重症肌无力患者抗乙酰胆碱受体抗体的测定及意义

用ELISA法对56例重症肌无力(MG)患者治疗前后的血清乙酰胆碱受体(AchR)抗体进行了检测。检测结果为MG患者治疗前后的血清AchR抗体阳性率46.4%。而且发病年龄越大,患者体内AchR抗体阳性率越高。患者患病时间越长体内AchR抗体含量降低。伴发胸腺瘤的患者AchR抗体阳性率明显高于胸腺正常者,全身型MG患者AchR抗体检测阳性率高于眼肌型患者。     

全反式维甲酸对乙酰胆碱受体特异性淋巴细胞的免疫调控作用

目的:观察全反式维甲酸(ATRA)对乙酰胆碱受体(AChR)特异性淋巴细胞的体外调控作用,探讨其治疗重症肌无力(MG)的可能机制。方法:建立完全弗氏佐剂(CFA)对照组及实验性自身免疫性重症肌无力(EAMG)组大鼠,并获取淋巴结单个细胞悬液,以ACh R97-116多肽片段以及不同浓度的ATRA体外培养72 h,采用流式细胞仪法、CCK-8法、ELISA法分别检测活细胞比例、细胞凋亡和周期的改变以及Th亚群的格局和B细胞抗体分泌能力的变化。结果:ATRA显著降低活细胞比例(P0.001);不同浓度的ATRA均促进了特异性细胞群的凋亡(P0.001),且呈剂量依赖性,而ATRA未改变AChR特异性淋巴细胞的生长周期;ATRA处理后,CFA和EAMG组的淋巴细胞增殖均受到明显抑制,且ATRA对ACh R特异性的淋巴细胞的抑制明显(EAMG组,P0.01)于CFA组(P0.05);ATRA干预后,ACh R特异性CD4+T淋巴细胞的比例下降(P0.01),且ATRA促进了Th2、Treg细胞亚群百分比(P_(IL-4)0.001,P_(Foxp3)0.001),而抑制了促炎性的Th17、Th1细胞亚群百分比(P_(IL-17)0.05,P_(IFN-γ)0.001);ATRA能够降低ACh R特异性B细胞的抗体分泌能力(P0.01)。结论:ATRA不仅能抑制ACh R特异性T细胞功能,同时也能抑制ACh R特异性B细胞功能,其在MG的临床治疗中可能起治疗作用。     

一株乙酰胆碱受体单克隆抗体的序列分析

探讨重症肌无力自身抗体分子结构及其在发病机制中的作用。利用PCR从分泌乙酰胆碱受体（AChR）单抗A49的杂交瘤细胞株扩增抗体可变区（V）基因,经转化大肠杆菌DH5α克隆后,进行核苷酸序列分析。A49的重性V区基因由小鼠VHNP族基因编码,轻链V区基因由小鼠VK2组基因编码。与致病性AChR抗体V区比较,其同源性均在70％以下。A49的分子结构与致病性AChR抗体不同。     

乙酰胆碱受体结构与功能的研究进展

乙酰胆碱受体是一种神经递质介导的离子通道受体 ,由 5个同源亚基组成。乙酰胆碱受体包括肌肉型和神经型两种。肌肉型乙酰胆碱受体是肌肉神经传导中的重要媒介物质以及自身免疫疾病重症肌无力的主要免疫原 ,神经型乙酰胆碱受体的突变也可导致某些疾病的发生。扼要介绍了近年来乙酰胆碱受体结构与功能的研究进展。     

IRF5调控AChR特异性T细胞参与EAMG疾病发生、发展的实验研究

目的:体内外实验探讨干扰素调节因子5(Interferon regulatory factor 5,IRF5)在乙酰胆碱受体(Acetylcholine Receptor,ACh R)特异性T、B细胞中的表达情况以及与实验性自身免疫性重症肌无力(Experimental Autoimmune Myasthenia Gravis,EAMG)疾病的发生存在的可能关系。方法:ELISA法检测不同发病时相大鼠血清中IRF5的含量;流式细胞仪法检测早期晚期发病时相CD4+T细胞以及CD45R+B细胞中IRF5的表达情况;QPCR法及Western blotting法分别检测体外ACh R刺激不同时间点的T、B细胞中IRF5的m RNA和蛋白水平的表达差异。结果:血清学检测结果显示,IRF5高表达于EAMG大鼠的晚期发病时相的血清中,并随着疾病进程的不断加重呈现逐渐增高的表达,与CFA对照组大鼠相比较差异显著,有统计学意义(***,P0.001);流式结果表明,来自EAMG大鼠早、晚期发病时相的无论是淋巴结还是脾脏中的ACh R特异性T细胞均高表达IRF5,且与CFA对照组相比较,有统计学差异,而B细胞中IRF5的表达即便是在晚期发病时相也与CFA对照组无明显区别;QPCR结果发现,EAMG晚期发病时相的ACh R特异性T细胞在经过ACh R体外刺激0 h,72 h后,均可见IRF5 m RNA水平的高表达,而B细胞中IRF5的m RNA水平则在两组中无统计学差异;Western blotting结果进一步证实,IRF5蛋白水平在ACh R特异性T细胞中呈现高表达。结论:IRF5是通过对ACh R特异性T淋巴细胞的调控进而参与EAMG疾病的发生和发展过程的。     

突触后细胞骨架与乙酰胆碱受体簇

乙酰胆碱受体(AChR)簇的形成在神经肌接头的生长过程中是非常关键的一步。突触后细胞骨架参与AChR簇的形成。     

干扰素通路调控与自身免疫疾病

干扰素信号通路是细胞抵抗病原微生物侵染的重要防线。通过识别病源相关模式分子、激活下游通路,干扰素的表达被显著上调并分泌于细胞外,作用于自身和周围细胞,引发众多下游基因的转录激活。这些基因产物直接参与抗侵染过程或调控机体免疫反应。干扰素信号通路需要被正确调控,其异常激活会导致炎症和自身免疫疾病的发生。正确地识别“自己”和“非己”分子是首要的一步。鉴于干扰素通路所抵抗的微生物侵染中,核酸分子是重要的免疫原性分子,内源性核酸分子的代谢调控显得尤为重要。细胞编码一系列参与核酸代谢的酶,这些蛋白质功能的发挥对保持细胞核酸稳态至关重要。以单基因突变引发的自身免疫疾病Aicardi-Goutières综合征为例,目前发现9种基因可突变致病,均来自DNA代谢相关的和RNA代谢相关的基因。尽管这9种基因突变都导致干扰素通路的异常激活,但中间所依赖的参与蛋白并不相同。可见,同样症状的疾病,其致病机理也可能不同,这也将影响有效治疗方案的确定,凸显基因检测在诊治自身免疫疾病中的必要性。本综述通过阐述细胞内环境稳态对干扰素通路正确识别“自己”和“非己”的重要作用,帮助理解自身免疫疾病的发病机理。     

消除疼痛的最终理想还有多远——一种离子通道病显示出疼痛的根源

医学的分类一向是以器官为基础,例如心脏病、胃病、甲状腺病。到了分子医学时代,常常以某一种分子或基因的异常作为疾病分类的基础,例如受体病（以乙酰胆碱受体自体免疫引起重症肌无力症、自身免疫性甲状腺病为例）、离子通道病（以钠离子通道突变引起伴有高热惊厥的癫痫、高钾性阵发性瘫痪为例）等等。这种分类有可能导致医学变革的新局面,目前仅仅是拉开了序幕。本文将介绍的是发生在中国的科学故事：一种皮肤病的研究,如何开启了寻找理想镇痛药的大门。     

烟碱型乙酰胆碱受体及其神经保护作用

新近研究证实,神经元烟碱型乙酰胆碱受体(nAChR)激动后可起到一定的神经保护作用.目前,一些作用于烟碱受体的激动剂已被作为治疗神经退行性疾病如阿尔茨海默病(AD)和帕金森病(PD)的候选药物,但是关于烟碱受体激动后如何发挥神经保护作用及其潜在的分子机制还不清楚,其中有与Ca2+相关的信号转导假说以及神经营养因子等假说.本文就烟碱型乙酰胆碱受体及其神经保护作用的研究进展予以综述.     

Constitutive Activity of Muscarinic Acetylcholine Receptors

We review the literature describing constitutive activity of the five muscarinic acetylcholine receptors in native and recombinant systems and discuss the effect of constitutive activity on muscarinic pharmacology in the context of modern models of receptor activation. We include a summary of mutations found to cause constitutive activity and discuss the implications of these data for the structure, function, and activation mechanism of muscarinic receptors. Finally, we discuss the possible physiological significance of constitutive activity of muscarinic receptors, incorporating information provided by targeted deletion of each of the muscarinic subtypes.     

Solubilization and Sedimentation Analysis of Muscarinic Acetylcholine Receptors

Abstract

To investigate if G-protein-receptor interactions can be characterized using sucrose density gradients (SDG) we have determined the experimental conditions for muscarinic acetylcholine receptor (mAChR) solubilization and analysis on SDG. Solubilization of 65–80% of [³H]QNB bound mAChR was accomplished with 1% of detergent. Analysis of solubilized receptors on SDG containing 0.4M KCl and 0.1% detergent demonstrated that the physical properties of the receptor-detergent complexes are influenced by the solubilizing detergent as well as detergents included in the SDG. Neither GTPγS nor NaF and AlCl₃ altered the sedimentation properties of mAChR, suggesting that the solubilized mAChR is no longer associated with G-protein under these conditions. Receptors bound to [³H]oxotremorine and [³H]QNB had similar sedimentation properties, suggesting that, once solubilized, mAChRs do not remain associated with G-proteins. Covalent labeling with [³H]PrBCM followed by solubilization and analysis on SDS-gel electrophoresis demonstrated the presence of intact receptor molecule. These observations suggest that the changes in the sedimentation properties of detergent-receptor complexes are independent of G-protein interactions and are influenced by the nature of the detergent associated with the mAChR during analysis.     

Solubilisation and Molecular Characterisation of Muscarinic Acetylcholine Receptors

Abstract

Stable, soluble preparations of rat brain muscarinic receptors can be prepared by extracting membranes with digitonin, or with combinations of sodium cholate and sodium chloride. The stability of the cholate/NaCl extract is enhanced by the addition of egg phosphatidylcholine, which, at the same time, suppresses the considerable dispersity apparent in the hydrodynamic behaviour of the solubilised receptor. The Stokes radius of the brain muscarinic receptor in cholate/NaCl/lecithin extracts is 6.7 nm, with very similar values in other detergents, including digitonin and sodium dodecyl sulphate. Its sedimentation coefficient is 3.78s, and its molecular weight approximately 110,000 after correction for detergent binding. The isoelectric point of the digitonin - solubilised receptor is approximately 4.5.     

Allosteric Drugs Acting at Muscarinic Acetylcholine Receptors

The binding properties of muscarinic acetylcholine receptors are affected by various drugs acting at a second (allosteric) binding site, usually (but not always) at supratherapeutic concentrations. Allosteric drugs acting at GABA receptors present advantages over competitive drugs; this explains the interest raised by allosteric effects on muscarinic receptors. A theoretical and practicable definition of allosteric drugs acting at muscarinic receptors will be given in this work, together with a summary of recent data concerning the number, position, and structural requirements of their binding sites.     

The Nicotinic Acetylcholine Receptor: Structure and Autoimmune Pathology

Abstract

The nicotinic acetylcholine receptors (AChR) are presently the best-characterized neurotransmitter receptors. They are pentamers of homologous or identical subunits, symmetrically arranged to form a transmembrane cation channel. The AChR subunits form a family of homologous proteins, derived from a common ancestor. An autoimmune response to muscle AChR causes the disease myasthenia gravis. This review summarizes recent developments in the understanding of the AChR structure and its molecular recognition by the immune system in myasthenia.     

毒蕈碱样乙酰胆碱受体及其信号转导

毒蕈碱样乙酰胆碱受体（MAChRs）是G蛋白偶联受体（GPCRs）超家族中的一员,具有该家族特性的结构和信号转导方式。GTP结合蛋白（Gproteins）是一类具有GTP酶活性的蛋白质,由α、β、γ三个亚基构成。其中α亚基结合GDP或GTP,分别代表G蛋白的非活化和活化状态。M受体与Gi/Go或Gq／11间的作用机制仍在探讨中,但基本过程与Gs介导的信号转导模式相似。激动剂持续作用后,G蛋白偶联受体激酶和阻滞蛋白导受体脱敏和内吞。     

Temperature-Sensitive Expression of Drosophila Neuronal Nicotinic Acetylcholine Receptors

Abstract: Heterologous expression of cloned Drosophila nicotinic acetylcholine receptor (nAChR) subunits indicates that these proteins misfold when expressed in mammalian cell lines at 37°C. This misfolding can, however, be overcome either by growing transfected mammalian cells at lower temperatures or by the expression of Drosophila nAChR subunits in a Drosophila cell line. Whereas the Drosophila nAChR β subunit (SBD) cDNA, reported previously, lacked part of the SBD coding sequence, here we report the construction and expression of a full-length SBD cDNA. We have examined whether problems in expressing functional Drosophila nAChRs in either Xenopus oocytes or mammalian cell lines can be attributed to an inability of these expression systems to assemble correctly Drosophila nAChRs. Despite expression in what might be considered a more native cellular environment, we have been unable to detect functional nAChRs in a Drosophila cell line unless Drosophila nAChR subunit cDNAs are coexpressed with vertebrate nAChR subunits. Our results indicate that the folding of Drosophila nAChR subunits is temperature-sensitive and strongly suggest that the inability of these Drosophila nAChR subunits to generate functional channels in the absence of vertebrate subunits is due to a requirement for coassembly with as yet unidentified Drosophila nAChR subunits.