Role of Helix 8 in Dopamine Receptor Signaling

G protein-coupled receptors (GPCRs) are membrane receptors whose agonist-induced dynamic conformational changes trigger heterotrimeric G protein activation, followed by GRK-mediated phosphorylation and arrestin-mediated desensitization. Cytosolic regions of GPCRs have been studied extensively because they are direct contact sites with G proteins, GRKs, and arrestins. Among various cytosolic regions, the role of helix 8 is least understood, although a few studies have suggested that it is involved in G protein activation, receptor localization, and/or internalization. In the present study, we investigated the role of helix 8 in dopamine receptor signaling focusing on dopamine D1 receptor (D1R) and dopamine D2 receptor (D2R). D1R couples exclusively to Gs, whereas D2R couples exclusively to Gi. Bioinformatic analysis implied that the sequences of helix 8 may affect GPCR-G protein coupling selectivity; therefore, we evaluated if swapping helix 8 between D1R and D2R changed G protein selectivity. Our results suggest that helix 8 is not involved in D1R-Gs or D2R-Gi coupling selectivity. Instead, we observed that D1R with D2R helix 8 or D1R with an increased number of hydrophobic residues in helix 8 relative to wild-type showed diminished β-arrestin-mediated desensitization, resulting in increased Gs signaling.

Arrestins: structural disorder creates rich functionality

Arrestins are soluble relatively small 44-46 kDa proteins that specifically bind hundreds of active phosphorylated GPCRs and dozens of non-receptor partners. There are binding partners that demonstrate preference for each of the known arrestin conformations: free, receptor-bound, and microtubule-bound. Recent evidence suggests that conformational flexibility in every functional state is the defining characteristic of arrestins. Flexibility, or plasticity, of proteins is often described as structural disorder, in contrast to the fixed conformational order observed in high-resolution crystal structures. However, protein-protein interactions often involve highly flexible elements that can assume many distinct conformations upon binding to different partners. Existing evidence suggests that arrestins are no exception to this rule: their flexibility is necessary for functional versatility. The data on arrestins and many other multi-functional proteins indicate that in many cases, "order" might be artificially imposed by highly non-physiological crystallization conditions and/or crystal packing forces. In contrast, conformational flexibility (and its extreme case, intrinsic disorder) is a more natural state of proteins, representing true biological order that underlies their physiologically relevant functions.

El significado del capital social "individual" en diabéticos receptores de cuidado en un contexto urbano colombiano / The meaning of "individual" social capital for diabetics receiving care in a Colombian city / O significado do capital social "individual" em diabéticos que precisam de cuidados dentro de um contexto urbano colombiano

Comprender el significado del capital social de la diabetes tipo 2 según género, dentro un contexto urbano colombiano. Investigación cualitativa del interaccionismo simbólico. 25 mujeres y 16 hombres, diabéticos, familiares, vecinos y personal asistencial participaron en seis grupos focales. Emergieron 850 códigos que se integraron en un set de 142 códigos de códigos para el ego, el alter y alter ego. Tres categorías y veinte subcategorías fueron identificadas para el diseño del "paradigma de la codificación". El significado no es igual para hombres y mujeres. Los vínculos sociales de las redes sociales, creados cotidianamente por la confianza y la solidaridad para el cuidado, son valorados de manera diferente, debido a experiencias y hechos sociales resultantes de la autoconfianza, la autoeficacia para el apoyo social principalmente y, la autoestima frente al manejo y control de la enfermedad. Los recursos sociales de un individuo son reificados para el manejo y cuidado de la enfermedad como estrategia para disminuir las inequidades en salud.

The aim of this study was to understand the meaning of social capital in relation to type 2 diabetes according to gender, within an urban setting in Colombia, based on a qualitative design for symbolic interactionism. Twenty-four women and 16 men with diabetes, family members, and healthcare personnel participated in six focus groups. A total of 850 codes emerged that comprised a set of 142 codes for ego, alter, and alter ego. Three categories and 20 subcategories were identified for the "coding paradigm design". The meaning differed between men and women. Social ties in social networks, created daily through trust and solidarity for care, were valued differently due to the social experiences and events resulting from self-confidence, self-efficacy for social support, and mainly self-esteem vis-à-vis management and control of the disease. An individual's social resources are reified for the management and care of the disease as a strategy to mitigate health inequalities. .

Compreender o significado do capital social, diabetes tipo 2 por sexo, um contexto urbano da Colômbia. pesquisa qualitativa do interacionismo simbólico. 25 mulheres e 16 homens, diabéticos, familiares, vizinhos e cuidadores participaram seis grupos focais. 850 códigos se que foram integrados em um conjunto de 142 codes para o ego, o alter e alter ego. Três categorias e vinte subcategorias foram identificados para o projeto de "codificação de paradigma". O significado não é o mesmo para homens e mulheres. Laços sociais das redes sociais criadas diariamente pela confiança e solidariedade são valorizados cuidado diferente, porque as experiências sociais e fatos resultantes da auto-confiança, auto-eficácia e de apoio social, principalmente, auto-gestão e controle em relação a doença. Os recursos sociais de um indivíduo são reificadas para a gestão o cuidado da doença como uma estratégia para reduzir as desigualdades na saúde.

β-arrestin1 promotes chronic myeloid leukemia cell proliferation by activating JNK signaling pathway / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the signaling pathways involved in β-arrestin1-induced proliferation of K562 cells.</p><p><b>METHODS</b>We established stable cell lines K562-siβ1 and K562-β1 by lentivirus-mediated β-arrestin1 knock-down or overexpression in K562 cells, with cells transfected with non-specific siRNA as the control (K562-Ctrl). The proliferation of these cells were evaluated by cell counting and CCK-8 assays. Western blotting was used to detect the expression of JNK and p-JNK in the cells, and co-immunoprecipitation (Co-IP) assay was employed to investigate the interaction between β-arrestin1 and Src.</p><p><b>RESULTS</b>K562-β1 cells showed significantly greater but K562-siβ1 cells had significantly lower proliferation ability and cell survival rate than K562-Ctrl cells. Western blotting showed that β-arrestin1 specifically enhanced the expression of p-JNK, and the JNK inhibitor SP600125 obviously suppressed p-JNK and cell proliferation of K562 cells. Co-IP assay revealed the binding of β-arrestin1 to Src.</p><p><b>CONCLUSIONS</b>In K562 cells, β-arrestin1 activates JNK signaling pathway by binding to Src to promote the cell proliferation.</p>

Role of DOR-β-arrestin1-Bcl2 signal transduction pathway and intervention effects of oxymatrine in ulcerative colitis / 华中科技大学学报（医学）（英德文版）

This study was aimed to investigate the role of the delta-opioid receptor (DOR)-β-arrestin1-Bcl-2 signal transduction pathway in the pathogenesis of ulcerative colitis (UC) and the intervention effects of oxymatrine on UC. Forty Sprague-Dawley rats were divided into normal group, model group, oxymatrine-treated group and mesalazine-treated group (n=10 each) at random. The rat UC model was established by intra-colonic injection of trinitrobenzene sulfonic acid in the model group and two treatment groups. The rats in oxymatrine-treated group were subjected to intramuscular injection of oxymatrine [63 mg/(kg·day)] for 15 days, and those in mesalazine-treated group given mesalazine solution [0.5 g/(kg·day)] by gastric lavage for the same days. Animals in normal group and model group were administered 3 mL water by gastric lavage for 15 days. On the 16th day, after fasting for 24 h, the rats were sacrificed for the removal of colon tissues. The expression levels of DOR, β-arrestin1 and Bcl-2 were determined in colon tissues by immunohistochemistry and real-time quantitative polymerase chain reaction (RT-PCR), respectively. It was found that the expression levels of DOR, β-arrestin1 and Bcl-2 protein and mRNA were significantly increased in the model group as compared with the other groups (P<0.05). They were conspicuously decreased in both mesalazine-treated and oxymatrine-treated groups in contrast to the model group (P<0.05). No statistically significant difference was noted in these indices between mesalazine- and oxymatrinetreated groups (P>0.05). This study indicated that the DOR-β-arrestin1-Bcl-2 signal transduction pathway may participate in the pathogenesis of UC. Moreover, oxymatrine can attenuate the development of UC by regulating the DOR-β-arrestin1-Bcl-2 signal transduction pathway.

Effects of Chinese Fructus Mume formula and its separated prescription extract on insulin resistance in type 2 diabetic rats / 华中科技大学学报（医学）（英德文版）

The effect of Fructus Mume formula and its separated prescription extract on insulin resistance in type 2 diabetic rats was investigated. The rat model of type 2 diabetes was established by feeding on a high-fat diet for 8 weeks and by subsequently intravenous injection of small doses of streptozotocin. Rats in treatment groups, including the Fructus Mume formula treatment group (FM), the cold property herbs of Fructus Mume formula treatment group (CFM), the warm property herbs of Fructus Mume formula treatment group (WFM), were administrated with Fructus Mume formula and its separated prescription extract by gavage, while the rats in diabetic model group (DM) and metformin group (MET) were given by gavage with normal saline and metformin correspondingly. The body weight before and after treatment was measured, and the oral glucose tolerance test (OGTT) and the insulin release test (IRT) were performed. The homeostasis model assessment-insulin resistance index (HOMA-IR) was calculated. The protein and mRNA expression levels of Insr, β-arrestin-2, Irs-1 and Glut-4 in the liver, skeletal muscle and fat tissues were detected by using Western blotting and RT-PCR respectively. The results demonstrated that, as compared with DM group, OGTT, IRT (0 h, 1 h) levels and HOMR-IR in treatment groups were all reduced, meanwhile their protein and mRNA expression levels of Insr, Irs-1 and Glut-4 in the liver, skeletal muscle and fat tissues were obviously increased, and their protein and mRNA expression levels of β-arrestin-2 in the liver and skeletal muscle tissues were also markedly increased. It was suggested that the Fructus Mume formula and its separated prescription extracts could effectively improve insulin resistance in type 2 diabetic rats, which might be related to the up-regulated expression of Insr, Irs-1 and Glut-4 in the liver, skeletal muscle and fat tissues, and β-arrestin-2 in the liver and skeletal muscle tissues.

β-arrestin2 plays a critical role in reward behaviors induced by cocaine / 生理学报

Besides its role in desensitization and internalization of receptors, β-arrestin2 facilitates G protein-independent signaling through its ability to scaffold various signaling molecules. β-arrestin2 is widely distributed in the central nervous system, and mediates signal transduction of brain circuit. The aim of the present study was to investigate the role of β-arrestin2 in reward behaviors induced by cocaine. We assessed the conditioned place preference (CPP) induced by low (10 mg/kg), moderate (20 mg/kg) and high (30 mg/kg) doses of cocaine in Arrb2(-/-) mice and Arrb2(+/+) controls. In the Arrb2(-/-) mice, moderate and high, but not low, dose of cocaine induced pronounced increases of CPP scores, which were higher than those in the Arrb2(+/+) mice. Moreover, cocaine-induced locomotor activity was significantly lower in Arrb2(-/-) mice than that of Arrb2(+/+) littermate controls. Taken together, our results suggest a potential role of β-arrestin2 in the cocaine-induced rewarding behaviors.

Role of β2-adrenoceptor-β-arrestin2-nuclear factor-κB signal transduction pathway and intervention effects of oxymatrine in ulcerative colitis / 中国结合医学杂志

<p><b>OBJECTIVE</b>To investigate the β2-adrenoceptor (β2AR)-β-arrestin2-nuclear factor-κB (NF-κB) signal transduction pathway and the intervention effects of oxymatrine in a rat model of ulcerative colitis.</p><p><b>METHODS</b>Forty SD rats were randomly divided into four groups, which included the normal control group, the model group, the mesalazine group and the oxymatrine treatment group, with 10 rats per group. Experimental colitis induced with trinitrobenzene sulfonic acid (TNBS) was established in each group except the normal control group. The rats in the oxymatrine treatment group were treated with intramuscular injection of oxymatrine 63 mg/(kg·d) for 15 days and the rats in the mesalazine group were treated with mesalazine solution 0.5 g/(kg·d) by gastric lavage for 15 days. The rats in the normal control group and model group were treated with 3 mL water by gastric lavage for 15 days. Diarrhea and bloody stool were carefully observed. Histological changes in colonic tissue were examined on day 7 in 2 rats per group that were randomly selected. The expression of β2AR, β-arrestin2 and NF-κB p65 in colon tissue and spleen lymphocytes were detected with immunohistochemistry and Western immunoblotting techniques on day 16 after fasting for 24 h. Six rats died of lavage with 2 each in the normal control, the model group and the mesalazine group; and were not included in the analysis.</p><p><b>RESULTS</b>The rats in the model group suffered from looser stool and bloody purulent stool after modeling. But in the oxymatrine and mesalazine groups, looser stool and bloody purulent stool reduced after treatment. And the colonic wall in the model group was thickened and the colon length shortened. The colon mucosa was congested in multiple areas with edema, erosion, superficial or linear ulcer and scar formation, while the intestinal mucosa injury reduced in the mesalazine and oxymatrine groups (P<0.01). In colonic mucosa and in spleen lymphocytes, compared with the normal control group, the expression of NF-κBp65 were significantly increased (P<0.01) in the model group while the expressions of β 2AR and β-arrestin2 were significantly decreased (P<0.01). Compared with the model group, the expression of NF-κ Bp65 was significantly decreased in the mesalazine group (P<0.01) and oxymatrine treatment group (P<0.01) while the expressions of β2AR and β-arrestin2 were significantly increased (P<0.01). There were no statistically significant differences in the expression of β2AR, β-arrestin2 and NF-κBp65 between the mesalazine group and oxymatrine group (P>0.05).</p><p><b>CONCLUSIONS</b>The β2AR-β-arrestin2-NF-κB signal transduction pathway participated in the pathologic course of ulcerative colitis. Oxymatrine attenuated ulcerative colitis through regulating the β2AR-β-arrestin2-NF-κB signal transduction pathway.</p>

Parkinson disease drug screening based on the interaction between D(2) dopamine receptor and beta-arrestin 2 detected by capillary zone electrophoresis

Parkinson's disease is the second most common neurodegenerative disease in the world. Beta-arrestin-2 has been reported to be an important protein involved in D(2) dopamine receptor desensitization, which is essential to Parkinson's disease. Moreover, the potential value of pharmacological inactivation of G protein-coupled receptor kinase or arrestin in the treatment of patients with Parkinson's disease has recently been shown. We studied the interaction between D(2) dopamine receptor and beta-arrestin-2 and the pharmacological regulation of chemical compounds on such interaction using capillary zone electrophoresis. The results from screening more than 40 compounds revealed three compounds that remarkably inhibit the beta-arrestin-2/D(2) dopamine receptor interaction among them. These compounds are promising therapies for Parkinson's disease, and the method used in this study has great potential for application in large-scale drug screening and evaluation.

Beta-arrestin and NF-kappaB, AP-1 activity in peripheral blood mononuclear cells of guinea pigs sensitized by trichloroethylene / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To explore the regulatory mechanism of immune response of guinea pigs sensitized by trichloroethylene (TCE), and the expression level of 3-arrestin, and the activity of NF-kappaB and AP-1 in peripheral blood mononuclear cells (PBMC) of guinea pigs sensitized by TCE.</p><p><b>METHODS</b>Guinea pigs were treated with TCE based on the guinea pig maximum response test (GPMT); Blank control group and DNCB positive control group were established. Scores of skin reaction were evaluated and used to determine whether or not allergy in guinea pig. Then TCE treated group was divided into sensitized group or un-sensitized group. The expression levels of beta-arrestin protein, activity of NF-kappaB and AP-1 in PBMC were detected by Western Blotting and EMSA, respectively. TNF-alpha level in serum was detected by ELISA kits.</p><p><b>RESULTS</b>No erythema or edema was found in the control group; part of guinea pigs treated with TCE developed erythema and edema, while obvious erythema and edema could be found in DNCB group. The sensitization rates were 71.4% and 100% in TCE and DNCB group, respectively. Compared with TCE un-sensitized group, expression of beta-arrestin and AP-1 activity were not significantly different in TCE sensitized group (P > 0.05). While the NF-kappaB activity was elevated obviously (P < 0.05). Compared with blank control groups [(32.118 +/- 12.550) pg/ml], serum TNF-alpha levels in TCE sensitized groups [(55.485 +/- 8.732) pg/ml] significantly elevated (P < 0.05);</p><p><b>CONCLUSION</b>In guinea pigs, beta-arrestin and AP-1 may not be activated, while the NF-kappaB activation is significant, and plays a immune regulatory role in the immune reaction of allergy induced by TCE.</p>

Pathogenetic mechanism of beta-arrestin1 in experimental colitis of rats and intervention effects of oxymatrine / 中国中西医结合杂志

<p><b>OBJECTIVE</b>To investigate the pathogenetic mechanism of beta-arrestin1 in the rat's experimental colitis, whether the delta opioid receptor-beta-arrestin1 -Bcl-2 signal transduction pathway involves the pathological process of experimental colitis in rats, and whether oxymatrine could attenuate colitis through this pathway.</p><p><b>METHODS</b>Twenty-six SD rats were randomly divided into four groups, the normal control group, the model group, the mesalazine treated group and the oxymatrine treated group (8 rats in the last group and 6 each in the others). The colitis model was established with trinitrobenzene sulfonic acid (TNBS), and rats in the latter two groups were treated by oxymatrine (intramuscular injection) and mesalazine (3 mL solution gavaged) for 15 days, respectively, while rats in the former two groups were fed with equal volume of distilled water. Symptoms of diarrhea and bloody stool as well as colonic patho-histologic changes were observed, and changes in expressions of delta opioid receptor, beta-arrestin1 and Bcl-2 in rat's colon tissue and spleen T lymphocytes were detected with immuno-histochemistry and Western immune-blotting techniques, respectively.</p><p><b>RESULTS</b>In contrast to the normal control group, expressions of delta opioid receptor, beta-arrestin1 and Bcl-2 were significantly higher in the model group (P < 0.01); compared with the model group, they were significantly lower in the two treated groups (P < 0.01).</p><p><b>CONCLUSIONS</b>Delta opioid receptor-beta-arrestin1 -Bcl-2 signal transduction pathway participates in the pathogenesis of TNBS-induced experimental colitis in rats. Oxymatrine can intervene the signal transduction, which may be one of the mechanisms of oxymatrine in attenuating colitis in rats.</p>