Unaltered agonist potency upon inducible 5-HT7(a) but not 5-HT4(b) receptor expression indicates agonist-independent association of 5-HT7(a) receptor and Gs

We compared adenylyl cyclase (AC) activation by the G protein-coupled human serotonin (5-HT) receptors 5-HT4(b) and 5-HT7(a) using an ecdysone-inducible expression system, which allowed for reproducible expression of increasing receptor densities in clonal HEK293 (EcR293) cell lines. Low constitutive expression of receptors (2-70 fmol/mg protein) was observed and could be titrated up to 50-200-fold (approximately 400-7000 fmol/mg protein) by the ecdysone analogue ponasterone A. Although 5-HT-stimulated AC activity increased with receptor density, interclonal variation precluded comparisons of coupling efficiency. Interestingly, the potency of 5-HT to stimulate AC increased with increasing receptor density only in clones expressing 5-HT4(b) receptors. The potency for 5-HT did not change in clones expressing 5-HT7(a) receptors, even though 5-HT-stimulated AC activity approached asymptotic levels. This indicates that potency of 5-HT for stimulation of AC through the 5-HT7(a) receptor is independent of receptor-Gs stoichiometry and is consistent with a model where the 5-HT7(a) receptors are tightly associated with G protein, independent of agonist binding. This supports the existence of a complex between inactive receptor and G protein, as predicted by the cubic ternary complex model. In such a system, spare receptors do not lead to increased potency of an agonist with increased receptor density.     

Beta3 receptors mediate relaxation in stomach fundus whereas a fourth beta receptor mediates tachycardia in atria from transgenic beta3 receptor knockout mice

Pharmacological studies have revealed a non-beta1, beta2 or beta3 adrenergic receptor that mediates tachycardia in rat and human atria. The present studies utilized transgenic mice that lack the rodent beta3 receptor to explore, in a more definitive fashion, whether a non-beta1, beta2 or beta3 receptor can mediate atrial tachycardia. Insofar as the rat stomach fundus possesses a beta3 receptor mediating relaxation, we examined the stomach fundus from beta3 receptor knockout mice for the presence or absence of the beta3 relaxant receptor. Contractile responses to carbamylcholine were similar in potency and magnitude between mouse stomach fundus from wild type and beta3 receptor knockout animals. However, the classical beta3 receptor agonist CL316243, (10(-8)-10(-6)M) relaxed stomach fundus from wild type mice, but not from the beta3 receptor knockout animals. These data provide functional evidence for the absence of the beta3 receptor in beta3 receptor knockout animals and support the role of beta3 receptors mediating relaxation in mouse stomach fundus. Atria from mice lacking the beta3 receptor responded similarly (in potency and maximal increase in heart rate) to isoproterenol (10(-9)-10(-6)M) as atria from wild type mice. Furthermore, propranolol (3 x 10(-7) M) produced a dextral shift in the concentration response to isoproterenol in atria from both the beta3 receptor knockout and wild type mice with negative log K(B) values of 8.03 and 8.09, respectively. Thus, beta receptors mediating tachycardia to isoproterenol are intact and respond similarly in atria from both knockout and wild type mice. Furthermore, CGP12177, a prototypic 'atypical' beta receptor agonist produced tachycardia with a similar EC50 and maximal response in atria from both the wild type and beta3 receptor knockout mice. Cyanopindolol was a partial agonist relative to CGP12177 in both wild type and beta3 receptor knockout mice. Tachycardia to CGP12177 and cyanopindolol was not blocked by propranolol (3 x 10(-7) M) in atria from either group. These data provide definitive evidence that the receptor mediating tachycardia to CGP12177 and to cyanopindolol in atria from the transgenic beta3 receptor knockout mice is neither the beta1, beta2, nor beta3 adrenergic receptor.     

Agonist-like activity of antibodies directed against the second extracellular loop of the human cardiac serotonin 5-HT4(e) receptor in transfected COS-7 cells

We have previously reported that antipeptide antibodies directed against the second extracellular loop of the cardiac h5-HT4 receptor could block the activation of the L-type Ca channel in human atrial cardiomyocytes. In this paper we investigate the immunological and physiological activity of these antibodies, in a cell system expressing a larger amount of receptors than the atrial cells. The recombinant receptor was expressed at the surface of COS-7 cells under an active form (serotonin, EC50 = 1.81 x 10(-7) M), at a high level (375 +/- 25 fmol receptor/mg total protein) and was able to bind a specific ligand (GR113808) with a high affinity (Kd = 0.28 +/- 0.05 nM). In this system, the same anti-peptide antibodies used for the cardiac cells induced an "agonist-like" effect on the recombinant h5-HT4 receptor. These results are in line with those shown for others G-protein coupled receptors, as adrenoreceptors. In addition, this work showed that the effect of the antibodies is not only dependent on the epitopic region recognised but also on the molecular density and/or the cellular environment of the target receptors. Finally, our results support the hypothesis that the h5-HT4 receptor could be a new target for autoantibodies in patients with atrial arrhythmia.     

Polyclonal antibody effects on the human cardiac 5-HT4(e) receptors depend upon the expression system

The initial objective of this work was to examine the effects of an antibody (Anti-G21V) directed against the second extracellular loop of human heart 5-HT4 receptors expressed in Chinese hamster ovary (CHO) cells. The antibody anti-G21V had no effect upon either basal cAMP-or 5-HT-evoked increases in cAMP in CHO cells, whereas it had shown an agonist-like effect in COS-7 cells. Analysis of agonist fractions of h5-HT4(e) receptors in CHO and COS-7 cells revealed that equilibrium constant could underlie the different responses of the receptor toward the anti-G21V antibody. Therefore, different expression systems could give rise to functional differences in 5-HT4 receptor behavior.     

Enhancement of 5-hydroxytryptamine3A receptor function by phorbol 12-myristate, 13-acetate is mediated by protein kinase C and tyrosine kinase activity

The effects of phorbol 12-myristate, 13-acetate (PMA) on 5-hydroxytryptamine (5-HT)-evoked ion currents in the mouse 5-HT3A receptor were examined. Perfusion with PMA caused a concentration dependent potentiation of 5-HT mediated currents and increased both potency and efficacy of 5-HT at the 5-HT3A receptor expressed in Xenopus oocytes. Enhancement of receptor function was partially blocked by injection of oocytes with PKCI, the peptide inhibitor of protein kinase C (PKC). Mutation of all 12 intracellular serine and threonine residues to alanine was without effect on PMA-induced potentiation of 5-HT elicited currents. Mutation of tyrosine 458 in the 5-HT3A receptor lacking intracellular serines and threonines reduced the PMA-induced potentiation of 5-HT evoked currents by approximately 55%. In contrast, mutation of tyrosine 458 in the wild-type receptor did not alter PMA-induced enhancement. The tyrosine kinase inhibitor, lavendustin A, reduced the enhancement of 5-HT3A receptor mediated currents by PMA in the mutant 5-HTA3A receptor containing no intracellular serine or threonine residues, but not in the wild-type receptor. Thus, the role of intracellular serines and threonines is redundant with that of tyrosine, suggesting that these two components act through a similar pathway in response to PMA treatment.     

Phosphorylation of the 5-hydroxytryptamine3 (5-HT3) receptor expressed in HEK293 cells

The 5-hydroxytrptamine3 (5-HT3) receptor is a pentameric complex belonging to the family of ligand-gated ion channels. A variety of studies have suggested that phosphorylation regulates the rate of desensitisation and the size of amplitude of the receptor current. In this study we have examined the phosphorylation of the myc-tagged wild-type 5-HT3A receptor subunits from guinea-pig expressed in HEK293 cells (human embryonic kidney). Stably transfected cells were metabolically labelled with 32P-phosphoric acid. The results of immunoprecipitation and autoradiography demonstrate that both splicc variants of the 5-HT3A receptor subunit are phosphorylated in HEK293 cells. Site-specific mutagenesis revealed that phosphorylation occurs at serine 409, a potential target of protein kinase A. Thus the 5-HT3 receptor might be modulated by intracellular pathways, that allow variable 5-hydroxytryptamine action as responses to different extracellular stimuli.     

NR2B在硝酸甘油诱导的大鼠偏头痛中的表达变化所起作用的研究

目的：探讨在硝酸甘油（Nitroglycerin,NTG）诱导大鼠偏头痛中NMDA受体NR2B亚基的作用。方法：通过皮下注射硝酸甘油构建偏头痛大鼠模型,采用RT-PCR、免疫组织化学法检测三叉神经节中NR2B的表达变化。结果：偏头痛大鼠三叉神经节NR2B的mRNA和蛋白表达量较对照组明显升高（P〈0.05）。结论：NR2B通过神经传导可在偏头痛发病中起到重要作用。     

辛伐他汀对A549细胞阿米洛利敏感型钠离子通道α亚基表达的影响

目的;通过体外给药的方式观察辛伐他汀对人类肺泡上皮细胞（A549细胞代替）膜上阿米洛利敏感型钠离子通道α亚基（ENaC-α）表达的影响。方法：细胞株培养,分为空白组、2.5μM组、5μM组、10μM组,培养24小时,western blot检测ENaC-α膜蛋白表达,RT-PCR检测ENaC-αmRNA表达。结果：结果显示：2.5μM组ENaC-α膜蛋白与空白组无明显差别（P〉0.05）,5μM组高于空白组（P〈0.05）,10μM组明显高于空白组（P〈0.01）;2.5μM组ENaC-αmRNA与空白组无明显差别（P〉0.05）,5μM组表达增加（P〈0.05）,10μM组显著增加（P〈0.01）。结论：大剂量辛伐他汀增强A549细胞膜上ENaC-α膜蛋白及mRNA的表达。     

Scanning mutagenesis studies of the M1 muscarinic acetylcholine receptor

Following the solution of the structure of bovine rhodopsin by X-ray crystallography, it has been possible to build an improved homology model of the M(1) muscarinic acetylcholine receptor. This has been used to interpret the outcome of an extensive series of scanning and point mutagenesis studies on the transmembrane domain of the receptor. Potential intramolecular interactions enhancing the stability of the protein fold have been identified. The residues contributing to the binding site for the antagonist, N-methylscopolamine, and the agonist, acetylcholine have been mapped. The positively charged headgroups of these ligands appear to bind in a charge-stabilized aromatic cage formed by amino acid side chains in transmembrane (TM) helices 3, 6, and 7, while residues in TM 4 may participate in a peripheral docking site. Closure of the cage around the headgroup of acetylcholine may help to transduce binding energy into receptor activation, possibly disrupting a set of Van der Waals interactions between a set of residues underlying the binding site which help to constrain the receptor to the inactive state, in the absence of agonist. This may trigger the reorganization of a hydrogen bonding network between highly conserved residues in the core of the receptor, whose integrity is crucial for activation.     

Pharmacological analysis of the contractile role of M2 and M3 muscarinic receptors in smooth muscle

Muscarinic receptors expressed on smooth muscle cells are primarily of the M(2) and M(3) subtypes. The M(3) subtype triggers contraction through an interaction with G(q) proteins to stimulate phosphoinositide hydrolysis and mobilize Ca(2+). In contrast, activation of M(2) receptors modulates contraction by preventing relaxation or by potentiating M(3) receptor-mediated contractions, which enhances heterologous desensitization. These effects can be explained by the coupling of M(2) receptors to G(i) proteins that mediate an inhibition of adenylyl cyclase and calcium-activated potassium channels. The pharmacological antagonism of a response mediated through an interaction between M(2) and M(3) receptors has been shown to resemble the profile of the directly acting receptor (M(3)), primarily, and not that of the conditional receptor (M(2)). Evidence for a contractile role of the M(2) receptor has been obtained by inactivating its signaling pathway with pertussis toxin or by measuring contractile effects of muscarinic agonists after M(3) receptors have been covalently inactivated. Under these conditions, M(2) receptors have been shown to mediate an inhibition of the relaxant effects of agents, like isoproterenol, on the contractile effects of nonmuscarinic spasmogens. Muscarinic M(2) and M(3) receptor knockout mice are useful tools for exploring interactions between these receptors in smooth muscle.     

Messenger RNA localization and further characterisation of the putative tachykinin receptor NK4 (NK3B).

We have previously shown that a cloned receptor, highly homologous to the NK3 tachykinin peptide receptor, encodes a novel functional tachykinin receptor NK4. Examining sites of receptor mRNA expression by Northern blot we show that NK4 mRNA is expressed in numerous rat tissues, in contrast to the NK3 receptor which has been shown to have a distribution principally in nervous tissues. We have localised the NK4 receptor mRNA in rat brain and spinal cord using in situ hybridisation. NK4 receptor mRNA is widely expressed in neurons in the rat central nervous system, including cerebral cortex, hippocampus, hypothalamus and dorsal horn of the spinal cord. During peripheral inflammation of the hindpaw, NK4 mRNA shows complex patterns of regulation. We have also investigated some pharmacological properties of this receptor expressed ectopically in Xenopus oocytes. We show that the functional antagonism of dynorphin at the NK4 receptor is reversed by the non-specific opioid antagonist naloxone and that tachykinin-evoked responses at the NK4 receptor are inhibited by the non-peptide NK3 receptor antagonist SR142801 in a concentration dependent manner.     

Cellular signaling mechanisms for muscarinic acetylcholine receptors

Signaling pathways for muscarinic acetylcholine receptors (mAChRs) include several enzymes and ion channels. Recent studies have revealed the importance of various isoforms of both alpha and betagamma subunits of G proteins in initiation of signaling as well as the role of the small monomeric G protein, Rho, in the activation of phospholipase D. Modulation of adenylyl cyclase activity by mAChRs appears more diverse as the interaction of various receptor subtypes with the many isoforms of the enzyme are studied. Both alpha and beta subunits of G(i/o) may be involved. Some mAChR responses arise through release of nitric oxide from nitrergic nerves, including salivary gland secretion and hippocampal slow wave activity. mAChRs utilize a variety of intracellular pathways to activate various mitogen-activated protein kinases. The kinases are involved in cholinergic regulation of kidney epithelial function, catabolism of amyloid precursor protein, hippocampal long-term potentiation, activation of phospholipase A(2), and gene induction. mAChR activation can also stimulate or inhibit cellular growth and apoptosis, dependent on prior levels of cellular activity. Modulation of ion channels by mAChR agonists appears increasingly complex, based on recent studies. K(+) channels may be activated by M(2) and M(4) mAChR stimulation, although in the rat superior cervical ganglion topographical constraints appear to limit the effect to the M(2) mAChR. Another ganglionic K(+) current, the M current, is inhibited by M(1) mAChR activation, but in murine hippocampus inhibition involves another receptor subtype. R-type Ca(2+) channels are both facilitated and inhibited by M(1) and M(2) mAChRs; facilitation being more pronounced with activation of M(1) mAChRs and inhibition with M(2) mAChRs.     

基于遗传算法的卷积码快速译码

本文提出基于遗传算法(GA)的卷积码快速译码,进行格图上的单向(U-GA)和双向(B-GA)搜索译码.它利用遗传算法的群体多样性好、搜索空间宽广,具有全局优化能力,提高译码质量.通过模拟计算,分析了单向和双向的译码算法和群体规模M对误比特性能P_b的影响.模拟结果表明:在相同译码复杂度下、P_b=10^-6时,与MA算法(编码约束度K=19)相比,该译码算法约有0.5dB性能增益;与VA算法(K=7)相比,B-GA大约有1dB增益.     

High efficiency activation of L-type Ca2+ current by 5-HT in human atrial myocytes

In human atrial myocytes, serotonin rather than sympathetic, stimulation is more frequently associated with atrial fibrillation. So does the arrhythmogenic effect of serotonin result from the mechanism of action of the receptor or the context of its action upon cardiac myocytes? The capacity of agonists to produce cAMP followed the sequence 5-HT < Iso < Forskolin to increase ICaL with 5-HT = Iso = Forskolin. The simultaneous application of threshold concentrations of 5-HT and Iso maximally increased ICaL. We will show that the effect of 5-HT upon human atrial myocytes is an imbalance between low production of cAMP and maximal activation of ICaL.     

Functionalized DNA Nanomaterials Targeting Toll-Like Receptor 4 Prevent Bisphosphonate-Related Osteonecrosis of the Jaw via Regulating Mitochondrial Homeostasis in Macrophages

Imbalance of macrophage polarization characterized by an increase in the percentage of pro-inflammatory M1 macrophages and a decrease in anti-inflammatory M2 macrophages is considered a critical pathogenic mechanism of bisphosphonate-related osteonecrosis of the jaws (BRONJ). Because high levels of Toll-like receptor 4 (TLR4) mediates mitochondrial dyshomeostasis in Zoledronic Acid (ZA)-treated M1 macrophages, tetrahedral DNA nanomaterial (TDN)-modified with TLR4-siRNA on each vertex (TDN-TLR4-4siR) with excellent biocompatibility is synthesized. This novel TDN-TLR4-4siR nanomaterial reverses the polarization phenotype imbalance decreasing the percentage of M1 RAW264.7 macrophages. Mitochondrial dynamics analysis shows a shift from short rod-like ultrastructure to elongated shapes with more mitochondrial network continuity in ZA-primed M1 macrophages after treatment with TDN-TLR4-4siR, along with elevated expression of Mfn1 and Mfn2. TDN-TLR4-4siR further reduces intracellular ROS production and restored mitochondrial membrane potential. Furthermore, decreased sequestra formation and accelerated healing of the extraction wound are observed in the TDN-TLR4-4siR group, resulting in decreased incidence of rat BRONJ via reprogramming polarized macrophages. Consequently, this study establishes a novel strategy using TDN-TLR4-4siR nanomaterial to regulate mitochondrial homeostasis of polarized macrophages to prevent BRONJ.     

Dopamine and epinephrine, but not serotonin, downregulate dopamine sensitivity in cultured cortical and striatal astroglial cells

Biogenic amines are important in the regulation of neuronal functions and complex behavior in the brain. However, putative contributions of glial cells to physiological effects of aminergic transmitters and their pathophysiological implications are poorly understood. Astrocytes are known to respond to dopamine (DA) with calcium transients that can be blocked by the D1- and D2-receptor subtype specific antagonists SCH23390 and Sulpiride. We demonstrate here that DA-sensitivity of cortical and striatal astrocytes is changed by application of either DA or epinephrine (EP), but not serotonin (5-HT). Exposure of cortical and striatal astroglial cultures for less than 1h to DA (> or = 10 micromol/l) or EP (> or = 1 micromol/l) leads to a significant reduction of astroglial DA-sensitivity. Whereas the DA-mediated downregulation of astroglial DA-sensitivity can be reverted by SCH23390 (> or = 1 micromol/l), and Sulpiride (> or = 10 micromol/l), EP-mediated effects are insensitive to these antagonists. In contrast to receptor function, expression of D1- and D2-DA-receptors is not altered by either DA or EP in cortical and striatal astroglial cells as revealed by western blot analysis. Our results demonstrate that sensitivity of astroglial cells to DA is modulated by DA and EP, adding new evidence to a role of astrocytes as targets for physiological and pathological effects of aminergic transmitters.     

5-杂氮-2’-脱氧胞苷调控UCHL1基因表达对人前列腺癌PC-3细胞增殖及凋亡的影响

目的：探讨5-杂氮-2’-脱氧胞苷（5-Aza—CdR）对人前列腺癌细胞（PC-3）株增殖和凋亡的影响及其可能机制。方法以2．5、5．0、10．0kenol／L的5-Aza—CAR作用于PC-3细胞48h后,采用流式细胞术（FCM）检测细胞凋亡率;逆转录聚合酶链式反应（tiT—PcR）检测UCHL1 mRNA表达;甲基化测序聚合酶链反应（BsP）检测UCHLlCpG岛的甲基化状态;蛋白质印迹法（Western Blot）检测UCHL1蛋白的表达。结果：5-Aza—CAR对PC-3细胞生长有抑制作用;与对照组相比细胞凋亡率明显增高（P〈0．01）;5-Aza—CdR处理细胞后UCHL1的启动子甲基化水平明显降低（P〈0．01）;UCHL1 mRNA表达水平显著上调（P〈0．01）;UCHL1蛋白表达水平上升（P〈0．01）。结论：5-Aza—CAR能诱导前列腺癌PC-3细胞株凋亡的作用,其机制可能是5-Aza—CdR能逆转PC-3细胞UCHLl启动子CpG岛的异常甲基化,诱导mRNA转录和蛋白的表达。     

Evaluation of the critical electron dose on the contractile activity of hydrated muscle fibers in the film-sealed environmental cell.

By using the film-sealed environmental cell (EC) having a liquid-injection function, we observed a contraction reaction of hydrated myofibrils isolated from crab muscle under the transmission electron microscope. Our purpose in this work was to evaluate the critical electron dose at which the hydrated fibers lose the contractile activity. The decision of whether the fibers contracted was done by the existence of contraction band after a contraction reaction. From the observations, it was concluded that its critical dose was 2 x 10(-4) C/cm2 or 12 electrons/nm2 at a protein level.     

Reconstitution of human 5-hydroxytryptamine5A receptor--G protein coupling in E. coli and Sf9 cell membranes with membranes from Sf9 cells expressing mammalian G proteins.

The human 5-hydroxytryptamine5A (h5-ht5A) receptor was expressed in Escherichia coli (h5-ht5A-E. coli) to verify its pharmacological profile in the absence of G proteins. In addition, the ability of the h5-ht5A receptor to interact with mammalian Gi/o and Gs proteins was investigated by a new reconstitution approach. Agonists displayed lower affinities for h5-ht5A-E. coli than for stably transfected h5-ht5A-HEK 293 cells, due to the absence of G protein coupling in E. coli. Lysergic acid diethylamide behaved as a neutral antagonist, showing equal affinities for the G protein-coupled and the uncoupled receptor. To analyze the G protein coupling behavior of the h5-ht5A receptor, h5-ht5A-E. coli membranes or h5-ht5A-Sf9 insect cell membranes were fused by vortexing to membranes from baculovirus-infected Sf9 cells expressing mammalian G proteins. The ability of the h5-ht5A receptor to differentiate between Gi/Go/Gz and Gs proteins was explored by investigation of agonist binding affinities and agonist-induced stimulation of [35S]GTP gamma S binding. The h5-ht5A receptor failed to interact with Gz and Gs proteins and coupled equally well to Gj and Go proteins to form a complex with high affinity for agonists. Under the applied conditions, however, Gi proteins were found to be better activated than Go proteins in the [35S]GTP gamma S binding assay.