ß2ARs: double edge sword in heart function.

Deng and colleagues highlight the importance of understanding the divergent roles of ß2-adrenoceptor (ß2AR) in high-fat diet-induced heart failure. ß2AR signaling has beneficial and detrimental effects depending on the context and level of activation. We discuss the importance of these findings and their implications in developing effective and safe therapies.

ß2-Adrenergic Receptor Enhances the Alternatively Activated Macrophages and Promotes Biliary Injuries Caused by Helminth Infection.

The autonomic nervous system has been studied for its involvement in the control of macrophages; however, the mechanisms underlying the interaction between the adrenergic receptors and alternatively activated macrophages (M2) remain obscure. Using FVB wild-type and beta 2 adrenergic receptors knockout, we found that ß2-AR deficiency alleviates hepatobiliary damage in mice infected with C. sinensis. Moreover, ß2-AR-deficient mice decrease the activation and infiltration of M2 macrophages and decrease the production of type 2 cytokines, which are associated with a significant decrease in liver fibrosis in infected mice. Our in vitro results on bone marrow-derived macrophages revealed that macrophages from Adrb2-/- mice significantly decrease M2 markers and the phosphorylation of ERK/mTORC1 induced by IL-4 compared to that observed in M2 macrophages from Adrb2+/+ . This study provides a better understanding of the mechanisms by which the ß2-AR enhances type 2 immune response through the ERK/mTORC1 signaling pathway in macrophages and their role in liver fibrosis.

Physiological Temperature Changes Fine-Tune ß 2- Adrenergic Receptor-Induced Cytosolic cAMP Accumulation.

Norepinephrine (NE) controls many vital body functions by activating adrenergic receptors (ARs). Average core body temperature (CBT) in mice is 37°C. Of note, CBT fluctuates between 36 and 38°C within 24 hours, but little is known about the effects of CBT changes on the pharmacodynamics of NE. Here, we used Peltier element-controlled incubators and challenged murine hypothalamic mHypoA -2/10 cells with temperature changes of ±1°C. We observed enhanced NE-induced activation of a cAMP-dependent luciferase reporter at 36 compared with 38°C. mRNA analysis and subtype specific antagonists revealed that NE activates ß 2- and ß 3-AR in mHypoA-2/10 cells. Agonist binding to the ß 2-AR was temperature insensitive, but measurements of cytosolic cAMP accumulation revealed an increase in efficacy of 45% ± 27% for NE and of 62% ± 33% for the ß 2-AR-selective agonist salmeterol at 36°C. When monitoring NE-promoted cAMP efflux, we observed an increase in the absolute efflux at 36°C. However, the ratio of exported to cytosolic accumulated cAMP is higher at 38°C. We also stimulated cells with NE at 37°C and measured cAMP degradation at 36 and 38°C afterward. We observed increased cAMP degradation at 38°C, indicating enhanced phosphodiesterase activity at higher temperatures. In line with these data, NE-induced activation of the thyreoliberin promoter was found to be enhanced at 36°C. Overall, we show that physiologic temperature changes fine-tune NE-induced cAMP signaling in hypothalamic cells via ß 2-AR by modulating cAMP degradation and the ratio of intra- and extracellular cAMP. SIGNIFICANCE STATEMENT: Increasing cytosolic cAMP levels by activation of G protein-coupled receptors (GPCR) such as the ß 2-adrenergic receptor (AR) is essential for many body functions. Changes in core body temperature are fundamental and universal factors of mammalian life. This study provides the first data linking physiologically relevant temperature fluctuations to ß 2-AR-induced cAMP signaling, highlighting a so far unappreciated role of body temperature as a modulator of the prototypic class A GPCR.

ß2-Adrenergic receptor agonist induced hepatic steatosis in mice: modeling nonalcoholic fatty liver disease in hyperadrenergic states.

Nonalcoholic fatty liver disease (NAFLD) is a spectrum of disorders ranging from hepatic steatosis [excessive accumulation of triglycerides (TG)] to nonalcoholic steatohepatitis, which can progress to cirrhosis and hepatocellular carcinoma. The molecular pathogenesis of steatosis and progression to more severe NAFLD remains unclear. Obesity and aging, two principal risk factors for NAFLD, are associated with a hyperadrenergic state. ß-Adrenergic responsiveness in liver increases in animal models of obesity and aging, and in both is linked to increased hepatic expression of ß2-adrenergic receptors (ß2-ARs). We previously showed that in aging rodents intracellular signaling from elevated hepatic levels of ß2-ARs may contribute to liver steatosis. In this study we demonstrate that injection of formoterol, a highly selective ß2-AR agonist, to mice acutely results in hepatic TG accumulation. Further, we have sought to define the intrahepatic mechanisms underlying ß2-AR mediated steatosis by investigating changes in hepatic expression and cellular localization of enzymes, transcription factors, and coactivators involved in processes of lipid accrual and disposition-and also functional aspects thereof-in livers of formoterol-treated animals. Our results suggest that ß2-AR activation by formoterol leads to increased hepatic TG synthesis and de novo lipogenesis, increased but incomplete ß-oxidation of fatty acids with accumulation of potentially toxic long-chain acylcarnitine intermediates, and reduced TG secretion-all previously invoked as contributors to fatty liver disease. Experiments are ongoing to determine whether sustained activation of hepatic ß2-AR signaling by formoterol might be utilized to model fatty liver changes occurring in hyperadrenergic states of obesity and aging, and thereby identify novel molecular targets for the prevention or treatment of NAFLD.NEW & NOTEWORTHY Results of our study suggest that ß2-adrenergic receptor (ß2-AR) activation by agonist formoterol leads to increased hepatic TG synthesis and de novo lipogenesis, incomplete ß-oxidation of fatty acids with accumulation of long-chain acylcarnitine intermediates, and reduced TG secretion. These findings may, for the first time, implicate a role for ß2-AR responsive dysregulation of hepatic lipid metabolism in the pathogenetic processes underlying NAFLD in hyperadrenergic states such as obesity and aging.

Thermogenic recruitment of brown and brite/beige adipose tissues is not obligatorily associated with macrophage accretion or attrition.

Cold- and diet-induced recruitment of brown adipose tissue (BAT) and the browning of white adipose tissue (WAT) are dynamic processes, and the recruited state attained is a state of dynamic equilibrium, demanding continuous stimulation to be maintained. An involvement of macrophages, classical proinflammatory (M1) or alternatively activated anti-inflammatory (M2), is presently discussed as being an integral part of these processes. If these macrophages play a mediatory role in the recruitment process, such an involvement would have to be maintained in the recruited state. We have, therefore, investigated whether the recruited state of these tissues is associated with macrophage accretion or attrition. We found no correlation (positive or negative) between total UCP1 mRNA levels (as a measure of recruitment) and proinflammatory macrophages in any adipose depot. We found that in young chow-fed mice, cold-induced recruitment correlated with accretion of anti-inflammatory macrophages; however, such a correlation was not seen when cold-induced recruitment was studied in diet-induced obese mice. Furthermore, the anti-inflammatory macrophage accretion was mediated via ß1/ß2-adrenergic receptors; yet, in their absence, and thus in the absence of macrophage accretion, recruitment proceeded normally. We thus conclude that the classical recruited state in BAT and inguinal (brite/beige) WAT is not paralleled by macrophage accretion or attrition. Our results make mediatory roles for macrophages in the recruitment process less likely.NEW & NOTEWORTHY A regulatory or mediatory role-positive or negative-for macrophages in the recruitment of brown adipose tissue is presently discussed. As the recruited state in the tissue is a dynamic process, maintenance of the recruited state would need persistent alterations in macrophage complement. Contrary to this expectation, we demonstrate here an absence of alterations in macrophage complement in thermogenically recruited brown-or brite/beige-adipose tissues. Macrophage regulation of thermogenic capacity is thus less likely.

Effects of ß-adrenoceptor activation on haemodynamics during hypoxic stress in rats.

NEW FINDINGS: What is the central question of this study? The acute hypoxic compensatory reaction is based on haemodynamic changes, and ß-adrenoceptors are involved in haemodynamic regulation. What is the role of ß-adrenoceptors in haemodynamics during hypoxic exposure? What is the main finding and its importance? Activation of ß2 -adrenoceptors attenuates the increase in pulmonary artery pressure during hypoxic exposure. This compensatory reaction activated by ß2 -adrenoceptors during hypoxic stress is very important to maintain the activities of normal life. ABSTRACT: The acute hypoxic compensatory reaction is accompanied by haemodynamic changes. We monitored the haemodynamic changes in rats undergoing acute hypoxic stress and applied antagonists of ß-adrenoceptor (ß-ARs) subtypes to reveal the regulatory role of ß-ARs on haemodynamics. Sprague-Dawley rats were randomly divided into control, atenolol (ß1 -AR antagonist), ICI 118,551 (ß2 -AR antagonist) and propranolol (non-selective ß-AR antagonist) groups. Rats were continuously recorded for changes in haemodynamic indexes for 10 min after administration. Then, a hypoxic ventilation experiment [15% O2 , 2200 m a.sl., 582 mmHg (0.765 Pa), PO2 87.3 mmHg; Xining, China] was conducted, and the indexes were monitored for 5 min after induction of hypoxia. Plasma catecholamine concentrations were also measured. We found that, during normoxia, the mean arterial pressure, heart rate, ascending aortic blood flow and pulmonary artery pressure were reduced in the propranolol and atenolol groups. Catecholamine concentrations were increased significantly in the atenolol group compared with the control group. During hypoxia, mean arterial pressure and total peripheral resistance were decreased in the control, propranolol and ICI 118,551 groups. Pulmonary arterial pressure and pulmonary vascular resistance were increased in the propranolol and ICI 118,551 groups. During hypoxia, catecholamine concentrations were increased significantly in the control group, but decreased in ß-AR antagonist groups. In conclusion, the ß2 -AR is involved in regulation of pulmonary haemodynamics in the acute hypoxic compensatory reaction, and the activation of ß2 -ARs attenuates the increase in pulmonary arterial pressure during hypoxic stress. This compensatory reaction activated by ß2 -ARs during hypoxic stress is very important to maintain activities of normal life.

ß2 Adrenergic Regulation of the Phagocytic and Microbicide Capacity of Circulating Monocytes: Influence of Obesity and Exercise.

Obese individuals present anomalous immune/inflammatory responses with dysregulations in neuroendocrine responses and immune/stress feedback mechanisms. In this context, exercise and ß2 adrenergic activation present monocyte-mediated anti-inflammatory effects that are modulated by obesity. However, these anti-inflammatory effects could immunocompromise the monocyte-mediated innate response against a pathogen challenge. Thus, the objective of this work was to evaluate the effect of obesity, and exercise in this condition, on the ß2 adrenergic regulation of the phagocytic and microbicide capacity of circulating monocytes. C57BL/6J mice were allocated to different sedentary or exercised, lean or obese groups. Obese mice showed a lower monocyte-mediated innate response than that of lean mice. Globally, selective ß2 adrenergic receptor agonist terbutaline decreased the innate response of monocytes from lean and obese sedentary animals, whereas exercise stimulated it. Exercise modulates ß2 adrenergic regulation of the innate response in lean and obese animals, with a global stimulatory or neutral effect, thus abolishing the inhibitory effect of terbutaline occurring in sedentary animals. These effects cannot be explained only by changes in the surface expression of toll-like receptors. Therefore, in general, terbutaline does not hinder the effects of regular exercise, but regular exercise does abolish the effects of terbutaline in sedentary individuals.

Underlying mechanism of vasorelaxant effect exerted by 3,5,7,2',4'-pentahydroxyflavone in rats aortic ring.

Morin (3,5,7,2',4'-pentahydroxyflavone) is a yellow coloured natural flavonoid found in plants of the Moraceae family. This favonoid is easily sources from readily available fruits, vegetables and eve certain beverages. Among the sources that was identified, it is clear that morin is most abundantly found in almond, old fustic, Indian guava, and Osage orange. Multiple studies have suggested that morin has multiple therapeutic actions and possess potential to be a functional potent drug. Previous studies demonstrated that morin is capable of resolving deoxycorticosterone acetate-salt-induced hypertension and possess strong vasorelaxant properties. However, the exact mechanisms remains unknown. Therefore, this study is designed to investigate the in vitro mechanism of morin-induced vasorelaxant effects. The underlying mechanisms of morin's vasorelaxant activities were evaluated on thoracic aortic rings isolated from Sprague-Dawley rats. Results from the study demonstrated morin causing vasodilatory reaction in phenylephrine and potassium chloride pre-contracted endothelium-intact aortic rings with the effect being significantly affected in endothelium-denuded aortic rings. Pre-incubation of the aortic rings with ODQ (selective cGMP-independent sGC inhibitor), indomethacin (nonselective COX inhibitor), L-NAME (endothelial nitric oxide inhibitor), propranolol (ß2-adrenegic receptors blocker), and atropine (muscarinic receptors blocker) significantly reduced the vasorelaxant effect of morin. It was also found to be able to reduce the intracellular calcium level by blocking VOCC and calcium intake from the extracellular environment and the intracellular release of calcium from the sarcoplasmic reticulum. The present study showed that the vasorelaxant effect of morin potentially involves the NO/sGC, muscarinic receptors, ß2-adrenegic receptors, and calcium channels.

Lippia alnifolia essential oil induces relaxation on Guinea-pig trachea by multiple pathways.

ETHNOPHARMACOLOGICAL RELEVANCE: Lippia alnifolia Mart. & Schauer, known as "alecrim-do-mato", "alecrim-de-vaqueiro" and "pedrécio", is used in folk medicine as antiseptic and to treat diseases that affect respiratory system, like bronchitis and asthma. AIM OF THE STUDY: The aim of this work was to investigate the spasmolytic activity and relaxant mechanism of the Lippia alnifolia essential oil (EOLA) on isolated guinea-pig trachea and to correlate with its use in folk medicine. MATERIALS AND METHODS: Leaves from L. alnifolia were collected in Pico das Almas, Chapada Diamantina, situated in the city of Rio de Contas, Bahia, Brazil. EOLA was extracted by hydrodistillation, analyzed by GC/FID and GC/MS and the volatile constituents were identified. Spasmolytic activity was assayed in isolated guinea-pig trachea pre-contracted with carbachol 1 µM or histamine 10 µM. Relaxant mechanism of EOLA was determined comparing concentration-response curves in the presence or absence of different blockers. RESULTS: Chemical analysis revealed the presence of carvone (60 ±â€¯0.8%) as major constituent. EOLA (1-243 µg/mL) relaxed isolated guinea-pig trachea pre-contracted with carbachol 1 µM [EC50 = 53.36 (44.75-63.51) µg/mL] or histamine 10 µM [EC50 = 5.42 (4.42-6.65) µg/mL]. The pre-incubation of 4-aminopyridine in histamine-induced contractions did not alter significantly the relaxant effect of EOLA. However, the presence of cesium chloride, glibenclamide, tetraethylammonium, propranolol, indomethacin, dexamethasone, hexamethonium, atropine, L-NAME, methylene blue or ODQ reduced EOLA relaxant effect. EOLA 18 µg/mL pre-incubation in calcium-free medium reduced histamine-evoked contractions, but did not alter histamine contractions in the presence of nifedipine. CONCLUSIONS: Lippia alnifolia essential oil has spasmolytic activity on isolated guinea-pig trachea and its mechanism of action possibly involves the activation of multiple signal transduction pathways, which culminate in potassium channels activation and cytosolic calcium reduction.

Dexamethasone attenuates inflammatory-mediated suppression of ß2-adrenoceptor expression in rat primary mixed glia.

ß2-adrenoceptors are G-protein coupled receptors expressed on both astrocytes and microglia that play a key role in mediating the anti-inflammatory actions of noradrenaline in the CNS. Here the effect of an inflammatory stimulus (LPS + IFN-γ) was examined on glial ß2-adrenoceptor expression and function. Exposure of glia to LPS + IFN-γ decreased ß2-adrenoceptor mRNA and agonist-stimulated production of the intracellular second messenger cAMP. Pre-treatment with the synthetic glucocorticoid and potent anti-inflammatory agent dexamethasone prevented the LPS + IFN-γ-induced suppression of ß2-adrenoceptor mRNA expression. These results raise the possibility that inflammation-mediated ß2-adrenoceptor downregulation in glia may dampen the innate anti-inflammatory properties of noradrenaline in the CNS.

Watching helical membrane proteins fold reveals a common N-to-C-terminal folding pathway.

To understand membrane protein biogenesis, we need to explore folding within a bilayer context. Here, we describe a single-molecule force microscopy technique that monitors the folding of helical membrane proteins in vesicle and bicelle environments. After completely unfolding the protein at high force, we lower the force to initiate folding while transmembrane helices are aligned in a zigzag manner within the bilayer, thereby imposing minimal constraints on folding. We used the approach to characterize the folding pathways of the Escherichia coli rhomboid protease GlpG and the human ß2-adrenergic receptor. Despite their evolutionary distance, both proteins fold in a strict N-to-C-terminal fashion, accruing structures in units of helical hairpins. These common features suggest that integral helical membrane proteins have evolved to maximize their fitness with cotranslational folding.

Optogenetic activation of intracellular antibodies for direct modulation of endogenous proteins.

Intracellular antibodies have become powerful tools for imaging, modulating and neutralizing endogenous target proteins. Here, we describe an optogenetically activated intracellular antibody (optobody) consisting of split antibody fragments and blue-light inducible heterodimerization domains. We expanded this optobody platform by generating several optobodies from previously developed intracellular antibodies, and demonstrated that photoactivation of gelsolin and ß2-adrenergic receptor (ß2AR) optobodies suppressed endogenous gelsolin activity and ß2AR signaling, respectively.

Phosphodiesterase 5 Associates With ß2 Adrenergic Receptor to Modulate Cardiac Function in Type 2 Diabetic Hearts.

Background In murine heart failure models and in humans with diabetic-related heart hypertrophy, inhibition of phosphodiesterase 5 (PDE5) by sildenafil improves cardiac outcomes. However, the mechanism by which sildenafil improves cardiac function is unclear. We have observed a relationship between PDE5 and ß2 adrenergic receptor (ß2AR), which is characterized here as a novel mechanistic axis by which sildenafil improves symptoms of diabetic cardiomyopathy. Methods and Results Wild-type and ß2AR knockout mice fed a high fat diet (HFD) were treated with sildenafil, and echocardiogram analysis was performed. Cardiomyocytes were isolated for excitation-contraction (E-C) coupling, fluorescence resonant energy transfer, and proximity ligation assays; while heart tissues were implemented for biochemical and histological analyses. PDE5 selectively associates with ß2AR, but not ß1 adrenergic receptor, and inhibition of PDE5 with sildenafil restores the impaired response to adrenergic stimulation in HFD mice and isolated ventriculomyocytes. Sildenafil enhances ß adrenergic receptor (ßAR)-stimulated cGMP and cAMP signals in HFD myocytes. Consequently, inhibition of PDE5 leads to protein kinase G-, and to a lesser extent, calcium/calmodulin-dependent kinase II-dependent improvements in adrenergically stimulated E-C coupling. Deletion of ß2AR abolishes sildenafil's effect. Although the PDE5-ß2AR association is not altered in HFD, phosphodiesterase 3 displays an increased association with the ß2AR-PDE5 complex in HFD myocytes. Conclusions This study elucidates mechanisms by which the ß2AR-PDE5 axis can be targeted for treating diabetic cardiomyopathy. Inhibition of PDE5 enhances ß2AR stimulation of cGMP and cAMP signals, as well as protein kinase G-dependent E-C coupling in HFD myocytes.

Can physical activity ameliorate immunosenescence and thereby reduce age-related multi-morbidity?

Remodelling of the immune system with age - immunosenescence - is a substantial contributor to poor health in older adults, with increasing risk of infections, cancer and chronic inflammatory disease contributing to age-related multi-morbidity. What is seldom considered when examining the immune response of an aged individual is that the immune system is profoundly influenced by physical activity. Habitual physical activity levels decline with age, with significant consequences for muscle mass and function. Skeletal muscle is a major immune regulatory organ and generates a range of proteins, termed myokines, which have anti-inflammatory and immunoprotective effects. Several studies indicate that maintaining physical activity has immune benefits in older adults, for example, it reduces the systemic inflammation associated with chronic age-related diseases. Here, we discuss how physical activity can prevent or ameliorate age-related multi-morbidity by boosting immune function, and we consider whether physical activity could improve immunotherapy outcomes in age-related conditions such as cancer.

ß-adrenergic modulation of discrimination learning and memory in the auditory cortex.

Despite vast literature on catecholaminergic neuromodulation of auditory cortex functioning in general, knowledge about its role for long-term memory formation is scarce. Our previous pharmacological studies on cortex-dependent frequency-modulated tone-sweep discrimination learning of Mongolian gerbils showed that auditory-cortical D1/5 -dopamine receptor activity facilitates memory consolidation and anterograde memory formation. Considering overlapping functions of D1/5 -dopamine receptors and ß-adrenoceptors, we hypothesised a role of ß-adrenergic signalling in the auditory cortex for sweep discrimination learning and memory. Supporting this hypothesis, the ß1/2 -adrenoceptor antagonist propranolol bilaterally applied to the gerbil auditory cortex after task acquisition prevented the discrimination increment that was normally monitored 1 day later. The increment in the total number of hurdle crossings performed in response to the sweeps per se was normal. Propranolol infusion after the seventh training session suppressed the previously established sweep discrimination. The suppressive effect required antagonist injection in a narrow post-session time window. When applied to the auditory cortex 1 day before initial conditioning, ß1 -adrenoceptor-antagonising and ß1 -adrenoceptor-stimulating agents retarded and facilitated, respectively, sweep discrimination learning, whereas ß2 -selective drugs were ineffective. In contrast, single-sweep detection learning was normal after propranolol infusion. By immunohistochemistry, ß1 - and ß2 -adrenoceptors were identified on the neuropil and somata of pyramidal and non-pyramidal neurons of the gerbil auditory cortex. The present findings suggest that ß-adrenergic signalling in the auditory cortex has task-related importance for discrimination learning of complex sounds: as previously shown for D1/5 -dopamine receptor signalling, ß-adrenoceptor activity supports long-term memory consolidation and reconsolidation; additionally, tonic input through ß1 -adrenoceptors may control mechanisms permissive for memory acquisition.

ADRB2 suppresses IL-13-induced allergic rhinitis inflammatory cytokine regulated by miR-15a-5p.

Allergic rhinitis (AR) is a common hypersensitive disease that troubles patients a lot. Nasal epithelial cells (NECs), as the outmost protection of inhalation, play an important role in AR allergic response. Adrenoceptor beta 2 (ADRB2) is an important gene in inflammatory response, which has become the hot spot for AR development and treatment in recent years. MiR-15a-5p has been proved to be involved in AR immune response as the upstream regulator of ADRB2. Human primary NECs were isolated and stimulated by IL-13. qRT-PCR assay was used to detect the RNA level of target genes. ELISA and Western blotting were applied to detect target protein levels. Luciferase reporter assay and biotin pull-down assay were performed to test molecules interaction. ADRB2 was highly expressed in nasal mucosa of AR patients and was positively correlated with IL-13 stimulation, and knockdown of ADRB2 inhibited IL-13-induced expression of GM-CSF, eotaxin, and MUC5AC in NECs. ADRB2 was directly targeted by miR-15a-5p, and miR-15a-5p inhibited IL-13-induced expression of GM-CSF, eotaxin, and MUC5AC in NECs. ADRB2 mediated the effect of miR-15a-5p on the regulation of nasal epithelial immune responses. ADRB2 is negatively regulated by miR-15a-5p, which inhibits IL-13-induced nasal epithelial inflammatory responses.

The Stimulatory Effects of Medicinal Plants on ß2-adrenoceptors of Tracheal Smooth Muscle.

Medicinal plants have been identified and used as primary sources in prevention and treatment of pulmonary diseases (mainly obstructive pulmonary diseases) from ancient times due to various pharmacological activities. In this review, the stimulatory effects of extracts, some fractions and constituents of medicinal plants on ß2-adrenoceptors which could be used as possible therapeutic agents in the future were reviewed. Various databases including; Medline, PubMed, ScienceDirect, Scopus, and Google Scholar were searched using stimulatory effect, ß2-adrenoceptors, possible mechanism, tracheal smooth muscle (TSM), medicinal plants and their constituents as keywords from 1985 to 2017. All studied plants including; Nigella sativa, Rosa damascena, Thymus vulgaris, Carum copticom, Carum carvi, Zataria multiflora, Crocus sativus, Cuminum cyminum, Liomnia acidissima, Portulaca oleraceae, Satureja hortensis, Ephedra sinica and Achillea millefolium showed relaxant effect on tracheal smooth muscle with a stimulatory effect on ß2-adrenoceptors mechanism. The studied plants and their constituents could be of therapeutic value in clinical practice as a bronchodilatory drug by ß2-adrenoceptors stimulatory mechanism for treatment of obstructive pulmonary diseases.

Direct visualization of single-molecule membrane protein interactions in living cells.

Interactions between membrane proteins are poorly understood despite their importance in cell signaling and drug development. Here, we present a co-immunoimmobilization assay (Co-II) enabling the direct observation of membrane protein interactions in single living cells that overcomes the limitations of currently prevalent proximity-based indirect methods. Using Co-II, we investigated the transient homodimerizations of epidermal growth factor receptor (EGFR) and beta-2 adrenergic receptor (ß2-AR) in living cells, revealing the differential regulation of these receptors' dimerizations by molecular conformations and microenvironment in a plasma membrane. Co-II should provide a simple, rapid, and robust platform for visualizing both weak and strong protein interactions in the plasma membrane of living cells.

ADRB2 gene polymorphism modulates the retention of fear extinction memory.

Individual differences in regulation of fear and extinction memory play significant roles in the aetiology development of post-traumatic stress disorder (PTSD). Previous animal based studies showed that the activity of ß-adrenergic receptors (ß-ARs) are involved in memory modulation. However in humans it is not clear that whether genetic variability in ß-ARs contributes to individual differences of fear and extinction memory. In the current study, we investigated the role of a common single-nucleotide polymorphism of ß2-adrenergic receptor (ADRB2) gene in fear memory acquisition, fear memory extinction, extinction recall and fear generalization in human participants. Ninety-one male participants were exposed to a Pavlovian fear conditioning and their fear responses were assessed by the skin conductance response. Participants were genotyped for a polymorphism (rs2400207) located within the promoter region of the human ADRB2. Differences between genotypes were observed in the extinction memory recall test but not in fear acquisition, extinction learning and fear generalization. Particularly, A-allele carriers of rs2400707 displayed successful retention of extinction memory and prevented the return of fear during recall test. The results revealed the involvement of human noradrenergic system in the retention of extinction memory and genetic variability in this system may underlie individual differences in PTSD. Furthermore, rs2400207 polymorphism of ADRB2 gene may play a key role in the treatment efficacy of PTSD and can be a basis for future studies investigating a personalized medicine for fear memory related disorders.