D2型多巴胺受体配基的研究进展

阐述了近几年D2型受体配基的研究状况，探讨了部分具有应用前景的化合物的构效关系。特别指出混合受体拮抗剂(如d2／d4、d2／5HTlA)和部分激动剂可能成为新的非经典抗精神失常药物，而兼有抗氧化作用的多巴胺受体激动剂则成为抗帕金森病药物研究的主要方向。     

新型多巴胺D2类受体部分激动剂brexpiprazole

在多巴胺D2类受体中,D2受体部分激动剂对中脑边缘通路可产生功能性拮抗作用,能有效的改善精神分裂症因D2过度活动引起的阳性症状;对中脑皮层通路可产生功能性激动作用,可改善D2功能低下所引起的阴性症状、认知损害。brexpiprazole是一种新型多靶点作用机制的用于精神障碍疾病的治疗药物,除主要具备多巴胺D2受体部分激动作用之外,还具备D3受体部分激动作用、5-HT1A部分受体激动作用和5-HT2A部分受体拮抗作用,是针对单胺类神经递质多靶点开发的同时具有抗精神分裂和抗抑郁作用的新药,目前正在进行Ⅲ期临床试验。     

活化性受体NKG2D免疫监视作用研究新进展

<正>近年来,人们对活化性受体NKG2D免疫监视作用有了新的认识,包括其配体为压力诱导型分子,在应激如感染,细胞变异等条件下诱导表达,这为临床肿瘤免疫治疗提供了一种新的疗法——NKG2D及其配体介导的肿瘤免疫治疗。     

遵义地区人群维生素D受体基因外显子2多态性

目的探讨遵义地区人群维生素D受体（VDR）基因第2外显子（起始密码子,e2）的单核苷酸多态性分布情况。方法收集110例遵义地区汉族人群静脉血标本,采用聚合酶链反应．限制性片段长度多态性法测定VDR基因e2序列多态性．分析该人群中基因型频率和基因频率分布规律。结果FokI的等位基因频率为F0．741、f0．259。结论VDR基因e2序列在遵义地区汉族中的分布具有多态性。     

THPBs同类物对多巴胺D1、D2、D3受体的作用特性

目的：左旋千金藤啶碱（1-SPD）是四氢原小檗碱同类物（THPBs）的先导化合物，本课题组已证明其具有D1受体激动和D2受体阻滞的双重作用，并积极倡导D1激动-D2阻滞双重作用与精神分裂症病因相匹配治疗的设想。新近又发现SPD对D3受体有较强的亲和力，因此本研究SPD的更理想的结构关系。国际上新发现D3受体与精神分裂症、帕金森病和药物成瘾的发病过程均有密切关系。方法：利用体外基因表达技术，构建了表达D1受体、D2受体、D3受体的Sf9细胞和稳定表达D3受体的NG108细胞。     

维生素D受体基因BsmI多态性与2型糖尿病关系研究

目的探讨维生素D受体（VDR）基因BsmI位点多态性与2型糖尿病（DM2）的关系。方法运用聚合酶链式反应．限制性片段长度多态性分析（PCR-RFLP）技术检测66例2型糖尿病（DM2）患者,80例健康人的维生素D受体（VDR）基因BsmI位点基因型．分析比较两组间等位基因及基因型频率分布差异。结果DM2组患者BB＋Bb基因型及B等位基因频率显著高于正常对照组（P=0．001,OR=5．625;P=0．000。OR=6．541）。结论VDR．BsmI基因与DM2患者发病相关,“B”等位基因是DM2发病的易感因素。     

天津地区汉族人2型糖尿病与维生素D受体基因多态性的研究

目的:探讨天津地区汉族人2型糖尿病(T2DM)与维生素D受体(VDR)基因多态性的关系。方法:采用聚合酶链反应-限制性酶切片段长度多态性分析方法测定116例T2DM患者和112例正常对照者的VDR-Fok1和VDR-Bsm1位点基因型,计算并比较T2DM患者和正常对照组基因型频率。结果:T2DM患者与正常对照组VDR-Fok1位点基因型、F/f等位基因的分布差异无统计学意义(P>0.05);VDR-Bsm1位点基因型、B/b等位基因的分布差异有统计学意义,T2DM患者VDR-Bsm1位点Bb基因型、B等位基因明显增加(P<0.01)。结论:VDR基因Bsm1位点Bb基因型、B等位基因可能是天津地区汉族人T2DM的基因型和易感基因。     

活化型受体NKG2D及其配体在肿瘤免疫中的作用

自然杀伤（NK）细胞和T细胞是主要的抗肿瘤免疫效应细胞,在肿瘤免疫监视中发挥着重要作用。近年来由于NKG2D及其配体的发现,对NK细胞抗肿瘤分子机制有了更进一步认识,从而为开发新的抗肿瘤免疫治疗开辟了新的道路。NKG2D不仅在所有的NK细胞上表达,     

多巴胺D_2/血管紧张素AT_1嵌合受体:D_2受体第三细胞内环影响受体与配基结合以及与G蛋白偶联的特性(英文)

目的:研究受体第三细胞内环(IL_3)的长度对受体与配基结合及与G蛋白偶联特性的影响.方法:用目前已知的G蛋白偶联受体中IL_3最短的血管紧张素Ⅱ AT_1受体的IL_3替换野生型D_2受体较长的IL_3,组成D_2/AT,嵌合受体.结果:与野生型D_2受体相比,D_2/AT_1嵌合受体与拮抗剂的亲和性均降低,与激动剂的亲和性有的增高,有的降低.嵌合受体失去与G蛋白偶联的能力,也不能产生磷酸肌醇水解.结论:受体的IL_3对受体配基结合位点和空间构象有一定影响;受体与G蛋白的偶联不仅与IL_3有关,而且还受非IL_3区域的影响,而IL_3的长度是决定这两方面影响的因素之一.     

Delineation of muscarinic receptor domains conferring selectivity of coupling to guanine nucleotide-binding proteins and second messengers

The cloning and functional expression of five mammalian muscarinic acetylcholine receptor genes (m1-m5) has revealed that m1, m3, and m5 primarily couple to stimulation of phosphoinositide (PI) turnover, whereas m2 and m4 are strongly linked to inhibition of adenylate cyclase, albeit not exclusively. To identify the structural domains responsible for this functional specificity, cDNAs encoding chimeric m2/m3 receptors were constructed. The abilities of these receptors to mediate stimulation of PI hydrolysis and inhibition of prostaglandin E2-stimulated cAMP accumulation, as well as the pertussis toxin (PTX) sensitivity of these responses, were examined after stable expression in mouse A9 L cells. Substitution of the putative third cytoplasmic loop (i3) of m2 with the corresponding m3 sequence resulted in a chimeric receptor that, similar to m3, stimulated PI breakdown by a PTX-insensitive mechanism but did not inhibit adenylate cyclase. Conversely, a chimeric m3 receptor containing the i3 domain of m2 showed the same functional profile as m2 (i.e., inhibition of adenylate cyclase and weak stimulation of PI turnover by a PTX-sensitive mechanism), indicating that the i3 loop is sufficient to determine coupling selectivity. Similarly, exchange of a short N-terminal segment of i3 (16 or 17 amino acids) between m2 and m3 resulted in chimeric receptors that gained the ability to mediate the functional responses of the wild-type receptor from which the segment was derived, although with substantially reduced efficiency. However, the chimeric m2 receptor containing the 17-amino acid m3 sequence in the N-terminal portion of i3 retained its ability to inhibit adenylate cyclase. Carbachol binding studies involving the use of the GTP analog 5'-guanylyl imidodiphosphate and PTX-pretreated cells generally correlated well with the functional findings. Our data indicate that the N-terminal portion of i3 is a sufficient but not the exclusive determinant of coupling selectivity displayed by the various muscarinic receptors.     

Mono- and divalent cations modulate the affinities of brain D1 and D2 receptors for dopamine by a mechanism independent of receptor coupling to guanyl nucleotide binding proteins

Summary In order to clarify the question of whether the modulatory effects of cations on dopamine receptor affinities are brought about by shifts in the equilibrium of receptor — G-protein — coupling, it was investigated whether mono- and divalent cations were still able to modulate rat striatal D1 and D2 receptor affinities after selective inactivation of the G-proteins linked to the two receptors. The G_S-protein coupled to the D1 receptor was eliminated by mild thermal inactivation, and the G_i- (or G_o-) protein associated with the D2 receptor by alkylation with a low concentration of N-ethyl-maleimide. Incubation of striatal membranes at 60°C completely abolished the specific binding of³H-GTP. Both treatments resulted in an increase of the IC₅₀-values for dopamine as a displacer of³H-SCH 23390 from D1- and of³H-spiperone from D2 receptors. Concomitantly, the formerly shallow D1 displacement curves became steeper, with their Hill coefficients increasing. This effect was less evident at D2 receptors. Guanosine triphosphate (GTP), which increased the IC₅₀'s of dopamine for both receptors approximately two-fold in control membranes, was without effect in pretreated samples, indicating an effective inactivation of the G-proteins. Na⁺ ions were still able to lower, and Ca²⁺ ions to increase the affinities of D1 and D2 receptors for dopamine after such inactivation of the respective G-proteins. It is concluded that the mechanism underlying the regulation of dopamine receptor affinities by mono- and divalent cations is independent of and superimposed upon the coupling of these receptors to guanyl nucleotide binding proteins.Abbreviations ANOVA Analysis of variance; G-proteins, guanyl nucleotide binding proteins (G_s: stimulatory, G_i: inhibitory); - GTP guanosine-5-triphosphate; Gpp(NH)p, 5-guanylylimidodiphos-phate; - NEM N-ethyl-maleimide     

Reconstitution of the human 5-HT(1D) receptor-G-protein coupling: evidence for constitutive activity and multiple receptor conformations

The 5-hydroxytryptamine (5-HT) 1D/1B receptors have gained particular interest as potential targets for treatment of migraine and depression. G-protein coupling and other intrinsic properties of the human 5-HT(1D) receptor were studied using a baculovirus-based expression system in Sf9 cells. Coexpression of the human 5-HT(1D) receptor with Galpha(i1), alpha(i2), alpha(i3), or Galpha(o)-proteins and Gbeta(1)gamma(2)-subunits reconstituted a Gpp(NH)p-sensitive, high affinity binding of [(3)H]5-HT to this receptor, whereas the Galpha(q)beta(1)gamma(2) heterotrimer was ineffective in this respect. Competition of [(3)H]5-HT binding by various compounds confirmed that coexpression of the human 5-HT(1D) receptor with Galpha(i/o)beta(1)gamma(2) reconstitutes the receptor in a high affinity agonist binding state, having the same pharmacological profile as the receptor expressed in mammalian cells. Binding of the antagonist ocaperidone to the human 5-HT(1D) receptor in coupled or noncoupled state was analyzed. This compound competed with [(3)H]5-HT binding more potently on the human 5-HT(1D) receptor in the noncoupled state, showing its inverse agonistic character. Ocaperidone acted as a competitive inhibitor of [(3)H]5-HT binding when tested with the coupled receptor form but not so when tested with the noncoupled receptor preparation. Finally, [(35)S]GTPgammaS binding experiments using the inverse agonist ocaperidone revealed a high level of constitutive activity of the human 5-HT(1D) receptor. Taken together, the reconstitution of the human 5-HT(1D) receptor-G-protein coupling using baculovirus-infected Sf9 cells made possible the assessment of coupling specificity and the detection of different binding states of the receptor induced by G-protein coupling or ligand binding.     

Structural determinants of pharmacological specificity between D(1) and D(2) dopamine receptors

To test the hypothesis that pharmacological differentiation between D(1) and D(2) dopamine receptors results from interactions of selective ligands with nonconserved residues lining the binding pocket, we mutated amino acid residues in the D(2) receptor to the corresponding aligned residues in the D(1) receptor and vice versa and expressed the receptors in human embryonic kidney 293 cells. Determinations of the affinity of the 14 mutant D(2) receptors and 11 mutant D(1) receptors for D(1)- and D(2)-selective antagonists, and rhodopsin-based homology models of the two receptors, identified two residues whose direct interactions with certain ligands probably contribute to ligand selectivity. The D(1) receptor mutant W99(3.28)F showed dramatically increased affinity for several D(2)-selective antagonists, particularly spiperone (225-fold), whereas the D(2) receptor mutant Y417(7.43)W had greatly decreased affinity for benzamide ligands such as raclopride (200-fold) and sulpiride (125-fold). The binding of the D(1)-selective ligand R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (SCH23390) was unaffected, indicating that SCH23390 makes little contact with these ancillary pocket residues. Mutation of A/V(5.39) caused modest but consistent and reciprocal changes in affinity of the receptors for D(1) and D(2)-selective ligands, perhaps reflecting altered packing of the interface of helices 5 and 6. We also obtained some evidence that residues in the second extracellular loop contribute to ligand binding. We conclude that additional determinants of D(1)/D(2) receptor-selective binding are located either in that loop or in the transmembrane helices but, like residue 5.39, indirectly influence the interactions of selective ligands with conserved residues by altering the shape of the primary and ancillary binding pockets.     

The novel antidyskinetic drug sarizotan elicits different functional responses at human D2-like dopamine receptors

Sarizotan (EMD 128130) is a chromane derivative that exhibits affinity at serotonin and dopamine receptors. Sarizotan effectively suppresses levodopa-induced dyskinesia in primate and rodent models of Parkinson's disease, and tardive dyskinesia in a rodent model. Results from clinical trials suggest that sarizotan significantly alleviates levodopa-induced dyskinesia. The functional effects of sarizotan on individual dopamine receptor subtypes are not known. Here we report the functional effects of sarizotan on human D2-like dopamine receptors (D2S, D2L, D3, D4.2 and D4.4) individually expressed in the AtT-20 neuroendocrine cell line. Using the coupling of D2-like dopamine receptors to G-protein coupled inward rectifier potassium channels we determined that sarizotan is a full agonist at D3 and D4.4 receptors (EC50=5.6 and 5.4 nM, respectively) but a partial agonist at D2S, D2L and D4.2 receptors (EC50=29, 23 and 4.5 nM, respectively). Consistent with its partial agonist property, sarizotan is an antagonist at D2S and D2L receptors (IC50=52 and 121 nM, respectively). Using the coupling of D2-like dopamine receptors to adenylyl cyclase we determined that sarizotan is a full agonist at D2L, D3, D4.2 and D4.4 receptors (EC50=0.51, 0.47, 0.48 and 0.23 nM, respectively) but a partial agonist at D2S receptors (EC50=0.6 nM).     

Structure, function and regulation of the melanocortin receptors

Melanocortin receptors belong to the seven-transmembrane (TM) domain proteins that are coupled to G-proteins and signaled through intracellular cyclic adenosine monophosphate. Many structural features conserved in other G-protein coupled receptors (GPCRs) are found in the melanocortin receptors. There are five melanocortin receptor subtypes and each of the melanocortin receptor subtypes has a different pattern of tissue expression and has its own profile regarding the relative potency of different melanocortin peptides. α-, β-, and γ-MSH and ACTH are known endogenous agonist ligands for the melanocortin receptors. Agouti and AgRP are the only known naturally occurring antagonists of the melanocortin receptors. We have examined the molecular basis of all five human melanocortin receptors for different ligand binding affinities and potencies using chimeric and mutated receptors. Our studies indicate that human melanocortin MC₁ receptor, human melanocortin MC₃ receptor, human melanocortin MC₄ receptor and human melanocortin MC₅ receptor utilize orthosteric sites for non selective agonists, α-MSH and NDP-?α-MSH, high affinity binding and utilize allosteric sites for selective agonist or antagonist binding. Furthermore, our results indicate that molecular determinants of human melanocortin MC₂ receptor for ACTH binding and signaling are different from that of other melanocortin receptors. Many studies also indicate that agonists can induce different conformation changes of melanocortin receptors, which then lead to the activation of different signaling pathways, even when the expression level of receptor and the strength of stimulus–response coupling are the same. This finding may provide new information for the design of drugs for targeting melanocortin receptors.     

The influence of G protein subtype on agonist action at D2 dopamine receptors

In previous studies, we have shown that agonists influence the ability of D2 dopamine receptors to couple to G proteins and here we extend this work. The human D2Short dopamine receptor and a natural polymorphism of this D(2Short)(Ser311Cys), have been studied by co-expressing the receptors in insect cells with Gbeta1gamma2 and either Galpha(o), Galpha(i1), Galpha(i2) or Galpha(i3) G protein subunits. These preparations have been used to study the G protein coupling profiles of the two receptors and the influence of agonists. Receptor/G protein coupling was analysed in dopamine/[3H]spiperone competition binding experiments and through stimulation of [35S]GTPgammaS binding. Although the Ser311Cys polymorphism itself had no appreciable effect on the G protein coupling specificity of the D2 receptor, agonist stimulation of [35S]GTPgammaS binding, revealed that both dopamine and (+)-3PPP showed a clear preference for Galpha(o) compared to the Galpha(i) subtypes, but quinpirole did not. These results indicate that agonists are able to stabilise different receptor conformations with different abilities to couple to G proteins.     

Muscarinic allosteric modulation: M2/M3 subtype selectivity of gallamine is independent of G-protein coupling specificity

Among the five subtypes of muscarinic acetylcholine receptors, the sensitivity towards allosteric modulation is generally higher in M2 and M4 receptors that preferentially couple to inhibitory G-proteins of the Gi/o type than in M1, M3, and M5 that preferentially couple to stimulatory G-proteins such as Gq/11. We aimed to check whether the high allosteric sensitivity of the M2 receptor compared to M3 is related to the differential G-protein coupling preference. As the third intracellular loop (i3) is known to be the major determinant in receptor G-protein coupling specificity, we used wild-type M2 and M3 receptors and the related chimeric constructs with exchanged i3-loops, i.e., M2 containing M3-i3 (M2/M3-i3) and M3 containing M2-i3 (M3/M2-i3). The allosteric effect of the archetypal modulator gallamine on the dissociation and the equilibrium binding of [3H]N-methylscopolamine ([3H]NMS) was measured in membranes of mouse A9L cells stably expressing the wild-type and the chimeric receptors (4 mM Na2HPO4, 1 mM KH2PO4, pH 7.4, 23 degrees C). The dissociation of [3H]NMS was monophasic under all conditions studied. Control values of t 1/2 were (means +/- SEM, n = 4-7): M2: 3.8 +/- 0.2 min, M2/M3-i3: 4.8 +/- 0.3 min, M3:43.3 +/- 4.2 min, M3/M2-i3: 41.1 +/- 3.6 min. At M2 receptors, 0.2 microM gallamine allosterically reduced the apparent rate constant of dissociation k-1 to 51 +/- 5% of the control value (n = 5). At M2/M3-i3 the allosteric potency of gallamine was not significantly changed (0.2 microM gallamine --> k-1 = 61 +/- 4%, n = 7). At M3, a 20-fold higher concentration was required for an equieffective allosteric action (10 microM gallamine --> k-1 = 51 +/- 5%, n = 5). The potency of gallamine at M3/M2-i3 was not increased compared with M3 receptors (10 microM gallamine --> k-1 = 73 +/- 2%, n = 4) but even significantly diminished. [3H]NMS equilibrium binding experiments revealed that neither the binding constants of gallamine at free receptor subtypes (pKA,M2: 7.57 +/- 0.04, n = 4; pKA,M3: 5.56 +/- 0.13, n = 3) nor the factors of negative cooperativity with [3H]NMS (alphaM2 = 31 +/- 1, alphaM3 = 3 +/- 0.4) were affected by the exchanged i3-loops (pKA,M2/M3-i3: 7.65 +/- 0.03, pKA,M3/M2-i2: 5.35 +/- 0.24, alphaM2/M3-i3= 30 +/- 2, alphaM3/M2-i2 = 3 +/- 0.7). In conclusion, the different sensitivities of M2 and M3 receptors towards allosteric modulation by gallamine are not related to the G-protein coupling specificity of the receptors.     

Pharmacological characterization of regulation of phosphoinositide metabolism by recombinant 5-HT2 receptors of the rat.

Transfection of 5-HT2 receptor cDNA in 293 cells induced the expression of a protein binding domain, exhibiting the classical 5-HT2 receptor transduction mechanism. Both [3H]DOB and [3H]spiperone high affinity binding sites were present in membranes of sense but not of antisense, 5-HT2 receptor cDNA transfected cells. Addition of 1 microM 5-HT induced a time-dependent increase of phosphoinositide (PI) metabolism in sense but not in antisense, 5-HT2 receptor cDNA transfected cells. Graded concentrations of 5-HT and of different serotonergic agonists showed different potencies (DOI greater than 5-HT greater than quipazine greater than DOM greater than alpha-methyl-5-HT greater than 8-OH-DPAT greater than 2-methyl-5-HT greater than CGS-12066B) in stimulating turnover of PI in cells transfected with cDNA encoding for 5-HT2 receptors of the rat. The ability of different antagonists to inhibit 5-HT-stimulated turnover of PI bore a direct relationship with their potency to inhibit 5-HT2 receptor binding in cells transfected with 5-HT2 receptor cDNA (spiperone greater than ketanserin greater than ritanserin greater than mianserin greater than haloperidol). Preincubation of transfected 293 cells with pertussis toxin failed to modify either 5-HT- or DOI-induced activation of metabolism of PI. Pretreatment of transfected 293 cells with DOI (100 nM) for 2 hr or more, significantly reduced activation of turnover of PI elicited by graded doses of 5-HT. When the transfected 293 cells were exposed to DOI (100 nM) for 12 hr and the challenge was performed after a 2-hr wash-out period, the desensitization of the response to 5-HT was virtually abolished.(ABSTRACT TRUNCATED AT 250 WORDS)