GABAB 受体变构剂药学研究进展

Y-氨基丁酸B受体(GABAB receptor,GABABR)是最具有药理学意义的药物靶点之一,具有复杂而精细的激活机制.传统的GABABR靶点药物开发集中于激动剂和拮抗剂,这类药物受到多种因素的制约,包括较强的副作用、药物代谢困难、机体耐药性明显等.变构剂结合于正构位点之外,能够调节GABABR异源二聚体亚基或结构域间的相互作用.正向变构剂(positive allosteric modulators,PAMs)和负向变构剂(negative allosteric modulators,NAMs)分别可以提高或降低GABABR的活性,并具有较高的特异性和药物安全性,同时还能够保持GABABR信号在时间和空间上的可控性.变构剂为GABABR靶点药物开发提供了新思路.     

GABAB受体变构剂药学研究进展

Y-氨基丁酸B受体(GABAB receptor,GABABR)是最具有药理学意义的药物靶点之一,具有复杂而精细的激活机制.传统的GABABR靶点药物开发集中于激动剂和拮抗剂,这类药物受到多种因素的制约,包括较强的副作用、药物代谢困难、机体耐药性明显等.变构剂结合于正构位点之外,能够调节GABABR异源二聚体亚基或结构域间的相互作用.正向变构剂(positive allosteric modulators,PAMs)和负向变构剂(negative allosteric modulators,NAMs)分别可以提高或降低GABABR的活性,并具有较高的特异性和药物安全性,同时还能够保持GABABR信号在时间和空间上的可控性.变构剂为GABABR靶点药物开发提供了新思路.     

GABAB受体活性调控机制的研究进展

γ-氨基丁酸B型受体(GABAB receptor,GABABR)是由GABAB1(GB1)和GABAB2(GB2)亚基组成的异源二聚体,在中枢神经系统中介导持久而缓慢的神经抑制活动。GABAB受体活性受多种因素的调控,如受体的胞内运输、受体的内吞和再循环、受体与胞内蛋白相互作用等,在神经元维持突触可塑性、产生快速神经抑制信号等方面起着非常重要的作用,其活性失调则导致自发性癫痫、痉挛药物成瘾、精神分裂症等多种严重疾病。     

非洲爪蟾卵母细胞GABA_B和GABA_C受体介导的电流反应

实验应用双电极电压箝技术 ,在具有滤泡膜的非洲爪蟾 (Xenopuslaevis)卵母细胞上记录到γ 氨基丁酸(γ aminobutyricacid ,GABA) 激活电流。此GABA 激活电流的特点及有关GABA受体类型的研究和分析如下 :( 1)在 3 5 5 % ( 5 5 / 15 5 )的受检细胞外加GABA可引起一慢的浓度依赖性的外向电流。 ( 2 )GABAA 受体的选择性拮抗剂bicuculline ( 10 -5mol/L)对GABA ( 10 -5mol/L)引起的外向电流无阻断作用 (n =6)。 ( 3 )GABAB 受体的选择性拮抗剂2 hydroxysaclofen ( 10 -4mol/L)能将GABA ( 10 -5mol/L)引起的外向电流可逆性地转变为内向电流 ,后者又可被GABAC 受体的选择性拮抗剂I4AA ( 10 -5mol/L)所消除 (n =6)。 ( 4 )GABAB 受体的特异性激动剂baclofen可引起部分 ( 2 0 % ,12 / 60 )受检细胞产生一慢的浓度依赖性的外向电流。 3× 10 -6 、3× 10 -5及 3× 10 -4mol/L 2 hydroxysaclofen分别阻断baclofen ( 10 -5mol/L) 激活电流 ( 6 3± 3 2 ) % ,( 4 4 1± 2 2 ) %及 ( 86 0± 1 6) % (n =6)。 ( 5 )baclofen激活电流的I V曲线显示逆转电位在 - 96 8± 7 2mV左右 ,此电流可分别被TEA ( 5mmol/L)和BaCl2 ( 2mmol/L)所阻断。以上结果提示 :在非洲爪蟾的卵母细胞上存在内源性GABAB 和GABAC 受体 ,GA     

基于受体的药物高通量筛选研究进展

受体是药物筛选的重要靶标,基于受体的药物高通量筛选是药物筛选的主要类型之一。本文根据受体作用原理,按照检测对象的不同,从直接与间接检测的角度,将基于受体的药物高通量筛选进行了分类,总结了基于受体的几种不同的药物筛选模型,并简要介绍了高通量筛选技术在中药研究中的应用,对药物筛选的发展进行了展望。     

变构菌素生物合成基因簇的研究进展

变构菌素是从Streptomyces griseochromogenes菌株中分离得到的第一个高选择性的蛋白磷酸化酶-1（PP-1）抑制剂。变构菌素及其衍生物在神经系统紊乱、代谢综合症、呼吸系统及相关疾病、免疫抑制、肿瘤治疗等诸多领域都有着广泛的应用前景,因而引起了人们对其生物合成途径的研究兴趣。介绍了近年来变构菌素生物合成途径的研究进展。     

抑菌剂和筛选剂对香蕉受体系统的影响

本研究将抑制农杆菌生长的两种抑菌剂头孢霉素和特泯丁,以及3种筛选剂潮霉素B、卡那霉素和PPT除草剂,以不同浓度添加到香蕉的3种受体系统中,研究它们对香蕉组织生长与分化的影响.实验结果表明:不同抑菌剂和筛选剂对香蕉再生体系的影响程度不同,不同香蕉再生体系对相同抑菌剂和筛选剂的敏感性也不同,因此不同香蕉再生体系需要选择不同的抑菌剂与筛选剂的最佳的配比和组合配比.3种筛选剂在香焦的3种再生体系中的筛选能力顺序都为:PPT＞潮霉素B＞卡那霉素.     

P2X受体调节剂的作用机制与最新研究进展

ATP激活的配体门控阳离子通道P2X受体参与多种生理病理功能,是一类重要的新药靶标。目前发现的多种靶向P2X受体的小分子药物多数因结果未达到预期或存在明显的副作用而止步于临床研究。明确的调节机制可为靶向P2X受体的理性药物设计提供新的方向,从而提高药物发现概率和有效性。本文就P2X受体调节剂的作用机制进行综述,并对靶向P2X受体的小分子药物最新研究进展进行总结。     

超螺旋DNA的碱变构研究

对超螺旋ＤＮＡ（ＤＮＡⅠ）的碱处理产物进行了琼脂糖凝胶电泳,氯化铯－溴化乙锭密度梯度超离心分析,紫外吸收光谱分析和电镜观察。实验结果表明超螺旋ＤＮＡ在碱性环境中的结构改变发生在很窄的ｐＨ范围内（ｐＨ１２．８８─１３．００）．超过ｐＨ临界点的超螺旋ＤＮＡ碱变构产物紫外吸收高于同浓度天然ＤＮＡ紫外吸收的２９％。变构产物在ＣｓＣｌ－ＥＢ密度梯度超离心中的高密度区形成稳定的区带．用透射电镜的观察表明碱变构的超螺旋ｐＢＲ３２２ＤＮＡ具有高电子密度并呈中空颗粒状,以上事实表明,ＤＮＡ在高ｐＨ下可产生一种结构有序的相对稳定的产物．这些结果意味着在碱处理过程中,超螺旋ＤＮＡ在构象上发生了改变,使其分子由扭曲线形变成球形颗粒状。根据实验事实本文对超螺旋ＤＮＡ的碱变构产物（ＤＮＡⅣ）提出一个新的结构模型──压缩模型。这个模型能更合理地解释一些实验现象。     

乙型肝炎病毒核心蛋白变构调节剂的研究进展

由于乙型肝炎病毒(hepatitis B virus,HBV)的共价闭合环状DNA的持续存在和病毒介导的宿主免疫反应钝化,导致慢性乙型肝炎病毒感染很难治愈。现有的核苷(酸)类似物或聚乙二醇干扰素疗法难以实现高比率的HBV表面抗原清除。目前正在研发的核心蛋白变构调节剂有望大幅度降低血清表面抗原。本文就HBV核心蛋白的结构、功能以及核心蛋白变构调节剂的分类、应用前景等方面进行综述。     

Allosteric Agonist Modulators

This article discusses a model to describe the effects of molecules that bind to a site on the receptor separate from that of the endogenous agonist to actively produce receptor signals (direct agonism). In addition, these molecules also modify the biological responses of the endogenous agonist (either potentiation or antagonism). The effects of such compounds in high-throughput screening assays are described as well as their effects on the dose-response curves to conventional agonists.     

Integrative Action of Receptor Mosaics: Relevance of Receptor Topology and Allosteric Modulators

After a definition of the receptor mosaic (RM, high order heteromer or homomer) concept, this study analyzes some relevant theoretical aspects related to receptor-receptor interactions (RRIs). In particular, the possible influence of the plasma membrane microdomain on RM integrative functions are discussed. Furthermore, a possible mathematical approach may identify the RM topologies [i.e., the spatial arrangements the receptors (tesserae of the mosaic) can assume within the RM assembly]. Finally, data are presented on homocysteine possible biasing action on the well-characterized heterodimer/receptor mosaic formed by adenosine A2A and dopamine D2 receptors. We discuss how these findings can lead to a new possible approach for developing drugs for the treatment of certain neuropsychiatric disorders.     

Novel Allosteric Modulators of G Protein-coupled Receptors

G protein-coupled receptors (GPCRs) are allosteric proteins, because their signal transduction relies on interactions between topographically distinct, yet conformationally linked, domains. Much of the focus on GPCR allostery in the new millennium, however, has been on modes of targeting GPCR allosteric sites with chemical probes due to the potential for novel therapeutics. It is now apparent that some GPCRs possess more than one targetable allosteric site, in addition to a growing list of putative endogenous modulators. Advances in structural biology are also shedding new insights into mechanisms of allostery, although the complexities of candidate allosteric drugs necessitate rigorous biological characterization.     

Allosteric modulation of adenosine receptors

Allosteric modulators for adenosine receptors may have potential therapeutic advantage over orthosteric ligands. Allosteric enhancers at the adenosine A₁ receptor have been linked to antiarrhythmic and antilipolytic activity. They may also have therapeutic potential as analgesics and neuroprotective agents. A₃ allosteric enhancers are postulated to be useful against ischemic conditions or as antitumor agents. In this review, we address recent developments regarding the medicinal chemistry of such compounds. Most efforts have been and are directed toward adenosine A₁ and A₃ receptors, whereas limited or no information is available for A_2A and A_2B receptors. We also discuss some findings, mostly receptor mutation studies, regarding localization of the allosteric binding sites on the receptors.     

Allosteric Modulation of Flunitrazepam Binding to Rat Brain Benzodiazepine Receptors by Methyl β-Carboline-3-Carboxylate

The inhibition of flunitrazepam (FNP) binding to rat brain benzodiazepine (BZ) receptors by methyl beta-carboline-3-carboxylate (MCC) was studied. Biphasic dissociation was observed for [3H]FNP and [3H]MCC in cerebral cortex, cerebellum, and hippocampus, although the dissociation of [3H]MCC was much faster. The dissociation rate of [3H]FNP was increased by MCC in the cerebellum, but was not altered in cerebral cortex or hippocampus. [3H]FNP binding stimulated by gamma-aminobutyric acid was enhanced in the presence of MCC in all three regions examined. These results indicate that MCC exerts these effects by interacting with allosteric sites that are different from the FNP recognition sites on the BZ receptors.     

Benzodiazepine ligands can act as allosteric modulators of the Type 1 cholecystokinin receptor

The cholecystokinin (CCK₁) receptor is a G protein-coupled receptor important for nutrient homeostasis. The molecular basis of CCK-receptor binding has been debated, with one prominent model suggesting occupation of the same region of the intramembranous helical bundle as benzodiazepines. Here, we used a specific assay of allosteric ligand interaction to probe the mode of binding of devazepide, a prototypic benzodiazepine ligand. Devazepide elicited marked slowing of dissociation of pre-bound CCK, only possible through binding to a topographically distinct allosteric site. This effect was disrupted by chemical modification of a cysteine in the benzodiazepine-binding pocket. Application of an allosteric model to the equilibrium interaction between a series of benzodiazepine ligands and CCK yielded quantitative estimates of each modulator’s affinity for the allosteric site, as well as the degree of negative cooperativity for the interaction between occupied orthosteric and allosteric sites. The allosteric nature of benzodiazepine binding to the CCK₁ receptor provides new opportunities for small molecule drug development.     

Protection by Alcuronium of Muscarinic Receptors Against Chemical Inactivation and Location of the Allosteric Binding Site for Alcuronium

Abstract: We have found earlier that the neuromuscular blocker alcuronium binds to cardiac muscarinic receptors simultaneously with their specific antagonist [³H]methyl- N -scopolamine ([³H]NMS) and allosterically increases their affinity to this ligand. Nothing is known about the allosteric site with which alcuronium interacts. To gain an insight, we have now investigated how the binding of [³H]NMS is affected by agents known to modify specific residues in proteins and how their effects are altered by alcuronium. Reagents that covalently modify the tyrosyl residues ( p -nitrobenzenesulfonyl fluoride and 4-chloro-7-nitrobenzofurazan) and the carboxyl groups of aspartate and glutamate [1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, N,N' -dicyclohexylcarbodiimide, and N -ethyl-5-phenylisoxazolium-3'-sulfonate] blocked the binding of [³H]NMS to receptors in rat heart atria. Their action was probably due to the modification of tyrosyl and aspartyl residues directly in the muscarinic binding sites because it was antagonized by atropine and carbamoylcholine. Alcuronium and gallamine, another allosteric ligand, also protected the [³H]NMS binding sites against the inactivation by tyrosine- and carboxyl-directed chemical modifiers just as well as by benzilylcholine mustard, known to attach covalently to the muscarinic binding sites. Protection by alcuronium has also been observed on cerebrocortical muscarinic receptors. The effect of alcuronium indicates that the drug interferes with the access of chemical modifiers to the muscarinic sites. In view of the unspecific nature of most of the modifiers used (with regard to muscarinic mechanisms), the protection by alcuronium appears to be best explained on the assumption that the drug binds in close vicinity of the "classical" muscarinic site and sterically blocks the access to this site.     

Pretreatment of Rat Brain Synaptosomes with GABA Increases Subsequent GABA Uptake Via GABAB Receptor Activation

Pretreatment with 100 M GABA of synaptosomes purified from rat brain results in an increased uptake of the labelled neurotransmitter in subsequent incubations. The effect is blocked by a GABA_B receptor antagonist, 2-hydroxy-saclofen. The effect is mimicked by baclofen and the baclofen effect is blocked by saclofen too. Lower GABA concentrations (up to 50 M) do not result in an increase of subsequent GABA uptake. Treatment of synaptosomes with 8-Br-cAMP results in a decreased GABA uptake. Since the uptake incubations were run with saturating concentrations of labelled GABA, the data indicates that GABA_B receptor activation in brain synaptosomes up-regulates their GABA uptake capacity by an increase in V_max. This mechanism appears of physiological relevance under conditions of sustained GABA release and substantial increase of its extracellular concentration.