Cloning and Sequence of Nicotinic Acetylcholine Receptor α Subunit from Chilo suppressalis

Nicotinic acetylcholine receptors (nAChRs) play a significant role in excitatory synaptic transmission in insects and are the target for chloronicotinyl and nereistoxin insecticides.In recent years,Chilo suppressalis,an economically important pest of rice,developed high resistance against monosultap,a nereistoxin insecticide acting on nAChR.In order to reveal the hypothesized target insensitive mechanism,studies on the molecular property of nAChR from Chilo suppressalis are required.In this study,the full length cDNA of nAChR α subunit from this pest was cloned by RT-PCR.Sequence analysis shows that it is a novel nAChR α subunit,which was named as Cs α 1(Genbank accession No.AF418987).It contains 1?997?bp nucleotides and involves an open reading frame (ORF) encoding a mature protein of 509 amino acids excluding a signal peptide of 24 amino acids.The deduced amino acid sequence was 52%-94% identical to the reported insect nAChR genes.

基于α7nAChRs的针刺对慢性偏头痛大鼠抗炎作用的研究

目的探讨针刺对慢性偏头痛(Chronic Migraine,CM)大鼠α7烟碱型乙酰胆碱受体(α7 nicotinic acetylcholine receptors,α7nAChRs)影响炎症变化的作用。方法将成年雄性SD大鼠根据基础痛阈随机分为对照组(VEH组)、模型组(NTG组)、模型+针刺组(TA组)、模型+针刺+α7nAChRs拮抗剂MLA组(MLA组)、模型+α7nAChRs激动剂PNU-282987组(PNU组)。采用隔日颈背部皮下重复注射硝酸甘油(NTG)建立CM大鼠模型。TA组和MLA组于NTG注射前1 h针刺,20 min/天,连续9天。MLA组于针刺前0.5 h腹腔注射MLA,PNU组于NTG注射前0.5 h腹腔注射PNU-282987,连续9天。采用Von Frey和热辐射测痛仪检测各组大鼠足底机械痛阈值(Paw Withdrawal Mechanical Threshold,PWMT)和甩尾潜伏期(Tail-Flick Latency,TFL)的变化;ELISA法检测各组大鼠血清及TNC中炎性因子IL-1β、TNF-α和TGF-β含量;免疫荧光双标法检测TNC中GFAP和α7nAChRs的平均光密度和共表达情况。结果与VEH组相比,NTG组PWMT、TFL明显降低(P<0.05或P<0.01),血清和TNC中IL-1β(P<0.01)、TNF-α(P<0.01,P<0.05)含量明显增多,TNC中AS明显活化(P<0.01),而α7nAChRs平均光密度和GFAP与α7nAChRs共表达明显减少(P<0.05,P<0.01);与NTG组相比,TA组PWMT、TFL升高(P<0.05或P<0.01),血清和TNC中IL-1β(P<0.01)、TNF-α(P<0.01,P<0.05)含量增多,TNC中GFAP平均光密度明显降低(P<0.01),而α7nAChRs平均光密度和GFAP与α7nAChRs共表达明显增加(P<0.01);与MLA组比较,TA组和PNU组PWMT、TFL明显升高(P<0.05或P<0.01),TA组血清和TNC中IL-1β(P<0.05)、TNF-α(P<0.01)含量增多而TGF-β(P<0.05)含量减少,PNU组血清和TNC中IL-1β含量减少(P<0.01,P<0.05)而TGF-β(P<0.01)含量明显增多。结论针刺能够有效缓解CM炎症反应和痛觉超敏状态,其抗炎镇痛效应可能与上调α7nAChRs的表达有关。

激活α7nAchR促进肥胖小鼠的脂肪稳态和米色脂肪生成及产热作用

目的观察肥胖小鼠脂肪组织形态学改变以及脂代谢、炎症等相关指标的异常表现,探索激活α7烟碱型乙酰胆碱受体(α7 nAchR)促进肥胖机体白色脂肪米色化产热的作用机制。方法取诱导成肥胖小鼠40只和10只低脂进食小鼠,分为空白组、高脂组、模型组、激动剂组、抑制剂组(10只/组)。苏木素-伊红(HE)染色观察小鼠附睾白色脂肪组织,评估细胞数量、大小及形态。ELISA检测白色脂肪组织肿瘤坏死因子(TNF-α)、白细胞介素-1(IL1β)、白细胞介素10(IL10)、转化生长因子-β(TGF-β)表达水平。qRT-PCR检测白色脂肪一氧化氮合酶(iNOS)、精氨酸酶1(Arg1)mRNA。PCR检测解偶联蛋白(UCP-1)、PR结构域蛋白16(PRDM-16)、线粒体生成的关键调节因子(PGC-1α)mRNA水平。Western blot检测白色脂肪核转录因子P65(NF-κB P65)、磷酸化蛋白酪氨基酸激酶2(p-JAK2)、磷酸化传导及转录激活因子3(p-STAT3)表达水平。结果与空白组比较,高脂组体质量明显增加(P<0.01),白色脂肪组织中出现较多脂肪空泡,脂滴明显增大,iNOS mRNA及TNF-α、IL-1β水平升高(P<0.01),而Arg-1 mRNA及IL-10、TGF-β水平降低(P<0.01);而与模型组相比,药物干预的3组体质量均有所减轻(P<0.05),白色脂肪中脂滴缩小。激动剂组白色脂肪中PRDM-16、PGC-1α、UCP-1 mRNA下降最为明显。而激动剂组TNF-α、IL-1β水平降低(P<0.05,P<0.01),IL-10、TGF-β水平升高(P<0.01),M1/M2巨噬细胞比值降低。结论激活α7 nAchR后可以改善应用β3受体激动剂产生的白色脂肪组织稳态受损,促进白色脂肪中M1型巨噬细胞向M2型巨噬细胞转化减轻白色脂肪炎症反应,促进白色脂肪组织米色化,提高米色化产热效能。

Identification of α7 nicotinic acetylcholine receptor on hippocampal astrocytes cultured in vitro and its role on inflammatory mediator secretion

The present study found expressions of a7 nicotinic acetylcholine receptor on hippocampal slices and hippocampal astrocytes using double immunofluorescence stainings. Expression of glial fibdllary acidic protein in the cultured hippocampal slices and hippocampal astrocytes significantly increased, and levels of macrophage inflammatory protein la, RANTES, interleukin-1β, intedeukin-6, and tumor necrosis factor-α increased in the supernatant of cultured astrocytes following exposure to 200 nM amyloid 13 protein 1-42. Preconditioning of 10 μM nicotine, a nicotinic acetylcholine receptor agonist, could attenuate the influence of amyloid β protein 1-42 in inflammatory mediator secretion of cultured astrocytes. Experimental findings indicated that α7 nicotinic acetylcholine receptor was expressed on the surface of hippocampal astrocytes, and activated a7 nicotinic acetylcholine receptor was shown to inhibit inflammation induced by amyloid β protein 1-42.

Possible implications of dysregulated nicotinic acetylcholine receptor diffusion and nanocluster formation in myasthenia gravis

Myasthenia gravis is a rare and invalidating disease affecting the neuromuscular junction of voluntary muscles.The classical form of this autoimmune disease is characterized by the presence of antibodies against the most abundant protein in the neuromuscular junction,the nicotinic acetylcholine receptor.Other variants of the disease involve autoimmune attack of non-receptor scaffolding proteins or enzymes essential for building or maintaining the integrity of this peripheral synapse.This review summarizes the participation of the above proteins in building the neuromuscular junction and the destruction of this cholinergic synapse by autoimmune aggression in myasthenia gravis.The review also covers the application of a powerful biophysical technique,superresolution optical microscopy,to image the nicotinic receptor in live cells and follow its motional dynamics.The hypothesis is entertained that anomalous nanocluster formation by antibody crosslinking may lead to accelerated endocytic internalization and elevated turnover of the receptor,as observed in myasthenia gravis.

Targeting α7 nicotinic acetylcholine receptors: a future potential for neuroprotection from traumatic brain injury

Traumatic brain injury （TBI） poses a significant socioeconomic burden in the world. The long lasting consequences in cognitive impairments are often underreported and its mechanisms are unclear. In this perspective, cholinergic dysfunction and thera-peutic strategy targeting this will be reviewed. Novel agents that can target specific subtype of acetylcholine receptors have been developed over the recent years and are at various stages of development, which include AR-R 17779, GTS-21, SSR- 180711A, AR-R17779, and PNU-282987. A detailed review on this topic has been previously published （Shin and Dixon, 2015）.

基于α7nAChR/NF-κB通路研究点按脾俞、胃俞穴对缓解慢性疲劳综合征大鼠外周炎症的效应机制

目的观察点按脾俞、胃俞穴对慢性疲劳综合征(chronic fatigue syndrome,CFS)模型大鼠疲劳状态、运动行为、外周炎症及α7烟碱型乙酰胆碱受体(α7 nicotinic acetylcholine receptor,α7nAChR)/核因子κB(nuclear factor-κB,NF-κB)信号表达的影响,探讨点按脾俞、胃俞穴对缓解CFS大鼠外周炎症的效应机制。方法先将32只SD大鼠随机分为空白组(8只)和造模组(24只)。造模组采用强迫负重游泳联合慢性应激刺激的方法建立CFS大鼠模型。造模成功后,将造模组大鼠随机分为模型组、点按组、α7nAChR激动剂组,每组8只。空白组、模型组予腹腔注射等体积生理盐水;点按组以自制按法刺激仪点按双侧脾俞、胃俞穴,20 min/次,并予腹腔注射等体积生理盐水;α7nAChR激动剂组予腹腔注射α7nAChR激动剂PNU-282987(每次2.4 mg/kg)。每组每日干预1次,连续14 d。记录各组大鼠一般情况半定量评分、力竭游泳时间和旷场实验运动距离;计算大鼠脾脏指数和胸腺指数;采用ELISA法检测大鼠血清中肿瘤坏死因子-α(tumor necrosis factor-α,TNF-α)、白细胞介素-1β(interleukin-1β,IL-1β)、白细胞介素-6(interleukin-6,IL-6)的含量;Western blot检测大鼠脾脏组织α7nAChR、NF-κB p65、NF-κB p-p65、TNF-α的蛋白表达水平;采用qPCR法检测α7nAChR、NF-κB p65、TNF-α的mRNA表达水平。结果与空白组比较,模型组一般情况半定量评分,血清TNF-α、IL-1β、IL-6含量,脾脏组织中NF-κB p-p65、NF-κB p65、TNF-α蛋白表达水平及NF-κB p65、TNF-αmRNA表达量均升高(P<0.01);力竭游泳时间、旷场实验运动距离、脾脏指数、胸腺指数、脾脏组织中α7nAChR蛋白表达水平及mRNA表达量均降低(P<0.05,P<0.01)。与模型组比较,点按组与α7nAChR激动剂组一般情况半定量评分,血清TNF-α、IL-1β、IL-6含量,脾脏组织中NF-κB p-p65、NF-κB p65、TNF-α蛋白表达水平及NF-κB p65、TNF-αmRNA表达量均降低(P<0.05,P<0.01);力竭游泳时间、旷场实验运动距离、脾脏指数、胸腺指数、脾脏组织中α7nAChR蛋白表达水平及mRNA表达量均升高(P<0.05,P<0.01)。与点按组比较,α7nAChR激动剂组血清TNF-α、IL-1β、IL-6含量,脾脏组织中NF-κB p-p65、NF-κB p65、TNF-α蛋白表达水平及NF-κB p65、TNF-αmRNA表达量均降低(P<0.01),脾脏组织中α7nAChR蛋白表达水平及mRNA表达量均升高(P<0.05,P<0.01)。结论点按脾俞、胃俞穴可有效改善CFS大鼠的疲劳状态和运动行为,提高免疫水平并缓解外周炎症,这可能与激活α7nAChR的表达,从而抑制NF-κB下游炎性通路的活性相关。

Activities of nicotinic acetylcholine receptors modulate neurotransmission and synaptic architecture

The cholinergic system is involved in a broad spectrum of brain function, and its failure has been implicated in Alzheimer＇s disease. Acetylcholine transduces signals through muscarinic and nicotinic acetylcholine receptors, both of which influence synaptic plasticity and cognition. However, the mechanisms that relate the rapid gating of nicotinic acetylcholine receptors to persistent changes in brain function have remained elusive. Recent evidence indicates that nicotinic acetylcholine receptors activities affect synaptic morphology and density, which result in persistent rearrangements of neural connectivity. Further investigations of the relationships between nicotinic acetylcholine receptors and rearrangements of neural circuitry in the central nervous system may help understand the pathogenesis of Alzheimer＇s disease.

α7nAChR抑制MyD88依赖性Zonulin释放改善脑梗死大鼠肠道炎症和肠屏障损伤

目的:观察α7型烟碱乙酰胆碱受体(α7nAChR)激动剂PNU282987对脑梗死大鼠肠道炎症和肠屏障损伤的影响。方法:将36只雄性SD大鼠随机分为假手术(sham)组、中脑动脉栓塞(MCAO)组和PNU282987组。MCAO组和PNU282987组采用Longa改良线栓法制备MCAO模型,PNU282987组腹腔注射1 mg/kg PNU282987,连续7 d。苏木精—伊红(HE)染色观察肠道黏膜病理改变,酶联免疫吸附试验(ELISA)检测结肠组织肿瘤坏死因子(TNF-α)、白细胞介素(IL-6)水平及血清二胺氧化酶(DAO)、D-乳酸(DLA)、内毒素(ET)水平,免疫组化法检测结肠组织Toll样受体2(TLR2)蛋白表达,western blotting法检测结肠组织紧密连接关键蛋白咬合蛋白(Occludin)、闭合蛋白(Claudin-1)、连蛋白(Zonulin)、带状闭合蛋白(ZO-1)、TLR2、髓样分化因子88(MyD88)、核因子-κB(NF-κB)和磷酸化NF-κB(p-NF-κB)蛋白表达。结果:与sham组比较,MCAO组大鼠肠上皮脱落、肠绒毛排列紊乱及黏膜下层炎性浸润,血清DAO、DLA、ET水平及结肠组织TNF-α、IL-6含量显著增高,结肠组织Occludin、Claudin-1、ZO-1蛋白表达显著下调,Zonulin、TLR2、MyD88、p-NF-κB蛋白表达显著上调(均P<0.05)。与MCAO组比较,PNU282987组大鼠肠上皮损伤减轻,血清DAO、DLA、ET水平及结肠组织TNF-α、IL-6含量显著降低,结肠组织Occludin、Claudin-1、ZO-1蛋白表达显著上调,Zonulin、TLR2、MyD88、p-NF-κB蛋白表达显著下调(均P<0.05)。结论:PNU282987可以显著改善脑梗死大鼠肠道炎症及肠屏障损伤,其机制可能与抑制TLR2/MyD88/NF-κB信号通路有关。

Differentiation of the Agonists and Antagonists of the α7 Nicotinic Acetylcholine Receptor

Theα7 nicotinic acetylcholine receptors(nAChRs)are widely expressed in the central and peripheral nervous systems and are important drug targets for the treatment of neurological diseases.However,differentiation of the agonists and antagonists of the nAChR is difficult.In this study we aimed to develop a reliable and efficient computational approach for differentiation of the agonists from the antagonists of the nAChR based on a systematical analysis of 123 ligands(87 agonists,12 partial agonists,and 24 antagonists)binding with the extracellular domain of theα7 n AChR chimera.Our results suggest that the ligand size and ligand binding affinity cannot differentiate the agonists from the antagonists of the nAChR.The ligand efficiency that considers both ligand binding affinity and size for the agonists is overall more left shifted in comparison to the antagonists,but the values of the ligand efficiency still cannot differentiate the agonists from the antagonists unless the values are either relatively high(more than-0.3 kcal mol^-1)or relatively low(less than-0.45 kcal mol^-1).Our results suggest that accurate prediction of the agonist or antagonist of the nAChR is challenging and the ligand innate configuration has to be considered as an extra for differentiation of the agonists from the antagonists of the nAChR.

Effect of soman,sarin and VX on the nicotinic acetylcholine receptor

The highly specific ligand of the N-acetylcholine receptor（N-AChR）,alpha-bungarotoxin,was used to determine the effect of soman,sarin and VX onN-AChR of the diaphragm and extensor digitorum Iongus muscle of mice andrats.The effects of the three anti-cholinesterase agents on N-AChR weredifferent.Sarin did not act directly on N-AChR and cause a change in the numberof N-AChR.VX decreased the binding sites of the receptor by binding with N-AChRdirectly.The LD50was 0.054mg/kg in mousse.Soman increased the binding sites,e.g.1～1.5 LD50soman increased the number of N-AChR of mouse diaphragm by 25%.The peak increaseof N-AChR was reached 0.5 h after poisoning and could last 96h.The receptornumber was still 22% higher than that of the control on the fourth day aftersoman poisoning in rats.Soman mainly increased the number of extrasynapticN-AChR,leading to the enhancement of sensitivity of cholinergic effectors toacetylcholine（ACh）,which is similar to the hypersensitiveness resulting fromdenervation.These findings are of significance in probing the receptor mecha-nisms and treatment of soman poisoning.

Effect of differential rearing environments on nicotine-stimulated locomotor activity and nicotinic acetylcholine receptor subtypes

OBJECTIVE Individuals vary in sensitivity to the behavioral effects of nicotine,resulting in differences in their vulnerability to addiction.The role of rearing environment in determining individual sensitivity to nicotine is unclear.The neuropharmacological mechanisms mediating the effect of rearing environment on the actions of nicotine are also understood.Thus,the contribution of rearing environment in determining the sensitivity to the locomotor effects of nicotine and regulating α4β2*-and α7-nicotinic acetylcholine(n ACh) receptor expressionwas determined in rats reared in isolated(IC) or enriched(EC) conditions.METHODS To measure locomotor activity,adolescent rats(postnatal day 21-51)were injected with saline(1 mL·kg^(-1)) or nicotine(0.3 mg·kg^(-1)) subcutaneously,then placed in chamberswhere ambulatory activity was monitored for 30-min by computer for 14 daily sessions.α4β2*-andα7-n ACh receptor expression in the mesolimbic dopamine pathway was determined by quantitative autoradiography of [125 I]-epibatidine and [125 I]-bungarotoxinbinding,respectively,in 16 μmol·L^(-1) coronal sections.Values for receptor expression in fmol are ±s of 8 brains and compared by two-tailed,unpaired t-test with P<0.05 considered significant.RESULTS EC-rats are similarly sensitive as IC-rats to the locomotor effects of nicotine.[125 I]-epibatidine binding in the ventral tegmental area of EC-rats was reduced(2.8±0.3 fmo L) compared to IC-rats(4.0±0.4 fmo L);there was no difference in the nucleus accumbens.There was no difference between EC-and IC-rats in α7-n ACh receptor expression in the mesolimbic dopamine pathway.CONCLUSION Rearing environment differentially regulates n ACh receptor subtypes in EC and IC rats.These data suggest regulation of n ACh receptors by environmental factors may be a mechanism for the protective effect of enrichment against altered sensitivity to nicotine in genetically vulnerable individuals.The characterization of these mechanisms will aid in development of novel pharmacological tools mimicking the protection afforded by environmental enrichment in nicotine-sensitive individuals.

Enzyme-linked Immunosorbent Assay for Detection of Anti-idiotype Antibodies to Antibodies to Ligand of Nicotinic Acetylcholine Receptor in Sera of Patients with Myasthenia Gravis

Anti-bungarotoxin anti-serum,which has the internal image of nicotinicacetylcholine receptor,was used as a tool to measure anti-idiotypic antibodies toantibodies to Iigand of nicotinic acctylcholine receptor in scra from 81 patients withmyasthenia gravis.Enzyme-linked immunosorbcnt assay was adopted.Thc positive ratewas 46.9%(38/81).The specific cross inhibitory test with nicotinic acetylcholinereceptor was positive.Anti-idiotype antibodies to antibodies to ligand of nicotinicacetylcholine receptor in sera of different types of myasthenia gravis patients classified ac-cording to modified Osserman’s standard and myasthenia gravis patients with or withoutthymoma were comparcd in this study and the role of anti-idiotype antibodies toantibodies to Iigand of nicotinic acctylcholinc receptor in the immunity of myasthcniagravis and the possibility of thcrapeutic use of anti-idiotype antibodies arc discussed.

Nicotinic Acetylcholine Receptor Gene Family of the Pea Aphid,Acyrthosiphon pisum

The nicotinic acetylcholine receptors （nAchRs） are cholinergic receptors that form ligand-gated ion channels by ifve subunits in insect and vertebrate nervous systems. The insect nAChR is the molecular target of a class of insecticides, neonicotinoids. Here, we identiifed and cloned 11 candidate nAChR subunit genes in Acyrthosiphon pisum using genome-based bioinformatics combined modern molecular techniques. Most A. pisum nAChRs including α1, α2, α3, α4, α6, α8, and β1 show highly sequence identities with the counterparts of other insects examined. Expression proifles analysis showed that all subunit genes were expressed in adult head. At least two subunits have alternative splicing that obviously increase A. pisum nicotinic receptor diversity. This study will be invaluable for exploring the molecular mechanisms of neonicotinoid-like insecticides in sucking pests, and for ultimately establishing the screening platform of novel insecticides.

Computational Determination of the Binding Mode of α-Conotoxin to Nicotinic Acetylcholine Receptor

Abstract Conotoxins belong to the large families of disulfide-rich peptide toxins from cone snail venom, and can act on a broad spectrum of ion channels and receptors. They are classified into different subtypes based on their targets. The a-conotoxins selectively inhibit the current of the nicotinic acetylcholine receptors. Because of their unique selectivity towards distinct nAChR subtypes, a-conotoxins become valuable tools in nAChR study. In addition to the X-ray structures of a-conotoxins in complex with acetyleholine-binding protein, a homolog of the nAChR ligand-binding domain, the high-resolution crystal structures of the extracellular domain of the al and a9 subunits are also obtained. Such structures not only revealed the details of the configuration of nAChR, but also provided higher sequence identity templates for modeling the binding modes of a-conotoxins to nAChR. This mini-review summarizes recent modeling studies for the determination of the binding modes of a-conotoxins to nAChR. As there are not crystal structures of the nAChR in complex with conotoxins, computational modeling in combination of mutagenesis data is expected to reveal the molecular recognition mechanisms that govern the interactions between a-conotoxins and nAChR at molecular level. An accurate determination of the binding modes of a-conotoxins on AChRs allows rational design of a-conotoxin analogues with improved potency or selectivity to nAChRs.

Activation of α7 nicotinic acetylcholine receptor protects against oxidant stress damage through reducing vascular peroxidase-1 in a JNK signaling-dependent manner in endothelial cells

Aim Alpha7 nicotinic acetylcholine receptor （α7nAChR）, a subtype of nAChR regulating neurotrans- mission in central nervous system, is an essential regulator of cholinergic antiinflammatory pathway in periphery. The present study was to determine the effects of activation of α7nAChR on oxidant stress-induced injury in endo- thelial cells. Methods Cultured human umbilical vein endothelial cells were treated with H202 （400 μmol · L^-1） or H202plus PNU-282987 （ 10 μmol · L^-1 ）. Cell viability and membrane integrity were measured. AnnexinV ＋ PI assay, immunoblotting of bcl-2, bax and cleaved caspase-3, and immunofluorescence of apoptosis inducing factor （AIF） were performed to evaluate apoptosis. Protein expression of vascular peroxidase-1 （ VPO-1 ） and phosphor- JNK were measured by immunoblotting. Results Activation of α7nAChR by a selective agonist PNU-282987 pre-vented H202-indced decrease of cell viability and increase of lactate dehydrogenase release. Activation of α7nAChR markedly reduced cell apoptosis and intracellular oxidative stress level. Moreover, activation of α7nAChR reduced H2 02 -induced VPO-1 protein upregulation and JNK1/2 phosphorylation. The inhibitory effect of α7nAChR activa- tion on VPO-1 was blocked by JNK inhibitor SP600125. In addition, pretreatment of α7nAChR antagonist methyl- lycaconitine blocked the cytoprotective effect of PNU-282987. Conclusion These results provide the first evidence that activation of α7nAChR protects against oxidant stress-induced damage by suppressing VPO-1 in a JNK signa- ling pathway-dependent manner in endothelial cells.

Nanoscale interactions between the nicotinic acetylcholine receptor and cholesterol

Cholesterol is a major lipid in biological membranes.It not only plays a structural role but also modulates a wide range of functional properties of neurotransmitter and hormone receptors and ion channels.The membraneembedded segments of the paradigm neurotransmitter receptor for acetylcholine(nAChR)contain linear sequences of amino acids with the capacity to recognize cholesterol.These cholesterol consensus domains have been designated as“CARC”and its mirror sequence“CRAC”.CARC preferentially occurs in the exoplasmic-facing membrane leaflet,and CRAC,in the cytoplasmic-facing hemilayer.Both motifs are highly conserved among ion-channel and neurotransmitter receptor proteins in vertebrate nervous systems,where they recognize cholesterol,and in prokaryotic homologues in bacteria,where they recognize hopanoids.This phylogenetically conserved trait is an indication that the hopanoids in some bacteria and cholesterol in eukaryotes subserve analogous functions,probably contributing to the stability of membrane-embedded protein domains.Structural studies from our laboratory using superresolution optical microscopy(“nanoscopy”)have disclosed other interrelated functional and structural properties exerted by cholesterol on the nAChR.The neutral lipid content at the cell surface influences both the macromolecular organization of the receptor and its translational mobility(diffusion)in the plane of the membrane.

Attenuation of nicotine-evoked Ca²⁺influx by antibody to the nicotinic acetylcholine receptor <i>α</i>3 subunits in human embryonic kidney cells

Autoantibody against neuronal nicotinic acetylcholine receptor (nAChR) α3 subunit is implicated in severe autonomic dysfunction in the patients with autoimmune autonomic ganglionopathy (AAG). Although this autoantibody has been revealed to impair fast excitatory synaptic transmission in autonomic ganglia, its precise mechanism remains unknown. Here, we show that antibody-induced reduction of cell-surface α3 subunits result in impairment of nicotine-evoked Ca2+ influx in stably transfected human embryonic kidney cells. These effects of the antibody were remarkably inhibited by interfering with the endocytic machinery at low-temperature. We conclude that reduction of nAChR in autonomic ganglia can be mediated by the endocytosis of α3 subunits, and resulted in autonomic failure in AAG patients.

Synthesis of 2-[^(18)F]fluoro-3-[2(S)-2-azetidinylmethoxy]pyridine as a radioligand for imaging nicotinic acetylcholine receptors

Nicotinic acetylcholine receptors(nChRs) are involved in the various pharmacological effects or disease states.In order to study the central nChRs by PET or SPECT,some radioligands have been investigated.In this paper,the procedure for synthesis of 2-[^18F] fluoro-3-[2(S)-2-azetidinylmethoxy]pyridine(2-[^18F0-A-85380),a potential PET ligand for in vivo imaging nicotinic acetylcholine receptor was described.2-[^18F]-A-85380 was prepared from the precursor,2-nitro-3-[(1-(tert-butoxycarbonyl)-2-(S0-azetidinyl)methoxy] pyridine(4),which was synthesized with commercial (S)-2-zaetid-inecarboxylic acid as starting material.The whole procedure for radiosynthesis and purification was executed in about 1h and 45-55% of the added fluorine-18 was found in the purified 2-[^18F]-A-85380,with specific activity of 1.0-2.2×10^11 Bq/umol.

Homology Model and Ligand Binding Interactions of the Extracellular Domain of the Human α4β2 Nicotinic Acetylcholine Receptor

Addiction to nicotine, and possibly other tobacco constituents, is a major factor that contributes to the difficulties smokers face when attempting to quit smoking. Amongst the various subtypes of nicotinic acetylcholine receptors (nAChRs), the α4β2 subtype plays an important role in mediating the addiction process. The characterization of human α4β2-ligand binding interactions provides a molecular framework for understanding ligand-receptor interactions, rendering insights into mechanisms of nicotine addiction and may furnish a tool for efficiently identifying ligands that can bind the nicotine receptor. Therefore, we constructed a homology model of human α4β2 nAChR and performed molecular docking and molecular dynamics (MD) simulations to elucidate the potential human α4β2-ligand binding modes for eleven compounds known to bind to this receptor. Residues V96, L97 and F151 of the α4 subunit and L111, F119 and F121 of the β2 subunit were found to be involved in hydrophobic interactions while residues S153 and W154 of the α4 subunit were involved in the formation of hydrogen bonds between the receptor and respective ligands. The homology model and its eleven ligand-bound structures will be used to develop a virtual screening program for identifying tobacco constituents that are potentially addictive.