Different Modes Of Activation Research Articles

G protein selectivity profile of GPR56/ADGRG1 and its effect on downstream effectors.

GPR56, an adhesion G-protein coupled receptor (aGPCRs) with constitutive and ligand-promoted activity, is involved in many physiological and pathological processes. Whether the receptor's constitutive or ligand-promoted activation occur through the same molecular mechanism, and whether different activation modes lead to functional selectivity between G proteins is unknown. Here we show that GPR56 constitutively activates both G12 and G13. Unlike constitutive activation and activation with 3-a-acetoxydihydrodeoxygedunin (3αDOG), stimulation with an antibody, 10C7, directed against GPR56's extracellular domain (ECD) led to an activation that favors G13 over G12. An autoproteolytically deficient mutant, GPR56-T383A, was also activated by 10C7 indicating that the tethered agonist (TA) exposed through autocatalytic cleavage, is not required for this activation modality. In contrast, this proteolysis-resistant mutant could not be activated by 3aDOG indicating different modes of activation by the two ligands. We show that an N-terminal truncated GPR56 construct (GPR56-Δ1-385) is devoid of constitutive activity but was activated by 3aDOG. Similarly to 3aDOG, 10C7 promoted the recruitment of b-arrestin-2 but GPR56 internalization was β-arrestin independent. Despite the slow activation mode of 10C7 that favors G13 over G12, it efficiently activated the downstream Rho pathway in BT-20 breast cancer cells. These data show that different GPR56 ligands have different modes of activation yielding differential G protein selectivity but converging on the activation of the Rho pathway both in heterologous expressions system and in cancer cells endogenously expressing the receptor. 10C7 is therefore an interesting tool to study both the processes underlying GPR56 activity and its role in cancer cells.

G protein selectivity profile of GPR56/ADGRG1 and its effect on downstream effectors

GPR56, an adhesion G-protein coupled receptor (aGPCRs) with constitutive and ligand-promoted activity, is involved in many physiological and pathological processes. Whether the receptor’s constitutive or ligand-promoted activation occur through the same molecular mechanism, and whether different activation modes lead to functional selectivity between G proteins is unknown. Here we show that GPR56 constitutively activates both G12 and G13. Unlike constitutive activation and activation with 3-α-acetoxydihydrodeoxygedunin (3αDOG), stimulation with an antibody, 10C7, directed against GPR56’s extracellular domain (ECD) led to an activation that favors G13 over G12. An autoproteolytically deficient mutant, GPR56-T383A, was also activated by 10C7 indicating that the tethered agonist (TA) exposed through autocatalytic cleavage, is not required for this activation modality. In contrast, this proteolysis-resistant mutant could not be activated by 3αDOG indicating different modes of activation by the two ligands. We show that an N-terminal truncated GPR56 construct (GPR56-Δ1-385) is devoid of constitutive activity but was activated by 3αDOG. Similarly to 3αDOG, 10C7 promoted the recruitment of β-arrestin-2 but GPR56 internalization was β-arrestin independent. Despite the slow activation mode of 10C7 that favors G13 over G12, it efficiently activated the downstream Rho pathway in BT-20 breast cancer cells. These data show that different GPR56 ligands have different modes of activation yielding differential G protein selectivity but converging on the activation of the Rho pathway both in heterologous expressions system and in cancer cells endogenously expressing the receptor. 10C7 is therefore an interesting tool to study both the processes underlying GPR56 activity and its role in cancer cells.

Base Metal-Controlled Chemodivergent Cyclization of Propargylamines for the Atom-Economic Synthesis of Nitrogen Heterocycles.

Herein, a base metal-enabled chemodivergent cyclization of propargylamines for the atom-economic construction of nitrogen heterocycles has been developed. Due to the different modes of activation of metal to propargylamine, copper-catalyzed 6-endo-dig cyclization generates functionalized 2-substitued quinoline-4-carboxylates, while iron-promoted cascade amino Claisen rearrangement, aromatization, and aza-Michael addition afford diverse 2-substituted indole-3-carboxylate derivatives. Excellent selectivity, broad functional group tolerance, mild conditions, and flexible late-stage functionalization illustrate the high efficiency and synthetic utility of this chemodivergent reaction.

Activation of N−O σ Bonds with Transition Metals: A Versatile Platform for Organic Synthesis and C−N Bonds Formation**

AbstractN−O σ bonds containing compounds are versatile substrates for organic synthesis under transition metal catalysis. Their ability to react through both polar (oxidative addition, formation of metallanitrene, nucleophilic substitution) and radical pathways (single electron transfer, homolytic bond scission) have triggered the development of various synthetic methodologies, particularly toward synthesizing nitrogen‐containing compounds. In this review, we discuss the different modes of activation of N−O bonds in the presence of transition metal catalysts, emphasizing the experimental and computational mechanistic proofs in the literature to help to design new synthetic pathways toward the synthesis of C−N bonds.

Global dynamics of neural mass models

Neural mass models are used to simulate cortical dynamics and to explain the electrical and magnetic fields measured using electro- and magnetoencephalography. Simulations evince a complex phase-space structure for these kinds of models; including stationary points and limit cycles and the possibility for bifurcations and transitions among different modes of activity. This complexity allows neural mass models to describe the itinerant features of brain dynamics. However, expressive, nonlinear neural mass models are often difficult to fit to empirical data without additional simplifying assumptions: e.g., that the system can be modelled as linear perturbations around a fixed point. In this study we offer a mathematical analysis of neural mass models, specifically the canonical microcircuit model, providing analytical solutions describing slow changes in the type of cortical activity, i.e. dynamical itinerancy. We derive a perturbation analysis up to second order of the phase flow, together with adiabatic approximations. This allows us to describe amplitude modulations in a relatively simple mathematical format providing analytic proof-of-principle for the existence of semi-stable states of cortical dynamics at the scale of a cortical column. This work allows for model inversion of neural mass models, not only around fixed points, but over regions of phase space that encompass transitions among semi or multi-stable states of oscillatory activity. Crucially, these theoretical results speak to model inversion in the context of multiple semi-stable brain states, such as the transition between interictal, pre-ictal and ictal activity in epilepsy.

Polarity of c-di-GMP synthesis and degradation.

The bacterial cell pole has long been recognized as a defined compartment for enzymatic activities that are important or even vital for the cell. Polarity of diguanylate cyclases and phosphodiesterases, enzymes that synthesize and degrade the second messenger c-di-GMP, has now been demonstrated for several bacterial systems. Here we review these polar regulatory systems and show how the asymmetry of c-di-GMP production and turnover in concert with different modes of activation and deactivation creates heterogeneity in cellular c-di-GMP levels. We highlight how this heterogeneity generates a diverse set of phenotypic identities or states and how this may benefit the cell population, and we discuss reasons why the polarity of c-di-GMP signaling is probably widespread among bacteria.

The Direct Effects Of β-hydroxybutyrate On Skeletal Muscle Fatiguability And Recovery

PURPOSE: Ketone bodies compose a group of energy substrates that may improve skeletal muscle performance, possibly by sparing glycogen and improving metabolic efficiency. This study aims to determine the direct effects of the ketone body β-hydroxybutyrate (3-OHB) on skeletal muscle fatiguability and recovery. METHODS: Rat soleus muscles were isolated and placed at 30 °C in one of four modified Krebs-Ringer solutions: No energy substrate, glucose (5 mM), Na-3-OHB (10 mM), or glucose (5 mM) + Na-3-OHB (10 mM). Muscles were electrically stimulated to contract and thereby fatigued for 90 minutes by a dynamic contraction protocol designed to mimic rodent locomotion. Peak force was measured during isometric twitch, doublet, non-fused tetanus (15 Hz), and tetanic (60 Hz) muscle activation. Assessments were performed before and after fatigue and during 90 min of recovery. Muscle glycogen content was determined at the end of the recovery period. RESULTS: Peak force declined to ~50% following the fatigue protocol with no significant differences between groups. After 90 min of recovery, muscles with no energy substrates available had regained tetanic force to 54% of the pre-fatigue value. The other groups recovered significantly more force: 3-OHB 61% (p = 0,016), glucose 62% (p = 0.004), and glucose +3-OHB 66% (p < 0,001). There were no major differences between different modes of activation. Compared with no energy substrate, the availability of glucose in the buffers resulted in 21% (p = 0.042) and 20% (p = 0.049) higher muscle glycogen concentrations for glucose only and glucose +3-OHB, respectively. Glycogen concentrations in muscles only exposed to 3-OHB were not significantly different from the glucose groups nor the no energy substrate group. CONCLUSION: 3-OHB aids initial force recovery when no other energy substrates are available to the muscle. However, compared to glucose, 3-OHB does not delay fatigue or improve recovery.

Triclosan Influences on Reproductive Physiology of Climbing Perch in the Spawning Phase

Abstract The endocrine-disrupting effects of triclosan, an antimicrobial agent, and its involvement in reproductive responses mediated through different modes of activity in various fish species have been documented. The present study aims to explore whether triclosan at environmentally relevant and sublethal concentrations could influence the reproductive physiology of the fish Anabas testudineus in the spawning phase. Fish were exposed to triclosan at environmentally relevant (0.009 and 9 µg L−1) and sublethal (176.7 µg L−1) concentrations for 4, 7, 30 and 60 d during the spawning phase for evaluating the reproductive potential of the fish. Triclosan exposure caused a significant (P&lt;0.05) reduction in the level of total protein in gonads and liver tissues while increasing blood plasma to meet the energy demand and overcome metabolic stress. Impairment in gonadal steroidogenesis was evidenced by the reduction in the activities of 3β- and 17β-hydroxysteroid dehydrogenases associated with alteration in the levels of serum gonadotropins, sex steroid hormones and vitellogenin. Triclosan exposure caused a reduction in the rate of fecundity in females and declined sperm counts, motility and viability in males. Histological lesions in gonadal tissues further confirmed the reproductive toxicity of triclosan, which in turn could contribute to the reproductive failure of the fish.

Identification and characterization of two xyloglucan-specific endo-1,4-glucanases in Aspergillus oryzae

Aspergillus oryzae produces glycoside hydrolases to degrade xyloglucan. We identified and characterized two xyloglucan-specific endo-1,4-glucanases (xyloglucanases) named Xeg12A and Xeg5A. Based on their amino acid sequences, Xeg12A and Xeg5A were classified into glycoside hydrolase families GH12 and GH5, respectively. Xeg12A degrades tamarind seed xyloglucan polysaccharide into xyloglucan oligosaccharides containing four glucopyranosyl residues as main chains, including heptasaccharides (XXXG: Glc4Xyl3), octasaccharides (XXLG and XLXG: Glc4Xyl3Gal1), and nonasaccharides (XLLG: Glc4Xyl3Gal2). By contrast, Xeg5A produces various xyloglucan oligosaccharides from xyloglucan. Xeg5A hydrolyzes xyloglucan into not only XXXG, XXLG/XLXG, and XLLG but also disaccharides (isoprimeverose: Glc1Xyl1), tetrasaccharides (XX: Glc2Xyl2 and LG: Glc2Xyl1Gal1), and so on. Xeg12A is a typical endo-dissociative-type xyloglucanase that repeats hydrolysis and desorption from xyloglucan. Conversely, Xeg5A acts as an endo-processive-type xyloglucanase that hydrolyzes xyloglucan progressively without desorption. These results indicate that although both Xeg12A and Xeg5A contribute to the degradation of xyloglucan, they have different modes of activity toward xyloglucan, and the hydrolysis machinery of Xeg5A is unique compared with that of other known GH5 enzymes. KEY POINTS: • We identified two xyloglucanases, Xeg12A and Xeg5A, in A. oryzae. • Modes of activity and regiospecificities of Xeg12A and Xeg5A were clearly different. • Xeg5A is a unique xyloglucanase that produces low-molecular-weight oligosaccharides.

U.S. Food and Drug Administration-Certified Food Dyes as Organocatalysts in the Visible Light-Promoted Chlorination of Aromatics and Heteroaromatics.

Seven FDA-certified food dyes have been investigated as organocatalysts. As a result, Fast Green FCF and Brilliant Blue FCF have been discovered as catalysts for the chlorination of a wide range of arenes and heteroarenes in moderate to excellent yields and high regioselectivity. Mechanistic investigations of the separate systems indicate that different modes of activation are in operation, with Fast Green FCF being a light-promoted photoredox catalyst that is facilitating a one-electron oxidation of N-chlorosuccinimide (NCS) and Brilliant Blue FCF serving as a chlorine-transfer catalyst in its sulfonphthalein form with 1,3-dichloro-5,5-dimethylhydantoin (DCDMH) as stoichiometric chlorine source. Dearomatization of naphthol and indole substrates was observed in some examples using the Brilliant Blue/DCDMH system.

Learning from ancestors.

Predicting ancestral sequences of protein kinases reveals the molecular details that underlie different modes of activation.

Factors controlling frequency of turbidites in the Bengal fan during the last 248 kyr cal BP: Clues from a presently inactive channel

The seafloor of the Bay of Bengal is covered by thick sediment deposits that constitute the largest turbiditic system in the world. This system is fed primarily by the Ganges and Brahmaputra rivers, which drain the high Himalayan ranges. Sediment transfers from the delta to the deep-sea fan take place as turbidity currents in channel-levee systems. Previous studies have shown that, during high sea-level stand periods, the sediments were being mainly stored in the Ganges-Brahmaputra delta, and turbiditic transfer was occurring through active channels. Most of these channels are now inactive and sealed by hemipelagic deposits. However, the evolution of the inactive channels during the last sea-level variations has never been described in detail. Sedimentation in the currently active channel, the Active Valley, was particularly important during the last sea-level rise, which suggests a very good connection between the fluvial systems and the deep turbidite system at this time. During the MONOPOL cruise (2012), we retrieved a giant piston core (MD12-3412) near the currently inactive E4 channel. Previous studies have hypothesized that this channel is connected to the Swatch of No Ground canyon on the upper fan. The upper part of the core covers the last ~250 kyr. It reveals that, contrary to what is known about the Active Valley, the turbidite activity in E4 took place mainly during low sea-level phases (glacial stages), and stopped around 11.8 kyr cal BP. This different mode of activity suggests that (i) E4 was not abandoned but served as a secondary channel, and (ii) that the supply of turbidite material at the site of core MD12-3412 was not related to past changes in summer monsoon strength. Periods of activation of the E4 channel observed on core MD12-3412 were previously identified on the shelf area, by Hubscher and Spiess (2005), as thick Forced Regression System Tracts (FRST) after a displacement of deltaic edifices. High turbidites record on the deep basin are mainly synchronous with sea-level fall and rise conditions, but mostly during low sea-level periods. This could be explained by a residual connection between the coastal system and the E4 channel during sea level low stands.

Indiscriminate nature of lung resident CD8+ TRM cells reactivation and their varied reactivation profiles

Abstract CD8+ tissue resident memory (TRM) cells are poised at the portals of infection and confer immediate protection upon reinfection. Despite the critical role of CD8+ TRM cells in long-term protective immunity, the precise mechanics governing their reactivation in-situ are unclear. Seminal work by Leo Lefrançois' group showed that circulating (TCIRC) memory CD8+ T cell depends on CD11c+ antigen-presenting cells (APCs) for reactivation, however, TRM cells are reactivated within peripheral tissues, raising the question of whether the same principle is conserved. We examined this question, focusing on influenza infection, because APCs in the lung are well-defined and lung-resident TRM cells are critical for heterologous immunity to influenza. Using a TCR transgenic Nur77 reporter to delineate TCR-specific from bystander activation in CD8+ TRM cells, we characterized the superior reactivation kinetics in CD8+ TRM cell compared to CD8+ TCIRC. We also identified unique TCR-specific signatures and bystander-specific signatures in the kinetics of CD8+ TRM cells and TCIRC cells reactivation respectively. While we observed the strict requirement for CD11c+APCs in TCR-driven CD8+ TCIRC reactivation, CD8+ TRM cells exhibit promiscuity in their interactions with antigen-presenting partners in that they can be reactivated by both hematopoetic and non-hematopoetic cells. This study explains how the anatomical location of CD8+ TRM cells can confer unique advantage by demonstrating their superior reactivation kinetics and the indiscriminate nature of CD8+ TRM cell reactivation as well as showcasing the transcription profiles of TRM and TCIRC cells following different modes of activation.

The Molecular Regulation and Functional Roles of NOX5.

NOX (NADPH oxidases) are a family of NADPH-dependent transmembrane enzymes that synthesize superoxide and other reactive oxygen species. There are seven isoforms (NOX1-5 and DUOX1-2) which derive from a common ancestral NOX. NOX enzymes are distinguished by different modes of activation, the types of ROS that are produced, the cell types where they are expressed, and distinct functional roles. NOX5 was one of the earliest eukaryotic Nox enzymes to evolve and ironically the last isoform to be discovered in humans. In the time since its discovery, our knowledge of the regulation of NOX5 has expanded tremendously, and we now have a more comprehensive understanding of the molecular mechanisms underlying NOX5-dependent ROS production. In contrast, the cell types where NOX5 is robustly expressed and its functional significance in health and disease remain an underdeveloped area. The goal of this chapter is to provide an up-to-date overview of the mechanisms regulating NOX5 function and its importance in human physiology and pathophysiology.

To Bind or Not to Bind: Unravelling GPCR Polypharmacology

Interaction of a single drug with multiple targets through "polypharmacology" is increasingly recognized as necessary for treatment of complex diseases, such as schizophrenia. G protein-coupled receptors (GPCRs) are major medicinal targets, and understanding the structural basis of both GPCR drug selectivity and promiscuity could provide novel avenues for drug development.

Current and future use of nucleo(s)tide prodrugs in the treatment of hepatitis C virus infection

This review describes the current state of discovery of past most important nucleoside and nucleotide prodrugs in the treatment of hepatitis C virus infection as well as future potential drugs currently in discovery or clinical evaluation. I highlight first generation landmark prodrug compounds which have been the foundations of incremental improvements toward the discovery and approval milestone of Sofosbuvir. Sofosbuvir is the first nucleotide prodrug marketed for hepatitis C virus treatment and the backbone of current combination therapies. Since this approval, new nucleotide prodrugs using the same design of Sofosbuvir McGuigan prodrug have emerged, some of them progressing through advanced clinical trials and may become available as new incremental alternative hepatitis C virus treatments in the future. Although since Sofosbuvir success, only minimal design efforts have been invested in finding better liver targeted prodrugs, a few novel prodrugs are being studied and their different modes of activation may prove beneficial over the heart/liver targeting ratio to reduce potential drug–drug interaction in combination therapies and yield safer treatment to patients. Prodrugs have long been avoided as much as possible in the past by development teams due to their metabolism and kinetic characterization complexity, but with their current success in hepatitis C virus treatment, and the knowledge gained in this endeavor, should become a first choice in future tissue targeting drug discovery programs beyond the particular case of nucleos(t)ide analogs.

Helicobacter pylori controls NLRP3 expression by regulating hsa-miR-223-3p and IL-10 in cultured and primary human immune cells.

Inflammasome-mediated production of mature IL-1β and IL-18 cytokines represents an important innate immune response against infecting pathogens. Helicobacter pylori, one of the most successful and persistent human pathogens, induces severe inflammation leading to gastritis and more serious gastric diseases. H. pylori modulates different immune responses for its survival and inflammasome signaling is manipulated by the cag pathogenicity island ( cagPAI), urease and VacA cytotoxin. Here we report that H. pylori regulates NLRP3 expression, an inflammasome forming regulator, in infected THP-1 monocytes. This response was independent of the major H. pylori pathogenicity-associated factors CagA, VacA, Cgt, FlaA and cagPAI. Two NLRP3 expression controlling factors, the NLRP3 mRNA targeting microRNA hsa-miR-223-3p and cytokine IL-10, were found to work in tandem for its regulation. H. pylori infection also induced copious amount of pro-IL-1β in THP-1 monocytes/macrophages but secreted a very low amount of mature IL-1β. Moreover, secreted IL-10 correlated with the down-regulation of nigericin-induced NLRP3 inflammasome activation of LPS-primed THP-1 monocytes and human PBMCs from volunteers. However, H. pylori-treated PBMCs secreted significantly more mature IL-1β throughout the infection period, which suggests a different mode of activation. Taken together, this study demonstrates targeting of inflammasome-forming NLRP3, an important innate immunity component, and crucial manipulation of pro- and anti-inflammatory cytokines in H. pylori infection.

X-ray characterization of triphenylphosphine-gold(I) olefin π-complexes and the revision of their stability in solution

A large number of cationic Au(I) π-complexes have been reported in the literature. However, a single X-ray structure of genuine [Au(PPh3)(hydrocarbon)]+ π-complex without any additional stabilization has not been published so far. We present herein isolation and X-ray characterization of several complexes of this type. Also, we show that these π-complexes are more stable than previously reported and we investigate different modes of activation of the [Au(PPh3)]Cl precatalyst on their stability in solution.

О возможностях прогноза аварийности водителей

The paper describes the approach to solving the problem of the high accident rate on the roads in Russia. The paper points the importance of driving analysis not as an activity but as a behavior, including a multicomponent combined activity of the driver and its interaction with other road users. It is proposed to solve the problem of accidents through conducting of preventive work, in particular, through forecasting the accident drivers. Forecast of accidents to be carried out on the basis of estimates of the ratio of driving style characteristics (determined by personal characteristics of the driver), and professional and important qualities of the driver. The paper sums the results up of the long-term empirical research, in the framework of which was created the questionnaire "Driving style". It was examined the relationship between the inclination of the driver to comply with traffic rules and accidents. It was investigated compensatory possibilities style of activity (such as the characteristics of the driving style) communication between personal (were analyzed accentuation of the driver's personality, lifestyle index, risk sentiment) and stylistic characteristics of the driver, determined by differences in the characteristics of the style of driving accidents and accident-free drivers. The paper gives an approach to the evaluation of driving style as a dangerous, unsafe and safe (to date in respect of the potential). Danger ─ non-hazardous driving style is associated with a propensityaverse of drivers to comply with traffic rules. Safety – insecurity determined by the nature of activity within the style of driving styles depending on whether it is compensation or compensatory nature. Relevance – potentiality of accident-fail-safety of driver is determined based of preserving the reliability of the driver in the different modes of activity.

How contexts promote and prevent relapse to drug seeking

The contexts where drugs are self-administered play an important role in regulating persistent drug taking and in relapse to such taking after periods of abstinence. Here, we review the behavioral and brain mechanisms enabling contexts to promote and prevent relapse to drug seeking. We review the key brain structures, their neuropharmacology and their connectivity. We discuss the similarities and differences between the mechanisms for context-induced reinstatement of drug seeking vs. other forms of relapse to drug seeking in animal models and we highlight the numerous deficits in our understanding. We emphasize that current understanding, although significant, defies explanations in terms of models at the level of brain structures and their connectivity. Rather, we show that there is significant functional compartmentalization and segregation within these structures during reinstatement and extinction of drug seeking that parallels their anatomical segregation into circuits and channels. A key challenge is to recognize this complexity, understand how these circuits and channels are organized, as well as understand how different modes of activity of ensembles of neurons within them promote abstinence or relapse to drug seeking.