Identification of a ß-arrestin-biased negative allosteric modulator for the ß2-adrenergic receptor.

Catecholamine-stimulated ß2-adrenergic receptor (ß2AR) signaling via the canonical Gs-adenylyl cyclase-cAMP-PKA pathway regulates numerous physiological functions, including the therapeutic effects of exogenous ß-agonists in the treatment of airway disease. ß2AR signaling is tightly regulated by GRKs and ß-arrestins, which together promote ß2AR desensitization and internalization as well as downstream signaling, often antithetical to the canonical pathway. Thus, the ability to bias ß2AR signaling toward the Gs pathway while avoiding ß-arrestin-mediated effects may provide a strategy to improve the functional consequences of ß2AR activation. Since attempts to develop Gs-biased agonists and allosteric modulators for the ß2AR have been largely unsuccessful, here we screened small molecule libraries for allosteric modulators that selectively inhibit ß-arrestin recruitment to the receptor. This screen identified several compounds that met this profile, and, of these, a difluorophenyl quinazoline (DFPQ) derivative was found to be a selective negative allosteric modulator of ß-arrestin recruitment to the ß2AR while having no effect on ß2AR coupling to Gs. DFPQ effectively inhibits agonist-promoted phosphorylation and internalization of the ß2AR and protects against the functional desensitization of ß-agonist mediated regulation in cell and tissue models. The effects of DFPQ were also specific to the ß2AR with minimal effects on the ß1AR. Modeling, mutagenesis, and medicinal chemistry studies support DFPQ derivatives binding to an intracellular membrane-facing region of the ß2AR, including residues within transmembrane domains 3 and 4 and intracellular loop 2. DFPQ thus represents a class of biased allosteric modulators that targets an allosteric site of the ß2AR.

ß2 -Adrenoceptor agonist profiling reveals biased signalling phenotypes for the ß2 -adrenoceptor with possible implications for the treatment of asthma.

BACKGROUND AND PURPOSE: ß-Adrenoceptor agonists relieve airflow obstruction by activating ß2 -adrenoceptors, which are G protein-coupled receptors (GPCRs) expressed on human airway smooth muscle (HASM) cells. The currently available ß-adrenoceptor agonists are balanced agonists, however, and signal through both the stimulatory G protein (Gs )- and ß-arrestin-mediated pathways. While Gs signalling is beneficial and promotes HASM relaxation, ß-arrestin activation is associated with reduced Gs efficacy. In this context, biased ligands that selectively promote ß2 -adrenoceptor coupling to Gs signalling represent a promising strategy to treat asthma. Here, we examined several ß-adrenoceptor agonists to identify Gs -biased ligands devoid of ß-arrestin-mediated effects. EXPERIMENTAL APPROACH: Gs -biased ligands for the ß2 -adrenoceptor were identified by high-throughput screening and then evaluated for Gs interaction, Gi interaction, cAMP production, ß-arrestin interaction, GPCR kinase (GRK) phosphorylation of the receptor, receptor trafficking, ERK activation, and functional desensitization of the ß2 -adrenoceptor. KEY RESULTS: We identified ractopamine, dobutamine, and higenamine as Gs -biased agonists that activate the Gs /cAMP pathway upon ß2 -adrenoceptor stimulation while showing minimal Gi or ß-arrestin interaction. Furthermore, these compounds did not induce any receptor trafficking and had reduced GRK5-mediated phosphorylation of the ß2 -adrenoceptor. Finally, we observed minimal physiological desensitization of the ß2 -adrenoceptor in primary HASM cells upon treatment with biased agonists. CONCLUSION AND IMPLICATIONS: Our work demonstrates that Gs -biased signalling through the ß2 -adrenoceptor may prove to be an effective strategy to promote HASM relaxation in the treatment of asthma. Such biased compounds may also be useful in identifying the molecular mechanisms that determine biased signalling and in design of safer drugs.

Femoroacetabular translation in female athletes and dancers assessed by dynamic hip ultrasonography.

OBJECTIVE: To compare femoroacetabular (FA) translation between dancers and athletes with hip pain and between dancers with and without hip pain. METHODS: In this cross-sectional study, 171 female athletes and dancers with hip pain underwent dynamic hip ultrasound (DHUS) of FA translation in three positions: neutral (N), neutral with contralateral hip flexion (NF), apprehension position with contralateral hip flexion (EER-F). Multivariable linear regression analysis was used to assess variation in FA translation between dancers and athletes in the presence of age, Beighton score/hypermobility, BMI, radiographic markers of acetabular dysplasia and femoral version angles. Symptomatic dancers were matched to asymptomatic dancer controls on age, height and BMI, and comparison analyses of FA translation were conducted controlling for matched propensity score and Beighton score. RESULTS: In the symptomatic cohort, dancers were younger, had higher Beighton scores and were more hypermobile than non-dancers. Dancers also showed greater NF, EER-F and max US-min US (delta) compared with non-dancers (mean 5.4 mm vs 4.4 mm, p=0.02; mean 6.3 mm vs 5.2 mm, p=0.01; 4.2 mm vs 3.6 mm, p=0.03, respectively). Symptomatic dancers showed greater NF and EER-F compared with asymptomatic dancers (mean 5.5 mm vs 2.9 mm, p<0.001; mean 6.3 mm vs 4.2 mm, p<0.001, respectively). Comparison of symptomatic dancers with and without hip dysplasia showed no difference in DHUS measurements. CONCLUSION: DHUS measurements of FA translation are greater in female dancers with hip pain relative to female non-dancer athletes with hip pain and asymptomatic female dancers.

Measuring cognition in teams: a cross-domain review.

OBJECTIVE: The purpose of this article is twofold: to provide a critical cross-domain evaluation of team cognition measurement options and to provide novice researchers with practical guidance when selecting a measurement method. BACKGROUND: A vast selection of measurement approaches exist for measuring team cognition constructs including team mental models, transactive memory systems, team situation awareness, strategic consensus, and cognitive processes. METHODS: Empirical studies and theoretical articles were reviewed to identify all of the existing approaches for measuring team cognition. These approaches were evaluated based on theoretical perspective assumed, constructs studied, resources required, level of obtrusiveness, internal consistency reliability, and predictive validity. RESULTS: The evaluations suggest that all existing methods are viable options from the point of view of reliability and validity, and that there are potential opportunities for cross-domain use. For example, methods traditionally used only to measure mental models may be useful for examining transactive memory and situation awareness. The selection of team cognition measures requires researchers to answer several key questions regarding the theoretical nature of team cognition and the practical feasibility of each method. CONCLUSIONS: We provide novice researchers with guidance regarding how to begin the search for a team cognition measure and suggest several new ideas regarding future measurement research. APPLICATIONS: We provide (1) a broad overview and evaluation of existing team cognition measurement methods, (2) suggestions for new uses of those methods across research domains, and (3) critical guidance for novice researchers looking to measure team cognition.

Mycobacterium tuberculosis type II NADH-menaquinone oxidoreductase catalyzes electron transfer through a two-site ping-pong mechanism and has two quinone-binding sites.

Type II NADH-quinone oxidoreductase (NDH-2) catalyzes the transfer electrons from NADH to the quinone pool and plays an essential role in the oxidative phosphorylation system of Mycobacterium tuberculosis (Mtb). The absence of NDH-2 in the mammalian mitochondrial electron transport chain makes this enzyme an attractive target for antibiotic development. To fully establish the kinetic properties of this enzyme, we studied the interaction of Mtb NDH-2 with substrates, NADH, and various quinone analogues and their products in both membrane and soluble environments. These studies, and comparative analyses of the kinetics with thio-NAD(+) and quinone electron acceptors, provided evidence that Mtb NDH-2 catalyzes the transfer electrons from NADH to quinone substrates by a nonclassical, two-site ping-pong kinetic mechanism whereby substrate quinones bind to a site that is distinct from the NADH-binding site. Furthermore, the effects of quinols on Mtb NDH-2 catalytic activity demonstrate the presence of two binding sites for quinone ligands, one favoring the reduced form and the other favoring the oxidized form.

Anti-inflammatory compounds parthenolide and Bay 11-7082 are direct inhibitors of the inflammasome.

Activation of the inflammasome generates the pro-inflammatory cytokines interleukin-1 beta and -18, which are important mediators of inflammation. Abnormal activation of the inflammasome leads to many inflammatory diseases, including gout, silicosis, neurodegeneration, and genetically inherited periodic fever syndromes. Therefore, identification of small molecule inhibitors that target the inflammasome is an important step toward developing effective therapeutics for the treatment of inflammation. Here, we show that the herbal NF-kappaB inhibitory compound parthenolide inhibits the activity of multiple inflammasomes in macrophages by directly inhibiting the protease activity of caspase-1. Additional investigations of other NF-kappaB inhibitors revealed that the synthetic I kappaB kinase-beta inhibitor Bay 11-7082 and structurally related vinyl sulfone compounds selectively inhibit NLRP3 inflammasome activity in macrophages independent of their inhibitory effect on NF-kappaB activity. In vitro assays of the effect of parthenolide and Bay 11-7082 on the ATPase activity of NLRP3 demonstrated that both compounds inhibit the ATPase activity of NLRP3, suggesting that the inhibitory effect of these compounds on inflammasome activity could be mediated in part through their effect on the ATPase activity of NLRP3. Our results thus elucidate the molecular mechanism for the therapeutic anti-inflammatory activity of parthenolide and identify vinyl sulfones as a new class of potential therapeutics that target the NLRP3 inflammasome.

Taking the chemical out of chemical genetics.

Screening a library of expressed cyclic peptides identified clones that reverse the cytotoxicity of alpha-synuclein in yeast and Caenorhabditis elegans. The results suggest a new approach for intervention in Parkinson's disease, and perhaps a druggable target.

Effect of rapamycin on mouse chronic lymphocytic leukemia and the development of nonhematopoietic malignancies in Emu-TCL1 transgenic mice.

Chronic lymphocytic leukemia (CLL) is the most common leukemia in the world. The TCL1 gene, responsible for prolymphocytic T cell leukemia, is also overexpressed in human B cell malignancies and overexpression of the Tcl1 protein occurs frequently in CLL. Aging transgenic mice that overexpress TCL1 under control of the mu immunoglobulin gene enhancer, develop a CD5+ B cell lymphoproliferative disorder mimicking human CLL and implicating TCL1 in the pathogenesis of CLL. In the current study, we exploited this transgenic mouse to investigate two different CLL-related issues: potential treatment of CLL and characterization of neoplasms that accompany CLL. We successfully transplanted CLL cells into syngeneic mice that led to CLL development in the recipient mice. This approach allowed us to verify the involvement of the Tcl1/Akt/mTOR biochemical pathway in the disease by testing the ability of a specific pharmacologic agent, rapamycin, to slow CLL. We also showed that 36% of these transgenic mice were affected by solid malignancies, in which the expression of the Tcl1 protein was absent. These findings indicate that other oncogenic mechanism(s) may be involved in the development of solid tumors in Emu-TCL1 transgenic mice.

A comprehensive model for the allosteric regulation of mammalian ribonucleotide reductase. Functional consequences of ATP- and dATP-induced oligomerization of the large subunit.

Reduction of NDPs by murine ribonucleotide reductase (mRR) requires catalytic (mR1) and free radical-containing (mR2) subunits and is regulated by nucleoside triphosphate allosteric effectors. Here we present a new, comprehensive, and quantitative model for allosteric control of mRR enzymatic activity based on molecular mass, ligand binding, and enzyme activity studies. In this model, nucleotide binding to the specificity site (s-site) drives formation of an active R1(2)R2(2) dimer, ATP or dATP binding to the adenine-specific site (a-site) results in formation of an inactive tetramer, and ATP binding to the newly described hexamerization site (h-site) drives formation of active R1(6)R2(6) hexamer. In contrast, an earlier phenomenological model [Thelander, L., and Reichard, P. (1979) Annu. Rev. Biochem. 67, 71-98] (the "RT" model) ignores aggregation state changes and mistakenly rationalizes ATP activation versus dATP inhibition as reflecting different functional consequences of ATP versus dATP binding to the a-site. Our results suggest that the R1(6)R2(6) heterohexamer is the major active form of the enzyme in mammalian cells, and that the ATP concentration is the primary modulator of enzyme activity, coupling the rate of DNA biosynthesis with the energetic state of the cell. Using the crystal structure of the Escherichia coliR1 hexamer as a model for the mR1 hexamer, a scheme is presented that rationalizes the slow isomerization of the tetramer form and suggests an explanation for the low enzymatic activity of tetramers complexed with R2. The similar specific activities of R1(2)R2(2) and R1(6)R2(6) are inconsistent with a proposed model for R2(2) docking with R1(2) [Uhlin, U., and Eklund, H. (1994) Nature 370, 533-539], and an alternative is suggested.