Activation of G-protein-coupled receptor 39 reduces neuropathic pain in a rat model

Activated G-protein-coupled receptor 39(GPR39)has been shown to attenuate inflammation by interacting with sirtuin 1(SIRT1)and peroxisome proliferator-activated receptor-γcoactivator 1α(PGC-1α).However,whether GPR39 attenuates neuropathic pain remains unclear.In this study,we established a Sprague-Dawley rat model of spared nerve injury-induced neuropathic pain and found that GPR39 expression was significantly decreased in neurons and microglia in the spinal dorsal horn compared with sham-operated rats.Intrathecal injection of TC-G 1008,a specific agonist of GPR39,significantly alleviated mechanical allodynia in the rats with spared nerve injury,improved spinal cord mitochondrial biogenesis,and alleviated neuroinflammation.These changes were abolished by GPR39 small interfering RNA(siRNA),Ex-527(SIRT1 inhibitor),and PGC-1αsiRNA.Taken together,these findings show that GPR39 activation ameliorates mechanical allodynia by activating the SIRT1/PGC-1αpathway in rats with spared nerve injury.

MicroRNA-760 acts as a tumor suppressor in gastric cancer development via inhibiting G-protein-coupled receptor kinase interacting protein-1 transcription

BACKGROUND Gastric cancer(GC)has become a serious threat to people's health.Accumulative evidence reveals that dysregulation of numerous microRNAs(miRNAs)has been found during malignant formation.So far,the role of microRNA-760(miR-760)in the development of GC is largely unknown.AIM To measure the expression level of miR-760 in GC and investigate its role in gastric tumorigenesis.METHODS Real-time quantitative polymerase chain reaction and Western blot analysis were used to measure the expression of miR-760 and G-protein-coupled receptor kinase interacting protein-1(GIT1).Cell growth was detected by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide(MTT)and cell colony formation assays.Apoptosis was assessed by flow cytometric analysis.The relationship between miR-760 and GIT1 was verified by luciferase reporter assay.RESULTS The results showed that the expression of miR-760 was decreased in GC and associated with poor clinical outcomes in GC patients.Furthermore,miR-760 restrained cell proliferation and cell colony formation and induced apoptosis in GC cells.In addition,miR-760 directly targeted GIT1 and negatively regulated its expression in GC.GIT1 was upregulated in GC and predicted a worse prognosis in GC patients.We also found that upregulation of GIT1 weakened the inhibitory CONCLUSION In conclusion,miR-760 targets GIT1 to inhibit cell growth and promote apoptosis in GC cells.Our data demonstrate that miR-760 may be a potential target for the treatment of GC.

G-protein-coupled estrogen receptor as a new therapeutic target for treating coronary artery disease

Coronary heart disease(CHD) continues to be the greatest mortality risk factor in the developed world. Estrogens are recognized to have great therapeutic potential to treat CHD and other cardiovascular diseases; however,a significant array of potentially debilitating side effects continues to limit their use. Moreover,recent clinical trials have indicated that long-term postmenopausal estrogen therapy may actually be detrimental to cardiovascular health. An exciting new development is the finding that the more recently discovered G-protein-coupled estrogen receptor(GPER) is expressed in coronary arteries-both in coronary endothelium and in smooth muscle within the vascular wall. Accumulating evidence indicates that GPER activation dilates coronary arteries and can also inhibit the prolif-eration and migration of coronary smooth muscle cells. Thus,selective GPER activation has the potential to increase coronary blood flow and possibly limit the debilitating consequences of coronary atherosclerotic disease. This review will highlight what is currently known regarding the impact of GPER activation on coronary arteries and the potential signaling mechanisms stimulated by GPER agonists in these vessels. A thorough understanding of GPER function in coronary arteries may promote the development of new therapies that would help alleviate CHD,while limiting the potentially dangerous side effects of estrogen therapy.

Mechanisms of regulation and function of G-protein-coupled receptor kinases

G-protein-coupled receptor kinases (GRKs) interact with the agonist-activated form of G-protein-coupled receptor (GPCR) to affect receptor phosphorylation and to initiate profound impairment of receptor signaling, or desensitization. GPCR forms the largest family of cell surface receptors, and defects in GRK function have the potential consequence to affect GPCR-stimulated biological responses in many pathological situations.

Desensitization of G-protein-coupled receptors induces vascular hypocontractility in response to norepinephrine in the mesenteric arteries of cirrhotic patients and rats

BACKGROUND: The increased β-arrestin-2 and its combination with G-protein-coupled receptors (GPCRs) lead to GPCRs desensitization. The latter may be responsible for decreased contractile reactivity in the mesenteric arteries of cirrhotic patients and rats. The present study is to investigate the machinery changes of α-adrenergic receptors and G proteins and their roles in the contractility of mesenteric arteries of cirrhotic patients and animal models. METHODS: Patients with cirrhosis due to hepatitis B and cirrhotic rats induced by CCl 4 were studied. Mesenteric artery contractility in response to norepinephrine was determined by a vessel perfusion system. The contractile effect of G protein-coupled receptor kinase-2 (GRK-2) inhibitor on the mesenteric artery was evaluated. The protein expression of the α 1 adrenergic receptor, G proteins, β-arrestin-2, GRK-2 as well as the activity of Rho associated coiled-coil forming protein kinase-1 (ROCK-1) were measured by Western blot. In addition, the interaction of α 1 adrenergic receptor with β-arrestin-2 was assessed by co-immunoprecipitation. RESULTS: The portal vein pressure of cirrhotic patients and rats was significantly higher than that of controls. The doseresponse curve to norepinephrine in mesenteric arteriole was shifted to the right, and EC 50 was significantly increased in cirrhotic patients and rats. There were no significant differences in the expressions of the α 1 adrenergic receptor and G proteins in the cirrhotic group compared with the controls. However, the protein expressions of GRK-2 and β-arrestin-2 were significantly elevated in cirrhotic patients and rats compared with those of the controls. The interaction of the α 1 adrenergic receptor and β-arrestin-2 was significantly aggravated. This interaction was significantly reversed by GRK-2 inhibitor. Both the protein expression and activity of ROCK-1 were significantly decreased in the mesenteric artery in patients with cirrhosis compared with those of the controls, and this phenomenon was not shown in the cirrhotic rats. Norepinephrine significantly increased the activity of ROCK-1 in normal rats but not in cirrhotic ones. Norepinephrine significantly increased ROCK-1 activity in cirrhotic rats when GRK-2 inhibitor was used. CONCLUSIONS: β-arrestin-2 expression and its interaction with GPCRs are significantly upregulated in the mesenteric arteries in patients and rats with cirrhosis. These upregulations result in GPCR desensitization, G-protein dysfunction and ROCK inhibition. These may explain the decreased contractility of the mesenteric artery in response to vasoconstrictors.

GPCR-Gs mediates the protective effects of ginsenoside Rb1 against oxygen-glucose deprivation/re-oxygenation-induced astrocyte injury

Objectives:To investigate whether the protective actions of ginsenoside Rb1(Rb1)on astrocytes are mediated through the G_(s)-type G-protein-coupled receptor(GPCR-G_(s)).Methods:Primary astrocyte cultures derived from neonatal mouse brain were used.Astrocyte injury was induced via oxygen-glucose deprivation/re-oxygenation(OGD/R).Cell morphology,viability,lactate dehydrogenase(LDH)leakage,apoptosis,glutamate uptake,and brain-derived neurotrophic factor(BDNF)secretion were assessed to gauge cell survival and functionality.Western blot was used to investigate the cyclic adenosine monophosphate(cAMP)and protein kinase B(Akt)signaling pathways.GPCR-G_(s)-specific inhibitors and molecular docking were used to identify target receptors.Results:Rb1 at concentrations ranging from 0.8 to 5μM did not significantly affect the viability,glutamate uptake,or BDNF secretion in normal astrocytes.OGD/R reduced astrocyte viability,increasing their LDH leakage and apoptosis rate.It also decreased glutamate uptake and BDNF secretion by these cells.Rb1 had protective effects of astrocytes challenged by OGD/R,by improving viability,reducing apoptosis,and enhancing glutamate uptake and BDNF secretion.Additionally,Rb1 activated the cAMP and Akt pathways in these cells.When the GPCR-G_(s) inhibitor NF449 was introduced,the protective effects of Rb1 completely disappeared,and its activation of cAMP and Akt signaling pathways was significantly inhibited.Conclusion:Rb1 protects against astrocytes from OGD/R-induced injury through GPCR-G_(s) mediation.

GPCR二聚体结构及功能

G蛋白偶联受体(G-protein coupled receptor,GPCR)是最广泛表达的膜蛋白家族之一,其可接收胞外信号刺激,通过自身构象变化激活胞内G蛋白等一系列信号通路,参与众多生理调节过程,具有重要的功能,因此其也是重要的药物靶点。GPCR二聚化是调控其功能的重要形式之一,靶向GPCR二聚体开发药物是药物研发的一个新方向。越来越多的研究报道了GPCR二聚化及其结构与功能调控的机制,本文综述了GPCR二聚体结构及功能的研究进展,为了解GPCR二聚体的发现、二聚化方式、功能调控机制,及进一步靶向GPCR二聚体药物开发提供了研究基础。

Role of doublecortin-like kinase 1 and leucine-rich repeat-containing G-protein-coupled receptor 5 in patients with stage Ⅱ/Ⅲ colorectal cancer:Cancer progression and prognosis

BACKGROUND Cancer stem cells(CSCs)are a subpopulation of cancer cells with the potential of self-renewal and differentiation.CSCs play critical roles in tumorigenesis,recurrence,metastasis,radiation tolerance and chemoresistance.AIM To assess the expression patterns and clinical potential of doublecortin-like kinase 1(DCLK1)and leucine-rich repeat-containing G-protein-coupled receptor 5(Lgr5),as prognostic CSC markers of colorectal cancer(CRC).METHODS The expression of DCLK1 and Lgr5 in CRC tissue sections from 92 patients was determined by immunohistochemistry.Each case was evaluated using a combined scoring method based on signal intensity staining(scored 0-3)and the proportion of positively stained cancer cells(scored 0-3).The final staining score was calculated as the intensity score multiplied by the proportion score.Low expression of DCLK1 and Lgr5 was defined as a score of 0-3;high expression of DCLK1 and Lgr5 was defined as a score of≥4.Specimens were categorized as either high or low expression,and the correlation between the expression of DCLK1 or Lgr5 and clinicopathological factors was investigated.RESULTS DCLK1 and Lgr5 expression levels were significantly positively correlated.CRC patients with high DCLK1,Lgr5 and DCLK1/Lgr5 expressions had poorer progression-free survival and overall survival.Moreover,high expression of DCLK1 was an independent prognostic factor for recurrence and overall survival in patients with CRC by multivariate analysis(P=0.026 and P=0.049,respectively).CONCLUSION DCLK1 may be a potential CSC marker for the recurrence and survival of CRC patients.

利用深度迁移学习靶向GPCRs的配体活性预测

G蛋白偶联受体(GPCRs)是最重要的药物靶标之一,约占市场上药物靶标的34%。药物发现过程中,配体生物活性的准确建模和解释对于筛选苗头化合物至关重要。研究表明,同源的G蛋白偶联受体能提升配体分子生物活性的预测性能和可解释性。提出了一种新的方法GLEM,用多任务下的深度迁移学习来预测配体的生物活性,并通过组稀疏来识别相关的关键子结构。GLEM方法在9组30个具有代表性的人类GPCR数据集上进行了实验,这些GPCRs涵盖了大部分人类GPCRs的子家族,每个GPCR数据集都包含60~3000个配体。实验结果表明,GLEM方法在绝大多数数据集中都获得了最好的性能。与单任务学习方法相比,GLEM方法在r2上平均提升了31.72%;与深度学习方法相比,GLEM方法在r2上平均提升了22.45%。此外,还评估了不同数量的训练样本对模型性能的影响,实验发现GLEM方法在小样本情况下表现最好。

Peripheral actions and direct central-local communications of melanocortin 4 receptor signaling

Melanocortin 4 receptor(MC4R),the most important monogenetic cause of human metabolic disorders,has been of great interest to many researchers in the field of energy homeostasis and public health.Because MC4R is a vital pharmaceutical target for maintaining controllable appetite and body weight for professional athletes,previous studies have mainly focused on the central,rather than the peripheral,roles of MC4R.Thus,the local expression of MC4R and its behavioral regulation remain unclear.In an attempt to shed light on different directions for future studies of MC4R signaling,we review a series of recent and important studies exploring the peripheral functions of MC4R and the direct physiological interaction between peripheral organs and central MC4R neurons in this article.

Fluorescence Resonance Energy Transfer Competitive Binding Assay for Secretin Receptor （Class B-GPCR）

Human secretin is responsible for carrying a number of physiological functions including energy and water homeostasis, thus making secretin receptor a promising target for drug development. For GPCRs （G protein-coupled receptors）, radioactive ligands are usually used in conventional binding assays to characterize the binding affinities of the ligands. An alternative non-hazardous fluorescence based binding assay is lucrative over the radio-ligand assays. Here, we have developed a FRET （fluorescence resonance energy transfer） competitive binding assay for human secretin receptor. The receptor gene sequence is cloned in the SNAP （single nucleotide amplified polymorphisms） tag-plasmid and expressed in CHO （chinese hamster ovary）-K1 cells. Its expression and function is confirmed with immunofluorescence localization and receptor activation. The receptor and the ligand are labeled with fluorescent donor （Tb） and acceptor （Alexa488）. FRET signals are produced when the labeled ligand is bound to the receptor and the same drop when it is displaced by the test compounds. The saturation concentration of the receptor labeling is 100 nM, and the ligand Kd value is 500 nM. At these concentrations, the IC50 of unlabeled secretin is 1.63 4- 3.55 nM. Additionally, few class-B ligands are screened and hold good correlation with traditional radio-ligand assay. Henceforth, this FRET binding assay can be efficiently used as a primary screening tool for peptide analogs.

β-Arrestins参与GPCRs信号通路的分子机制

β-抑制蛋白(β-arrestins)是一类在β肾上腺素受体激酶(βARK)提纯过程中发现的重要支架蛋白和信号调控因子;G蛋白偶联受体(GPCRs)为7次跨膜受体,在细胞信号转导中发挥关键作用,是很多临床药物的作用靶点.β-抑制蛋白作为衔接蛋白,调控GPCRs相关的信号通路,介导GPCRs的脱敏、内化、循环、复敏等生理过程,影响多种疾病的进程.本文总结了β-抑制蛋白参与GPCRs信号通路的研究进展,侧重阐明了其中的分子机制,以期为开发新一代调控GPCRs功能活性的相关药物提供理论基础.

基于多视图矩阵补全的蛋白受体功能预测

蛋白受体是细胞信号转导的重要组成部分,也是人类最重要的药物靶点,其中G蛋白偶联受体(G Protein Coupled Receptors,GPCRs)占绝大部分,目前市场上大约34%的药物都以GPCRs作为靶点.准确地注释GPCR蛋白的生物学功能对于理解它们涉及的生理过程及靶向药物发现至关重要,其中基因本体学(Gene Ontology,GO)是描述蛋白质功能最常用的方式,GPCR蛋白和GO都包含多个视图信息,有效利用这些信息可有效提升蛋白质功能的预测性能.因此,提出一种基于多视图的归纳矩阵补全方法MVIMC(Multi-View Inductive Matrix Completion)来预测GPCR蛋白的GO生物学功能.MVIMC有效利用了GPCR蛋白和GO标记视图信息,其中GPCR包含文本信息和结构域信息,GO包含文本信息.实验结果表明,MVIMC在分子功能和生物过程两方面的预测概率分别达到68%和69%,优于目前最好的矩阵补全方法以及CAFA蛋白质功能预测比赛中的常用方法.

趋化素受体的研究进展

趋化素受体是G蛋白偶联受体(G Protein-Coupled Receptors,GPCRs)家族的重要成员,广泛分布于人体各组织器官中,参与炎症反应、血管生成、脂质和葡萄糖代谢等多种生理过程,与炎症性疾病、癌症、代谢综合征等多种疾病的发生发展密切相关。本文综述了趋化素受体家族的结构、信号转导特性、相关疾病和拮抗剂类药物开发的最新研究进展,以期为后续研究趋化素受体功能和开发新型药物提供思路和参考。

稻瘟病菌cAMP受体类GPCR的生物信息学分析

G蛋白偶联受体(GPCRs)是一类重要的细胞表面受体,通过G蛋白介导着多种生物学途径,其介导的信号转导机制及其作为药物靶标的研究已成为研究热点之一。运用生物信息学的方法,对稻瘟病菌全基因组序列中可能的cAMP类GPCR基因进行了生物信息学分析,为深入研究cAMP类GPCR基因的结构和生物学功能奠定了基础。

醛固酮瘤(APA)发病相关的G蛋白耦联受体(GPCRs)研究进展

醛固酮瘤（aldosterone-producing adenoma,APA）是原发性醛固酮增多症的一个重要亚型,约占30％～60％,是引起继发性高血压的重要病因.有关APA的发病机制,可见不同水平与角度的研究,但是对于APA的具体发病机制仍不清楚.本文就已知的与发病相关的G蛋白耦联受体（G-protein-coupled receptors,GPCRs）进行论述.

Conformational dynamics in GPCR signaling by NMR

G-protein-coupled receptors(GPCRs)mediate a wide range of cellular responses to various ligands or stimuli,and are the most important drug targets associated with human diseases.While major advances in GPCR structural biology have greatly deepened our understanding of its activation mechanism,the highly complex changes in the structural dynamics of GPCRs during activation remain underdetermined and their links to physiological functions largely unknown.Solution nuclear magnetic resonance(NMR)spectroscopy is an essential technique that allows the characterization of protein structural dynamics at atomic level,and has been applied in the studies of GPCR structural-function relationship in the past decade.Herein,we summarize a few specific studies in which solution NMR methods were employed and provided novel insights into questions difficult to be addressed by other methods.

Activation of β_2-Adrenergic Receptor Induced by Three Catecholamine Agonists:a Docking and Molecular Dynamics Study

We studied the activation of β2-adrenergic receptor（β2AR） by norepinephrine, epinephrine and isoprote- renol using docking and molecular dynamics（MD） simulation. The simulation was done on the assumption that β2AR was surrounded with explicit water and infinite lipid bilayer membrane at body temperature. So the result should be close to that under the physiological conditions. We calculated the structure of binding sites in β2AR for the three ac- tivators. We also simulated the change of the conformation ofβ2AR in the transmembrane regions（TMs）, in the mo- lecular switches, and in the conserved DRY（Aspartic acid, Arginine and Tyrosine） motif. This study provides detailed information concerning the structure ofβ2AR during activation process.

Effect of organophosphorus insecticides on phosphorylation of the M_2 muscarinic acetylcholine receptor

BACKGROUND： Organophosphorus insecticides may promote the accumulation of acetylcholine at synapses and the neuromuscular junction by inhibiting acetylcholinesterase activity to cause disturbance of neural signal conduction and induce a toxic reaction. Organophosphorus insecticides may act on M2 muscarinic acetylcholine receptors, whose combination with G proteins is regulated by phosphorylation of G protein-coupled receptor kinase 2. OBJECTIVE： To investigate the effects of organophosphorus insecticides on the phosphorylation of G protein-coupled receptor kinase 2-mediated M2 muscarinic acetylcholine receptors and to reveal other possible actions of organophosphorus insecticides. DESIGN, TIME AND SETTING： An observational study, which was performed in the Central Laboratory of Shenyang Medical College, and Department of Physiological Sciences, College of Veterinary Medicine, Oklahoma State University from June 2002 to December 2004. MATERIALS： Paraoxon, parathion, chlorpyrifos, and chlorpyrifos oxon were provided by Chem Service Company, USA, [γ -p^32] ATP and [^35S]GTP γ S by New England Nuclear Life Science Products, and recombinant β 2-adrenergic receptor membrane protein by Sigma Company, USA. METHODS： The M2 muscarinic acetylcholine receptor was extracted and purified from pig brain using affinity chromatography. Subsequently, the purified M2 muscarinic acetylcholine receptor, G protein-coupled receptor kinase 2, and [γ -p^32] ATP were incubated with different concentrations of paraoxon and chlorpyrifos oxon together. The mixture then underwent polyacrylamide gel electrophoresis, and the gel film was dried and radioactively autographed to detect phosphorylation of the M2 muscarinic acetylcholine receptor. Finally, the radio-labeled phosphorylated M2 receptor protein band was excised for counting with an isotope liquid scintillation counter. MAIN OUTCOME MEASURES： Effects of chlorpyrifos oxon, paraoxon, chlorpyrifos, and parathion in different concentrations on the phosphorylation of the M2 muscarinic acetylcholine receptor; effects of chlorpyrifos oxon on the phosphorylation of the β -adrenergic receptor. RESULTS： Chlorpyrifos oxon could completely inhibit the phosphorylation of the M2 muscarinic acetylcholine receptor, and its IC50 was 70 μ mol/L. Chlorpyrifos could also inhibit the phosphorylation of the M2 muscarinic acetylcholine receptor. However, paraoxon and parathion could not inhibit the phosphorylation of the M2 muscarinic acetylcholine receptor. Chlorpyrifos oxon in different concentrations could also not inhibit the phosphorylation of the β 2-adrenergic receptor catalyzed by G protein-coupled receptor kinase 2. CONCLUSION： Different kinds of organophosphorus insecticides have different effects on the phosphorylation of the G protein-coupled receptor kinase 2-mediated M2 muscarinic acetylcholine receptor. Organophosphorus insecticides possibly have different toxic effects.

Molecular regulation of calcium-sensing receptor(CaSR)-mediated signaling

Calcium-sensing receptor(CaSR),a family C G-protein-coupled receptor,plays a crucial role in regulating calcium homeostasis by sensing small concentration changes of extracellular Ca^(2+),Mg^(2+),amino acids(e.g.,L-Trp and L-Phe),small peptides,anions(e.g.,HCO_(3)^(-)and PO_(4)^(3-)),and pH.CaSR-mediated intracellular Ca^(2+)signaling regulates a diverse set of cellular processes including gene transcription,cell proliferation,differentiation,apoptosis,muscle contraction,and neuronal transmission.Dysfunction of CaSR with mutations results in diseases such as autosomal dominant hypocalcemia,familial hypocalciuric hypercalcemia,and neonatal severe hyperparathyroidism.CaSR also influences calciotropic disorders,such as osteoporosis,and noncalciotropic disorders,such as cancer,Alzheimer's disease,and pulmonary arterial hypertension.This study first reviews recent advances in biochemical and structural determination of the framework of CaSR and its interaction sites with natural ligands,as well as exogenous positive allosteric modulators and negative allosteric modulators.The establishment of the first CaSR protein-protein interactome network revealed 94 novel players involved in protein processing in endoplasmic reticulum,trafficking,cell surface expression,endocytosis,degradation,and signaling pathways.The roles of these proteins in Ca^(2+)-dependent cellular physiological processes and in CaSR-dependent cellular signaling provide new insights into the molecular basis of diseases caused by CaSR mutations and dysregulated CaSR activity caused by its protein interactors and facilitate the design of therapeutic agents that target CaSR and other family C G-protein-coupled receptors.