G蛋白偶联受体异源二聚化及其药理学意义

G蛋白偶联受体(G-protein coupled receptors, GPCRs)是细胞膜表面最大的跨膜蛋白超家族受体,在细胞的信号转导中发挥着重要的作用,是重要的药物靶标。目前越来越多的证据表明GPCRs的异源二聚化可以产生不同于单体的信号通路及功能,从而大大增加了有效的药物靶标数量,因此研究GPCRs的异源二聚化激活机制具有重要的药理学意义。本文就以上内容的最新研究进展进行综述,为相关科研人员研究GPCRs异源二聚化提供理论基础。     

G蛋白偶联受体与血栓的形成

G蛋白偶联受体(GPCRs)是具有七个跨膜结构域的受体,它通过与细胞内的G蛋白相互作用而发挥作用。血栓是由血小板在血管受伤后为控制血液流失从而发生活化、粘附、聚集形成的,在这个过程中,GPCRs发挥着重要的调节作用。本文就GPCRs通过不同的信号通路调节血栓形成而展开综述。     

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.     

靶向G蛋白偶联受体的肽类药物

G蛋白偶联受体(G protein-coupled receptors,GPCRs)是哺乳动物体内最大的细胞膜表面受体家族,具有7次跨膜螺旋结构.人类基因组编码约800种不同类型的GPCRs,广泛参与了代谢性疾病及肿瘤等多种重大疾病的病理过程,使之成为药物研发的热门靶点.肽是介于氨基酸和蛋白质之间的一类物质,由两个至几...     

G蛋白偶联受体失敏的分子机制

G蛋白偶联受体（GPCRs)受到激动剂持续刺激对易发生失敏。受体内化是GPCRs失敏重要分子机制。GPCRs在G蛋白产受体激酶（GRKs)、第二信使调节激酶等作用下发生磷酸化,磷酸化的GPCRs与抑制蛋白（arrestins)结合后导致受体与G蛋白失偶联,并通过胞吞由细胞膜表面向膜内转移,从而因GPCRs的内化而表现为失敏。     

G蛋白偶联受体相关分选蛋白功能特征与相关疾病研究进展

G蛋白偶联受体(G protein-coupled receptors, GPCRs)作为最大的一类膜蛋白受体家族,可被多种配体激活并发挥相应的信号转导功能,参与生物体内重要的生理过程。G蛋白偶联受体相关分选蛋白(G protein-coupled receptors associated sorting proteins, GASPs)则对内吞后的GPCRs分选过程发挥着重要的作用,并介导受体进入降解或再循环途径,进而调控细胞的信号转导等过程。研究发现GASPs的功能缺陷与多种疾病相关,包括神经系统疾病、肿瘤和耳聋等。本文重点介绍了G蛋白偶联受体相关分选蛋白的功能特征及其相关信号通路,描述了GASPs功能缺陷与疾病的关联性及家族蛋白与GPCRs的相互作用、GASPs分选途径的发现、参与的信号通路及对基因转录调控,以期为GASPs相关多种疾病的治疗提供新的思路和策略。     

β-arrestin的生物学研究进展

β-arrestin 1和2是一类介导受体脱敏的重要可溶性蛋白质,对绝大部分与受体偶联G蛋白介导的信号转导具有重要调节作用,在G蛋白偶联受体(G protein-coupled receptors, GPCRs)脱敏、内化、复敏、细胞增殖反应和基因转录中具有重要地位.对β-arrestin介导的复杂信号通路的研究将揭示它们的调节功能对人类健康的影响,有助于开发新一代影响GPCRs的药物.     

植物G蛋白偶联受体及其在信号转导中的作用

G蛋白偶联受体(G protein-coupled receptors,GPCRs)是具有7个跨膜螺旋的蛋白质受体,是人体内最大的蛋白质超家族.GPCRs能调控细胞周期,参与多种植物信号通路以及影响一系列的代谢和分化活动.简要介绍了GPCR和G蛋白介导的信号转导机制,GPCRs的结构和植物GPCR及其在植物跨膜信号转导中的作用,并对GPCR的信号转导机制及植物抗病反应分子机制的研究提出展望.     

与阿尔兹海默症相关的G 蛋白偶联受体研究进展

G蛋白偶联受体(GPCRs)在大脑信号传递中至关重要,而在阿尔兹海默症(AD)中,G蛋白偶联受体通过调控α-、β-及γ-分泌酶分泌、淀粉样前体蛋白(APP)生成及β-淀粉样蛋白(Aβ)降解,直接影响β-淀粉样蛋白在神经系统信号级联反应;另外,阿尔兹海默症中β-淀粉样蛋白的生成可以扰乱G蛋白偶联受体功能.因此,阐明G蛋白偶联受体与阿尔兹海默症发病之间的关联有助于开发以G蛋白偶联受体为靶点的阿尔兹海默症治疗药物.     

降钙素基因相关肽受体研究的新进展

降钙素基因相关肽(calcitonin gene-related peptide,CGRP)是一种神经肽,它由37个氨基酸残基组成。CGRP通过激活细胞膜上的CGRP受体参与循环系统、神经系统等功能的调节,特别是CGRP在血管舒张以及偏头痛中发挥着重要的作用。过去认为CGRP受体是一种经典的G蛋白偶联受体,具有G蛋白偶联受体的结构特性。近年来发现,与经典的G蛋白偶联受体不同,具有生物活性的CGRP受体由降钙素受体样受体(calcitonin receptor-like receptor,CLR)、受体活性修饰蛋白-1(receptor activity modifying protein,RAMP1)和受体组成蛋白(receptor component protein,RCP)组成,CGRP受体的这些不同组分在跨膜信号转导中分别发挥不同的作用。RAMP参与多种G蛋白偶联受体的组成,在G蛋白偶联受体的表型及功能调节等方面具有重要的作用。所以,RAMP的发现修正了有关G蛋白偶联受体的基本概念和理论。目前对CLR,RAMP以及RCP在CGRP受体激活和信号转导中作用的研究已经有了很大的进展。深入研究RAMP的胞外N末端和RAMP的单跨膜区域如何协同CLR以识别并结合相应的配体,以及G蛋白与RCP之间怎样相互作用,都将为有关G蛋白偶联受体的理论提供新的内容。本文将综述CGRP受体各组分的结构和功能,以及它们之间的相互作用对CGRP受体功能的影响。     

Structural biology of G protein‐coupled receptor signaling complexes

G protein‐coupled receptors (GPCRs) constitute the largest family of cell surface receptors that mediate numerous cell signaling pathways, and are targets of more than one‐third of clinical drugs. Thanks to the advancement of novel structural biology technologies, high‐resolution structures of GPCRs in complex with their signaling transducers, including G‐protein and arrestin, have been determined. These 3D complex structures have significantly improved our understanding of the molecular mechanism of GPCR signaling and provided a structural basis for signaling‐biased drug discovery targeting GPCRs. Here we summarize structural studies of GPCR signaling complexes with G protein and arrestin using rhodopsin as a model system, and highlight the key features of GPCR conformational states in biased signaling including the sequence motifs of receptor TM6 that determine selective coupling of G proteins, and the phosphorylation codes of GPCRs for arrestin recruitment. We envision the future of GPCR structural biology not only to solve more high‐resolution complex structures but also to show stepwise GPCR signaling complex assembly and disassembly and dynamic process of GPCR signal transduction.     

G protein mediated signaling pathways in lysophospholipid induced cell proliferation and survival

Agonist activation of a subset of G protein coupled receptors (GPCRs) stimulates cell proliferation, mimicking the better known effects of tyrosine kinase growth factors. Cell survival or apoptosis is also regulated via pathways initiated by stimulation of these same GPCRs. This review focuses on aspects of signaling by the lysophospholipid mediators, lysophosphatidic acid (LPA), and sphingosine 1 phosphate (S1P), which make these agonists uniquely capable of modulating cell growth and survival. The general features of GPCR coupling to specific G proteins, downstream effectors and signaling cascades are first reviewed. GPCR coupling to G(i) and Ras/MAPK or to G(q) and phospholipase generated second messengers are insufficient to regulate cell proliferation while G(12/13)/Rho engagement provides additional complementary signals required for cell proliferation. Survival is best predicted by coupling to G(i) pathways that regulate PI3K and Akt, but other signals generated through different G protein pathways are also implicated. The unique ability of LPA and S1P to concomitantly stimulate G(i), G(q), and G(12/13) pathways, given the proper complement of expressed LPA or S1P receptors, allows these receptors to support cell survival and proliferation. In pathophysiological situations, e.g., vascular disease, cancer, brain injury, and inflammation, components of the signaling cascade downstream of lysophospholipid receptors, in particular those involving Ras or Rho, may be altered. In addition, up or downregulation of LPA or S1P receptor subtypes, altering their ratio, and increased availability of the lysophospholipid ligands at sites of injury or inflammation, likely contribute to disease and may be important targets for therapeutic intervention.     

Insights into cellular signalling by G protein coupled receptor transactivation of cell surface protein kinase receptors

G protein coupled receptor (GPCR) signalling is mediated by transactivation independent and transactivation dependent pathways. GPCRs transactivate protein tyrosine kinase receptors (PTKRs) and protein serine/threonine kinase receptors (PS/TKR). Since the initial observations of transactivation dependent signalling, there has been an effort to understand the mechanisms behind this phenomena. GPCR signalling has evolved to include biased signalling. Biased signalling, whereby selected ligands can activate the same GPCR that can generate multiple signals, but drive only a unique response. To date, there has been no focus on the ability of biased agonists to activate the PTKR and PS/TKR transactivation pathways differentially. As such, this represents a novel direction for future research. This review will discuss the main mechanisms of GPCR mediated receptor transactivation and the pathways involved in intracellular responses.     

Structural Features of β2 Adrenergic Receptor: Crystal Structures and Beyond

The beta2-adrenergic receptor (β2AR) family, which is the largest family of cell surface receptors in humans. Extra attention has been focused on the human GPCRs because they have been studied as important protein targets for pharmaceutical drug development. In fact, approximately 40% of marketed drugs directly work on GPCRs. GPCRs respond to various extracellular stimuli, such as sensory signals, neurotransmitters, chemokines, and hormones, to induce structural changes at the cytoplasmic surface, activating downstream signaling pathways, primarily through interactions with heterotrimeric G proteins or through G-protein independent pathways, such as arrestin. Most GPCRs, except for rhodhopsin, which contains covalently linked 11 cis-retinal, bind to diffusible ligands, having various conformational states between inactive and active structures. The first human GPCR structure was determined using an inverse agonist bound β2AR in 2007 and since then, more than 20 distinct GPCR structures have been solved. However, most GPCR structures were solved as inactive forms, and an agonist bound fully active structure is still hard to obtain. In a structural point of view, β2AR is relatively well studied since its fully active structure as a complex with G protein as well as several inactive structures are available. The structural comparison of inactive and active states gives an important clue in understanding the activation mechanism of β2AR. In this review, structural features of inactive and active states of β2AR, the interaction of β2AR with heterotrimeric G protein, and the comparison with β1AR will be discussed.     

Thematic Minireview Series: New Directions in G Protein-coupled Receptor Pharmacology

Over the past half-century, The Journal of Biological Chemistry has been the venue for many landmark publications on the topic of G protein-coupled receptors (GPCRs, also known as seven-transmembrane receptors). The GPCR superfamily in humans is composed of about 800 members, and is the target of about one-third of all pharmaceuticals. Most of these drugs target a very small subset of GPCRs, and do so by mimicking or competing with endogenous hormones and neurotransmitters. This thematic minireview series examines some emerging trends in GPCR drug discovery. The first article describes efforts to systematically interrogate the human “GPCR-ome,” including more than 150 uncharacterized “orphan” receptors. The second article describes recent efforts to target alternative receptor binding sites with drugs that act as allosteric modulators of orthosteric ligands. The third article describes how the recent expansion of GPCR structures is providing new opportunities for computer-guided drug discovery. Collectively, these three articles provide a roadmap for the most important emerging trends in GPCR pharmacology.     

When a G protein-coupled receptor does not couple to a G protein

Classically, G protein-coupled receptors (GPCRs) relay signals by directly activating heterotrimeric guanine nucleotide-binding proteins (G proteins). Increasing evidence indicates that GPCRs may also signal through G protein-independent pathways. JAK/STATs, Src-family tyrosine kinases, GRKs/beta-arrestins, and PDZ domain-containing proteins have been suggested to directly relay signals from GPCRs independent of G proteins. In addition, our laboratory recently reported that the beta(2) adrenergic receptor (beta(2)AR) could switch from G protein-coupled to G protein-independent ERK (extracellular signal-regulated kinase) activation in an agonist dosage-dependent manner. This finding provides a novel mechanism for G protein-independent GPCR signaling. This review focuses on recent progress in understanding the mechanisms by which G protein-independent GPCR signaling occurs.     

Increasingly accurate dynamic molecular models of G-protein coupled receptor oligomers: Panacea or Pandora's box for novel drug discovery?

For years, conventional drug design at G-protein coupled receptors (GPCRs) has mainly focused on the inhibition of a single receptor at a usually well-defined ligand-binding site. The recent discovery of more and more physiologically relevant GPCR dimers/oligomers suggests that selectively targeting these complexes or designing small molecules that inhibit receptor–receptor interactions might provide new opportunities for novel drug discovery. To uncover the fundamental mechanisms and dynamics governing GPCR dimerization/oligomerization, it is crucial to understand the dynamic process of receptor–receptor association, and to identify regions that are suitable for selective drug binding. This minireview highlights current progress in the development of increasingly accurate dynamic molecular models of GPCR oligomers based on structural, biochemical, and biophysical information that has recently appeared in the literature. In view of this new information, there has never been a more exciting time for computational research into GPCRs than at present. Information-driven modern molecular models of GPCR complexes are expected to efficiently guide the rational design of GPCR oligomer-specific drugs, possibly allowing researchers to reach for the high-hanging fruits in GPCR drug discovery, i.e. more potent and selective drugs for efficient therapeutic interventions.     

Trends in application of advancing computational approaches in GPCR ligand discovery

G protein-coupled receptors (GPCRs) comprise the most important superfamily of protein targets in current ligand discovery and drug development. GPCRs are integral membrane proteins that play key roles in various cellular signaling processes. Therefore, GPCR signaling pathways are closely associated with numerous diseases, including cancer and several neurological, immunological, and hematological disorders. Computer-aided drug design (CADD) can expedite the process of GPCR drug discovery and potentially reduce the actual cost of research and development. Increasing knowledge of biological structures, as well as improvements on computer power and algorithms, have led to unprecedented use of CADD for the discovery of novel GPCR modulators. Similarly, machine learning approaches are now widely applied in various fields of drug target research. This review briefly summarizes the application of rising CADD methodologies, as well as novel machine learning techniques, in GPCR structural studies and bioligand discovery in the past few years. Recent novel computational strategies and feasible workflows are updated, and representative cases addressing challenging issues on olfactory receptors, biased agonism, and drug-induced cardiotoxic effects are highlighted to provide insights into future GPCR drug discovery.     

Multiplex GPCR assay in reverse transfection cell microarrays

G protein-coupled receptors (GPCRs) are a superfamily of proteins that include some of the most important drug targets in the pharmaceutical industry. Despite the success of this group of drugs, there remains a need to identify GPCR-targeted drugs with greater selectivity, to develop screening assays for validated targets, and to identify ligands for orphan receptors. To address these challenges, the authors have created a multiplexed GPCR assay that measures greater than 3000 receptor: ligand interactions in a single microplate. The multiplexed assay is generated by combining reverse transfection in a 96-well plate format with a calcium flux readout. This assay quantitatively measures receptor activation and inhibition and permits the determination of compound potency and selectivity for entire families of GPCRs in parallel. To expand the number of GPCR targets that may be screened in this system, receptors are cotransfected with plasmids encoding a promiscuous G protein, permitting the analysis of receptors that do not normally mobilize intracellular calcium upon activation. The authors demonstrate the utility of reverse transfection cell microarrays to GPCR-targeted drug discovery with examples of ligand selectivity screening against a panel of GPCRs as well as dose-dependent titrations of selected agonists and antagonists.