to be especially important for the interaction of the N-termini of the peptide agonists that are the natural agonists for these receptors. We have carried out alanine scans on all three ECLs of CLR, as well as their associated juxtamembrane regions. Residues within all three loops influence CGRP binding and receptor activation. Mutation of Ala203 and Ala206 on ECL1 to leucine increased the affinity of CGRP. Residues at the top of TM (transmembrane) helices 2 and 3 influenced CGRP binding and receptor activation. L351A and E357A in TM6/ECL3 reduced receptor expression and may be needed for CLR association with RAMP1. ECL2 seems especially important for CLR function; of the 16 residues so far examined in this loop, eight residues reduce the potency of CGRP at stimulating cAMP production when mutated to alanine. [ABSTRACT FROM AUTHOR]

In order to study the structure and function of a protein, it is generally required that the protein in question is purified away from all others. For soluble proteins, this process is greatly aided by the lack of any restriction on the free and independent diffusion of individual protein particles in three dimensions. This is not the case for membrane proteins, as the membrane itself forms a continuum that joins the proteins within the membrane with one another. It is therefore essential that the membrane is disrupted in order to allow separation and hence purification of membrane proteins. In the present review, we examine recent advances in the methods employed to separate membrane proteins before purification. These approaches move away from solubilization methods based on the use of small surfactants, which have been shown to suffer from significant practical problems. Instead, the present review focuses on methods that stem from the field of nanotechnology and use a range of reagents that fragment the membrane into nanometre-scale particles containing the protein complete with the local membrane environment. In particular, we examine a method employing the amphipathic polymer poly(styrene-co-maleic acid), which is able to reversibly encapsulate the membrane protein in a 10 nm disc-like structure ideally suited to purification and further biochemical study. [ABSTRACT FROM AUTHOR]

BACKGROUND: Clinicians use fibrosis in a liver biopsy to predict clinical outcomes of chronic liver disease. The performance of non-invasive tests has been evaluated against histological assessment of fibrosis but use of clinical outcomes as the reference standard would be ideal. The enhanced liver fibrosis (ELF) test was derived and validated in a large cohort of patients and shown to have high diagnostic accuracy (area under the curve (AUC)=0.80 95% CI 0.76 to 0.85) in identification of significant fibrosis on biopsy. OBJECTIVE: To evaluate ELF performance in predicting clinical outcomes by following up the original ELF cohort. METHODS: Patients recruited to the ELF study at seven English centres were followed up for liver morbidity and mortality by examination of clinical data. Defaulting/discharged patients were followed up by family practitioner questionnaires. Primary outcome measure was liver-related morbidity/liver-related death. RESULTS: 457 patients were followed up (median 7 years), with ascertainment of clinical status in 92%. There were 61 liver-related outcomes (39 deaths). Survival analysis showed that the ELF score predicts liver outcomes, with people having the highest ELF scores being significantly more likely to have clinical outcomes than those in lower-score groups. A Cox proportional hazards model showed fully adjusted HRs of 75 (ELF score 12.52–16.67), 20 (10.426–12.51) and 5 (8.34–10.425) compared with patients with ELF <8.34. A unit change in ELF is associated with a doubling of risk of liver-related outcome. CONCLUSIONS: An ELF test can predict clinical outcomes in patients with chronic liver disease and may be a useful prognostic tool in clinical practice. [ABSTRACT FROM AUTHOR]

Abstract: Non-peptide antagonists of the oxytocin receptor (OTR) have been developed to prevent pre-term labour. The benzoxazinone-based antagonists L-371,257 and L-372,662 display pronounced species-dependent pharmacology with respect to selectivity for the OTR over the V1a vasopressin receptor. Examination of receptor sequences from different species identified Ala318 in helix 7 of the human OTR as a candidate discriminator required for high affinity binding. The mutant receptor [A318G]OTR was engineered and characterised using ligands representing many different chemical classes. Of all the ligands investigated, only the benzoxazinone-based antagonists had decreased affinity for [A318G]OTR. Molecular modelling revealed that Ala318 provides a direct hydrophobic contact with a methoxy group of L-371,257 and L-372,662. [Copyright &y& Elsevier]

Defining how the agonist–receptor interaction differs from that of the antagonist–receptor and understanding the mechanisms of receptor activation are fundamental issues in cell signalling. The V1a vasopressin receptor (V1aR) is a member of a family of related G-protein coupled receptors that are activated by neurohypophysial peptide hormones, including vasopressin (AVP). It has recently been reported that an arginyl in the distal N-terminus of the V1aR is critical for binding agonists but not antagonists. To determine specific features required at this locus to support high affinity agonist binding and second messenger generation, Arg46 was substituted by all other 19 encoded amino acids. Our data establish that there is an absolute requirement for arginyl, as none of the [R46X]V1aR mutant constructs supported high affinity agonist binding and all 19 had defective signalling. In contrast, all of the mutant receptors possessed wildtype binding for both peptide and nonpeptide antagonists. The ratio of Ki to EC50, an indicator of efficacy, was increased for all substitutions. Consequently, although [R46X]V1aR constructs have a lower affinity for agonist, once AVP has bound all 19 are more likely than the wildtype V1aR to become activated. Therefore, in the wildtype V1aR, Arg46 constrains the inactive conformation of the receptor. On binding AVP this constraint is alleviated, promoting the transition to active V1aR. Our findings explain why arginyl is conserved at this locus throughout the evolutionary lineage of the neurohypophysial peptide hormone receptor family of G-protein coupled receptors. [ABSTRACT FROM AUTHOR]

Total retro-inverso (TRI) analogues of bradykinin (BK), the Ba-selective kinin antagonist d-Arg[Hyp,d-Phe,Leu]BK, angiotensin II (AT II) and the AT II antagonist Saralasin ([Sar,Val,Ala]AT II) were prepared by conventional solid-phase synthesis. Molecular recognition of TRI peptidomimetics by G-protein-coupled receptors was studied by competitive radioligand displacement experiments. TRI analogues of d-Arg[Hyp,d-Phe,Leu]BK specifically bound to the kidney medulla Ba bradykinin receptor with affinities (K) ranging from 64 μM to 4 μM. Conversely, TRI analogues of BK, AT II and Saralasin did not bind to either the B bradykinin receptor or the rat AT AT II receptor, respectively. These studies indicate that the TRI strategy is more compatible with the synthesis of antagonists than 'agonists'. Three TRI peptidomimetics of d-Arg[Hyp,d-Phe,Leu]BK were weak inhibitors of angiotensin converting enzyme. All other TRI peptidomimetics had no effect upon ACE activity. These data endorse the utility of the TRI strategy for the synthesis of protease-resistant antagonists of peptide hormones and neuropeptides. [ABSTRACT FROM AUTHOR]

Total retro-inverso (TRI) analogues of bradykinin (BK), the B-selective kinin antagonist d-Arg[Hyp, d-Phe,Leu]BK, angiotensin II (AT II) and the AT II antagonist Saralasin ([Sar, Val, Ala]AT II) were prepared by conventional solid-phase synthesis. Molecular recognition of TRI peptidomimetics by G-protein-coupled receptors was studied by competitive radioligand displacement experiments. TRI analogues of d-Arg[Hyp, d-Phe,Leu]BK specifically bound to the kidney medulla B bradykinin receptor with affinities (K) ranging from 64 μM to 4 μM. Conversely, TRI analogues of BK, AT II and Saralasin did not bind to either the B bradykinin receptor or the rat ATAT II receptor, respectively. These studies indicate that the TRI strategy is more compatible with the synthesis of antagonists than 'agonists'. Three TRI peptidomimetics of d-Arg[Hyp, d-Phe,Leu]BK were weak inhibitors of angiotensin converting enzyme. All other TRI peptidomimetics had no effect upon ACE activity. These data endorse the utility of the TRI strategy for the synthesis of protease-resistant antagonists of peptide hormones and neuropeptides. [ABSTRACT FROM AUTHOR]

The papers resulting from the recent Biochemical Society Focused Meeting 'G-Protein-Coupled Receptors: from Structural Insights to Functional Mechanisms' held in Prato in September 2012 are introduced in the present overview. A number of future goals for GPCR (G-protein-coupled receptor) research are considered, including the need to develop biophysical and computational methods to explore the full range of GPCR conformations and their dynamics, the need to develop methods to take this into account for drug discovery and the importance of relating observations on isolated receptors or receptors expressed in model systems to receptor function in vivo. [ABSTRACT FROM AUTHOR]