G-protein coupled receptors and synaptic plasticity in sleep deprivation

Insufficient sleep has been correlated to many physiological and psychoneurological disorders.Over the years,our understanding of the state of sleep has transcended from an inactive period of rest to a more active state involving important cellular and molecular processes.In addition,during sleep,electrophysiological changes also occur in pathways in specific regions of the mammalian central nervous system(CNS).Activity mediated synaptic plasticity in the CNS can lead to long-term and sometimes permanent strengthening and/or weakening synaptic strength affecting neuronal network behaviour.Memory consolidation and learning that take place during sleep cycles,can be affected by changes in synaptic plasticity during sleep disturbances.G-protein coupled receptors(GPCRs),with their versatile structural and functional attributes,can regulate synaptic plasticity in CNS and hence,may be potentially affected in sleep deprived conditions.In this review,we aim to discuss important functional changes that can take place in the CNS during sleep and sleep deprivation and how changes in GPCRs can lead to potential problems with therapeutics with pharmacological interventions.

Isoleucine, an Essential Amino Acid, Induces the Expression of Human <i>β</i>Defensin 2 through the Activation of the G-Protein Coupled Receptor-ERK Pathway in the Intestinal Epithelia

Anti-microbial peptides are essential for the intestinal innate immunity that protects the intestinal epithelia from attacks by foreign pathogens. Human β-defensin (HBD) is one of the pivotal anti-microbial peptides that are expressed in the colonic epithelia. This study investigated the effect and the signaling mechanism of inducible β-defensin HBD2 by an essential amino acid, isoleucine (Ile) in colonic epithelial cells. Here we examined the expression level of HBD2 on induction of Ile in epithelial cells, and checked this pathway. HBD2 mRNA was induced by co-incubation with IL-1α and Ile in Caco2 cells, but not by Ile alone. An inhibitor of either ERK or Gi, a subunit of G-proteins, reduced the induction of HBD2 mRNA by Ile. The treatment with Ile also increased the intracellular calcium ion concentration, thus suggesting that the GPCR and ERK signaling pathway mediate the effects of Ile. These results indicate that an essential amino acid, Ile, enhances the expression of an inducible β-defensin, namely HBD2, by IL-1α through the activation of GPCRs and ERK signaling pathway. The administration of Ile may therefore represent a possible option to safely treat intestinal inflammation.

New insights into sodium transport regulation in the distal nephron:Role of G-protein coupled receptors

The renal handling of Na^+ balance is a major determinant of the blood pressure(BP) level. The inability of the kidney to excrete the daily load of Na+ represents the primary cause of chronic hypertension. Among the different segments that constitute the nephron, those present in the distal part(i.e., the cortical thick ascending limb, the distal convoluted tubule, the connecting and collecting tubules) play a central role in the fine-tuning of renal Na^+ excretion and are the target of many different regulatory processes that modulate Na^+ retention more or less efficiently. G-protein coupled receptors(GPCRs) are crucially involved in this regulation and could represent efficient pharmacological targets to control BP levels. In this review, we describe both classical and novel GPCR-dependent regulatory systems that have been shown to modulate renal Na^+ absorption in the distal nephron. In addition to the multiplicity of the GPCR that regulate Na^+ excretion, this review also highlights the complexity of these different pathways, and the connections between them.

Insights into the structural biology of G-protein coupled receptors impacts drug design for central nervous system neurodegenerative processes

In the last few years, there have been important new insights into the structural biology of G-protein coupled receptors. It is now known that allosteric binding sites are involved in the affinity and selec- tivity of ligands for G-protein coupled receptors, and that signaling by these receptors involves both G-protein dependent and independent pathways. The present review outlines the physiological and pharmacological implications of this perspective for the design of new drugs to treat disorders of the central nervous system. Specifically, new possibilities are explored in relation to allosteric and or- thosteric binding sites on dopamine receptors for the treatment of Parkinson＇s disease, and on muscarinic receptors for Alzheimer＇s disease. Future research can seek to identify ligands that can bind to more than one site on the same receptor, or simultaneously bind to two receptors and form a dimer. For example, the design of bivalent drugs that can reach homo/hetero-dimers of D2 dopa- mine receptor holds promise as a relevant therapeutic strategy for Parkinson＇s disease. Regarding the treatment of Alzheimer＇s disease, the design of dualsteric ligands for mono-oligomeric mus- carinic receptors could increase therapeutic effectiveness by generating potent compounds that could activate more than one signaling pathway.

Association of hepatocyte-derived growth factor receptor/caudal type homeobox 2 co-expression with mucosal regeneration in active ulcerative colitis

AIM:To characterize the regeneration-associated stem cell-related phenotype of hepatocyte-derived growth factor receptor(HGFR)-expressing cells in active ulcerative colitis(UC).METHODS:On the whole 38 peripheral blood samples and 38 colonic biopsy samples from 18 patients with histologically proven active UC and 20 healthy control subjects were collected.After preparing tissue microarrays and blood smears HGFR,caudal type homeobox 2(CDX2),prominin-1(CD133) and Musashi-1conventional and double fluorescent immunolabelings were performed.Immunostained samples were digitalized using high-resolution Mirax Desk instrument,and analyzed with the Mirax TMA Module software.For semiquantitative counting of immunopositive lamina propria(LP) cells 5 fields of view were counted at magnification x 200 in each sample core,then mean ± SD were determined.In case of peripheral blood smears,30 fields of view with 100 μm diameter were evaluated in every sample and the number of immunopositive cells(mean ± SD) was determined.Using 337 nm UVA Laser MicroDissection system at least 5000 subepithelial cells from the lamina propria were collected.Gene expression analysis of HGFR,CDX2,CD133,leucine-rich repeat-containing G-protein coupled receptor 5(Lgr5),Musashi-1 and cytokeratin20(CK20) were performed in both laser-microdisscted samples and blood samples by using real time reverse transcription polymerase chain reaction(RT-PCR).RESULTS:By performing conventional and double fluorescent immunolabelings confirmed by RT-PCR,higher number of HGFR(blood:6.7 ± 1.22 vs 38.5 ±3.18;LP:2.25 ± 0.85 vs 9.22 ± 0.65;P < 0.05),CDX2(blood:0 vs 0.94 ± 0.64;LP:0.75 ± 0.55 vs 2.11± 0.75;P < 0.05),CD133(blood:1.1 ± 0.72 vs 8.3± 1.08;LP:11.1 ± 0.85 vs 26.28 ± 1.71;P < 0.05)and Musashi-1(blood and LP:0 vs scattered) positive cells were detected in blood and lamina propria of UC samples as compared to controls.HGFR/CDX2(blood:0 vs 1± 0.59;LP:0.8 ± 0.69 vs 2.06 ± 0.72,P < 0.05)and Musashi-1/CDX2(blood and LP:0 vs scattered) coexpressions were found in blood and lamina propria of UC samples.HGFR/CD133 and CD133/CDX2 coexpressions appeared only in UC lamina propria samples.CDX2,Lgr5 and Musashi-1 expressions in UC blood samples were not accompanied by CK20 mRNA expression.CONCLUSION:In active UC,a portion of circulating HGFR-expressing cells are committed to the epithelial lineage,and may participate in mucosal regeneration by undergoing mesenchymal-to-epithelial transition.

Identification of a key G-protein coupled receptor in mediating appressorium formation and fungal virulence against insects

Fungal G-protein coupled receptors(GPCRs)play essential roles in sensing environmental cues including host signals.The study of GPCR in mediating fungus-insect interactions is still limited.Here we report the evolution of GPCR genes encoded in the entomopathogenic Metarhizium species and found the expansion of Pth11-like GPCRs in the generalist species with a wide host range.By deletion of ten candidate genes MrGpr1–MrGpr10 selected from the six obtained subfamilies in the generalist M.robertsii,we found that each of them played a varied level of roles in mediating appressorium formation.In particular,deletion of MrGpr8 resulted in the failure of appressorium formation on different substrates and the loss of virulence during topical infection of insects but not during injection assays when compared with the wild-type(WT)strain.Further analysis revealed that disruption of MrGpr8 substantially impaired the nucleus translocation of the mitogen-activated protein kinase(MAPK)Mero-Fus3 but not the MAPK Mero-Slt2 during appressorium formation.We also found that the defect ofΔMrGpr8 could not be rescued with the addition of cyclic AMP for appressorium formation.Relative to the WT,differential expression of the selected genes have also been detected inΔMrGpr8.The results of this study may benefit the understanding of fungus-interactions mediated by GPCRs.

The complexity of G-protein coupled receptor-ligand interactions

The G-protein coupled receptors(GPCRs)play fundamental roles in the human biololgy and drug discovery.GPCRs function as signalling molecules that transduce extracellular signals into cells.The signalling transduction is generally triggered by interacting with ligands,including photons,ions,small organic compounds,peptides,proteins and lipids.In this review,we focus on interactions with diffusible ligands such as hormones and neurotransmitters.We discuss three aspects of the complexity of the GPCR-ligand interactions:functional selectivity of ligands,receptor subtype selectivity of ligands and orphan GPCRs.

Role of opioid receptor heterodimerization in pain modulation and tolerance development

Protein to protein interactions leading to homo/heteromerization of receptor is well documented in literature. These interactions leading to dimeric/oligomers formation of receptors are known to modulate their function, particularly in case of G-protein coupled receptors. The opioid receptor heteromers having changed pharmacological properties than the constituent protomers provides preferences for novel drug targets that could lead to potential analgesicactivity devoid of tolerance and physical dependence. Heterodimerization of opioid receptors appears to generate novel binding properties with improved specificity and lack of side effects. Further the molecules which can interact simultaneously to both the protomers of the heteromer, or to both the binding sites(orthosteric and allosteric) of a receptor protein could be potential therapeutic molecules. This review highlights the recent advancements in exploring the plausible role of heteromerization of opioid receptors in induction of tolerance free antinociception.

G protein-coupled receptors in energy homeostasis

G-protein coupled receptors(GPCRs)compromise the largest membrane protein superfamily which play vital roles in physiological and pathophysiological processes including energy homeostasis.Moreover,they also represent the up-to-date most successful drug target.The gut hormone GPCRs,such as glucagon receptor and GLP-1 receptor,have been intensively studied for their roles in metabolism and respective drugs have developed for the treatment of metabolic diseases such as type 2 diabetes(T2D).Along with the advances of biomedical research,more GPCRs have been found to play important roles in the regulation of energy homeostasis from nutrient sensing,appetite control to glucose and fatty acid metabolism with various mechanisms.The investigation of their biological functions will not only improve our understanding of how our body keeps the balance of energy intake and expenditure,but also highlight the possible drug targets for the treatment of metabolic diseases.The present review summarizes GPCRs involved in the energy control with special emphasis on their pathophysiological roles in metabolic diseases and hopefully triggers more intensive and systematic investigations in the field so that a comprehensive network control of energy homeostasis will be revealed,and better drugs will be developed in the foreseeable future.

结直肠癌组织中GPR15和HMGA1表达情况及其临床预后价值研究

目的探讨结直肠癌(CRC)组织中孤儿受体G蛋白偶联受体15(GPR15)和高迁移率族蛋白组A1(HMGA1)的表达情况及其临床预后价值。方法选取2019年1月至2020年1月于扬州大学附属医院接受根治性手术治疗的89例CRC患者,收集患者术中的CRC癌组织和癌旁组织。采用实时荧光定量聚合酶链式反应及免疫组化染色法检测组织中GPR15和HMGA1的表达情况,分析CRC癌组织中GPR15及HMGA1表达与患者临床病理特征的关联性。采用Kaplan-Meier法分析CRC癌组织中GPR15、HMGA1表达情况与患者生存预后的关联性。采用Cox回归分析CRC患者预后的影响因素。结果CRC癌组织中GPR15、HMGA1 mRNA相对表达量显著高于癌旁组织(P<0.05)。CRC癌组织中GPR15、HMGA1蛋白的阳性表达率显著高于癌旁组织(P<0.05)。TNM分期Ⅲ期、低分化程度及合并淋巴结转移的CRC癌组织中GPR15、HMGA1阳性表达率分别高于Ⅰ~Ⅱ期、高中分化程度及无淋巴结转移的CRC癌组织,差异有统计学意义(P<0.05)。GPR15阴性组生存预后显著优于阳性组(log-rank检验:χ^(2)=9.124,P=0.003);HMGA1阴性组生存预后显著优于阳性组(log-rank检验:χ^(2)=10.140,P=0.001)。肿瘤TNM分期Ⅲ期、低分化程度、合并淋巴结转移、GPR15阳性、HMGA1阳性是促进CRC患者不良预后的独立危险因素(P<0.05)。结论CRC癌组织中GPR15和HMGA1的表达水平升高,两者与CRC患者不良临床病理特征密切相关,可作为新的评估CRC患者预后的肿瘤标志物。

人源孤儿G蛋白偶联受体hGPCRc的分子克隆及其初步鉴定

孤儿G蛋白偶联受体 (orphanGprotein coupledreceptors ,oGPCRs)是最重要的潜在药物靶点 ,对于创新药物研究意义重大 .根据已有文献及相关基因数据库提供的信息 ,利用RT PCR从人结肠组织获得oGPCR某一成员的氨基酸编码序列 ,大小为 10 14bp ,而且与GenBank已登录序列(AB0 835 98)完全一致 ,称之为hGPCRc ;又用相同的引物以健康志愿者血液基因组DNA作为模板进行PCR扩增 ,亦得到同样大小的DNA序列 ,测序显示二者个别碱基不一致 ,但所对应氨基酸序列并无差异 .另外 ,RT PCR对人源部分组织及细胞系的检测结果显示 :hGPCRc在人脑组织表达最高 ,结肠次之 ,其它组织或细胞系如胃、血液、肝、肺、上皮未检测到该基因的表达 .利用相关软件对hGPCRc分别结果显示 :hGPCRc定位于人染色体 13q32 3,与小鼠、大鼠的对应物序列同源性高达85 % ,但与人源其他已知基因的同源性较低 ,对应的氨基酸序列组成了 7个跨膜区段的结构域 .因此 ,hGPCRc符合GPCR的结构特点 ,应为人类oGPCRs的新成员 .

孤儿G蛋白偶联受体hGPCRc的亚细胞定位及组织分布

利用相关生物信息学软件,对从人结肠组织克隆所得某一孤儿G蛋白偶联受体(orphanGprotein_coupledreceptors ,oGPCRs)成员hGPCRc的氨基酸序列进行分析显示,hGPCRc对应的氨基酸序列组成了七个跨膜区段的结构域,具备GPCR的结构特征;然后,将hGPCRc之cDNA与绿色荧光载体pEGFP_N1 构建GFP_hGPCRc表达载体,以空白质粒pEGFP_N1 作对照,转染CHO_K1 细胞,在激光扫描共聚焦显微镜下观察到空白质粒pEGFP_N1 转染的细胞表达了GFP并均匀分布于整个细胞,而GFP_hGPCRc转染的细胞观察到荧光清晰聚集于细胞膜和各细胞器质膜上,因而hGPCRc蛋白定位于膜上并稳定表达,与软件分析结果相一致;最后,以RT_PCR检测hGPCRc在2 0周龄胎儿重要组织器官及部分成人组织中的表达情况,结果显示hGPCRc在人心、肾、小脑及结肠等组织均有表达,但在肝、大脑、小肠及肌肉等组织里未检测到表达。该表达谱对于进一步认识hGPCRc在胚胎发育中的作用及生理功能提供了线索。

孤儿G蛋白偶联受体研究进展

孤儿G蛋白偶联受体的研究意味着发现其尚未了解的内源性配体 ,是后基因组时代功能基因组学研究的热点之一 ,对生命科学的发展具有深远的影响。本文介绍孤儿G蛋白偶联受体的概念。

Obestatin及其受体与胃肠动力

肥胖抑制素(Obestatin)是一个胃合成的由23个氨基酸组成的酰胺化的脑肠肽,他能够与孤儿G蛋白偶联受体GPR39结合,产生抑制摄食、减缓体质量增加、抑制胃排空和小肠收缩活动的生物学功能.Obestatin和Ghrelin是由同一条Ghrelin基因经翻译后加工修饰而行成的两条不同多肽,但Obestatin表现出与Ghrelin截然相反的生物学作用.然而,最近有研究怀疑以上发现的真实性.鉴于Obestatin可能不是GPR39的受体以及Obestatin对胃肠调节没有作用的争论,本文主要就Obestatin及其受体和Obestatin对胃肠动力的调节作用等相关研究成果作一概述.

生物信息学在孤儿G蛋白偶联受体配基筛选中的应用

生物信息学的飞速发展为孤儿G蛋白偶联受体(orphanGprotein-coupledreceptors,oGPCRs)配基的筛选提供了重要的信息资源。利用生物信息学数据库和工具对oGPCRs的核酸和蛋白质序列进行运算、分析、注释和预测,获得足够的生物信息,辅助实验研究,以尽可能快速、准确地筛选出oGPCRs的特异性配基。本文介绍有关生物信息学在oGPCRs配基筛选研究中的应用。

人源受体hGPCRc工程细胞株的建立及其应用

目的建立孤儿G蛋白偶联受体(OrphanGproteincoupledreceptors,oGPCRs)配基筛选体系并应用于化合物的筛选。方法利用RTPCR从人结肠组织获得oGPCR成员hGPCRc的氨基酸编码序列,在利用相关软件对hGPCRc的结构特点进行分析的基础上,构建hGPCRc之表达载体pcDNA3.1(+)hGPCRc,转染CHOK1细胞获得CHOhGPCR工程细胞株,将不同化合物作用于细胞株,用Fluo3为分子探针检测细胞内钙离子浓度变化,以分析化合物中是否为该受体的特异性配基。结果生物信息学分析得到:hGPCR定位于人染色体13q32.2,对应的氨基酸序列组成了7个跨膜区段的结构域,在进化树上与人源P2Y1受体最亲近,应属于人类GPCR成员;成功得到CHOhGPCRc工程细胞株;所检测化合物作用于细胞株并没有引起胞内钙离子的波动,很可能没有活化hGPCRc。结论hGPCRc是一个与已知人P2Y1最近的成员,但基于CHOhGPCRc工程细胞株的第二信使筛选结果表明,hGPCRc并不被P2Y1的已知配基活化因此很可能属于不同于P2Y1的嘌呤类受体新亚型。

GPCR-Gα融合蛋白及其在oGPCRs配基筛选中的应用

GPCRGα融合蛋白是近几年用于受体研究的新颖手段之一,它的表达确保了受体与G蛋白之间1∶1的化学计量关系、空间位置上的邻近性及适宜于高通量的配基筛选,使其为孤儿G蛋白偶联受体提供了一种新的研究策略,将在孤儿受体的配基筛选中发挥重要作用,对研发以oGPCR为作用靶点的新药产生积极意义。

人孤儿受体GPR81分子克隆、组织分布及表达工程细胞株的建立

采用PCR技术分别从人全血基因组DNA及引产胚胎肾组织cDNA中扩增得到gpr81的全长cDNA序列(1041bp),运用生物信息学手段绘制该基因的分子进化树,显示该基因的氨基酸序列与烟酸受体同源性最高;然后,采用RT-PCR法分析该基因表达的组织分布,组织表达谱显示该基因在多种组织均有表达,以心脏及肝脏组织为最高;利用分子克隆手段构建含6×组氨酸(His)标签蛋白的真核表达载体pcDNA3·1(-)/his-myc-A-gpr81,通过脂质体介导,将该重组质粒转染CHO-K1细胞,RT-PCR证实该基因已整合入CHO-K1细胞的基因组中,Western-blot表明GPR81在CHO-GPR81工程细胞株中有表达。组织表达谱的检测和工程细胞株的建立为进一步研究该受体的生物学功能奠定了基础。

心血管活性肽Apelin生物学功能研究进展

G蛋白偶联受体是指一大类与G蛋白偶联并参与和介导细胞外信号传递的跨膜蛋白,信号传导过程中与受体偶联的物质称为配体,对于不清楚内源性配体物质的G蛋白偶联受体称为孤儿G蛋白偶联受体。血管紧张素受体样受体是一种孤儿G蛋白偶联受体。其内源性配体Apelin新近从牛胃抽提液中被分离出来,现发现apelin的功能涉及心血管系统,中枢神经系统,免疫系统等。Apelin在血管紧张素Ⅰ转化酶的同源酶血管紧张素Ⅰ转化酶2的作用下有活性形式转变成无活性的形式。现对apelin在心血管系统以及以其它众多生物学功能研究进展作一综述。

GPR37在骨髓瘤细胞黏附介导的耐药中的作用及意义

目的:研究G蛋白耦联受体37(orphan G protein-coupled receptor 37,GPR37)在细胞黏附介导的多发性骨髓瘤细胞耐药过程中的表达变化及其生物学作用。方法:采用多发性骨髓瘤细胞株RPMI 8226与纤黏蛋白(fibronectin,FN)或骨髓基质细胞株HS-5共培养构建细胞黏附模型。Western Blot检测GPR37分别在悬浮和黏附状态的RPMI 8226细胞中的蛋白表达水平。钙黄绿素实验检测改变GPR37的表达对RPMI 8226细胞黏附的影响,并采用化疗药物多柔比星处理细胞,CCK-8试剂盒检测上述处理对RPMI 8226细胞活力的影响。结果:Western Blot结果显示GPR37在RPMI8226细胞黏附模型中低表达。钙黄绿素实验结果显示RPMI 8226细胞过表达GPR37后其黏附能力显著降低。CCK-8实验结果表明GPR37过表达能显著增强RPMI 8226细胞对化疗药物多柔比星的敏感性。结论:GPR37可能通过影响骨髓瘤细胞与基质细胞的黏附能力从而影响其对化疗药物的敏感性。