cAMP and adenylate cyclase activity in Streptomyces granaticolor

Abstract Intracellular and extracellular cyclic adenosine 3',5'-monophosphate (cAMP) levels were determined during the growth of Streptomyces granaticolor . The intracellular level of cAMP represents not more than 10% of the total amount. cAMP synthesis varies in cultures growing on different carbon sources. The activity of adenylate cyclase in intact cells is strictly dependent on the presence of a metabolizable carbon source.     

Role of cGMP- and cAMP-Dependent Systems in the Effects of Nitric Oxide on Transmitter Release and Potassium Currents in the Frog Neuromuscular Junction

We studied the molecular mechanisms responsible for nitric oxide (NO)-evoked modulation of the synaptic function in the frog neuromuscular junction using inhibitors of adenylate and guanylate cyclases and analogs of cyclic nucleotides. It was shown that application of an exogenous donor of NO, sodium nitroprusside, decreased transmitter release and increased the amplitude of voltage-dependent potassium current of the nerve endings. Our results indicate that NO regulates transmitter release and potassium current in the frog neuromuscular junction both via cAMP- and cGMP-dependent mechanisms.     

植物病原真菌环磷酸腺苷信号通路研究进展

环磷酸腺苷(cyclic adenosine monophosphate, cAMP)是广泛存在于真核生物中的第二信使,其由腺苷酸环化酶(adenylate cyclase, AC)合成后,通过结合蛋白激酶A (protein kinase A, PKA)调控下游蛋白活性,从而参与植物病原真菌的生长发育、致病性(或致病力)、细胞壁完整性、环境胁迫响应及有性/无性生殖等方面的调控。本文介绍了植物病原真菌cAMP信号通路的信号转导及其与细胞中其他信号通路之间的交叉调控的相关研究进展,同时阐述了cAMP信号通路在植物病原真菌侵染过程中的重要作用。为今后以cAMP信号通路相关基因或蛋白作为靶点筛选抑制植物病原真菌的药物,以及利用cAMP信号通路对植物病原真菌生长发育及致病等相关调控机制进行病害防控提供了新的策略和思路。     

Regulatory mechanisms of fatty acid isomers on adenylate cyclase activity from Ceratitis capitata brain

Summary The regulatory properties of saturated and unsaturated fatty acids on membrane-bound preparations of adenylate cyclase from Ceratitis capitata brains have been investigated. Saturated long-chain fatty acids do not exhibit any significant modification of the enzyme activity of the enzyme preparations but the presence of one, two or three double bonds in the 18C chain provokes an inhibitory effect. Binding of oleate and linoleate to the membrane enzyme preparation is non-specific and simply stochiometric in the range of concentrations examined. Studies of cis and trans isomers of the double-bond isomers, 18:1 (n–9) and 18:1(n–11), reveal the higher inhibitory effect of the cis isomers on membrane-bound adenylate cyclase of the insect brain. The inhibitory effect of cis-vaccenate in the basal conditions of the enzyme assay is identical to the effects obtained in the presence of GTP and octopamine.Insect membrane preparations were labeled with 1,6-diphenyl-1,3,5-hexatriene as fluorescent probe and treated with cis and trans 18:1(n–9) and 18:1 (n–11). The fluorescence polarization parameter was measured, from which the microviscosity of the preparations was calculated; microviscosity of the membranes treated with both cis isomers decreased in a clear extent whereas it is not influenced by the trans isomers.     

Inactivation of enteroviruses, rotaviruses and bacteriophages by peracetic acid in a municipal sewage effluent

Abstract Cells of B. subtilis are able to synthesize cAMP in response to oxygen limitation. Several methods were used to characterize cAMP in cell extracts. Using [³H]adenosine, cAMP synthesis could also be detected under in vivo conditions. Furthermore, activities of phosphodiesterase and adenylate cyclase were measured in extracts of B. subtilis cells and in membrane fractions. We suggest that in B. subtilis cAMP is synthesized only under special physiological conditions.     

Adenylate cyclase-mediated modulation of interaction between excitatory and inhibitory synaptic influences on smooth muscles

We found that nonadrenergic inhibitory synaptic potentials (ISP) induced by intramural stimulation in atropine-treated smooth muscles of the guinea-pig large intestine demonstrated no changes upon the influence of an activator of adenylate cyclase, forskolin. This indicates that cAMP-dependent pathways are not involved in the generation of ISP. However, in these muscles with no atropine pretreatment ISP were suppressed by forskolin; intramural stimulation evoked in these smooth muscle cells M-cholinergic excitatory synaptic potentials (ESP) instead of ISP. An increase in the intracellular cAMP concentration due to application of its membrane-penetrating form, dibutyryl-cAMP, did not mimic the above-described effect of forskolin. Hence, it can be supposed that the effect of forskolin on inhibitory synaptic transmission in the atropine-untreated smooth muscles is not related to changes in the intracellular cAMP level; this effect is determined by other mechanisms. The above differences between the effects of forskolin on ISP in the atropine-treated and atropine-untreated smooth muscle strips indicate that the interaction of intracellular signal pathways (probably, through protein G_q/11), which is observed with activation of adenylate cyclase, occurs under conditions of simultaneous activation of M cholinoreceptors and purinoreceptors. The pattern of adenylate cyclase-mediated modulation of inhibitory effects of purinergic neurons on smooth muscles does not allow us to rule out the possibility of involvement of interstitial cells of Cajal as a relay link providing this synaptic effect. Transmission of excitation from cholinergic nerve terminals to smooth muscles is realized without the participation of the interstitial cells of Cajal.Neirofiziologiya/Neurophysiology, Vol. 36, Nos. 5/6, pp. 438–445, September–December, 2004.This revised version was published online in April 2005 with a corrected cover date and copyright year.     

Intracellular cAMP in Dictyostelium discoideum: Characterization of an aggregation-deficient mutant with elevated cAMP pools

Forty aggregation-deficient mutants of Dictyostelium discoideum were screened for changes in intracellular cAMP during the first 10 hr of starvation. The pools in 39 of the mutants remained low and relatively static during this period. However, amoebae of one mutant, strain HC151, exhibited significantly elevated levels of intracellular cAMP during vegetative growth and for several hours after starvation. A more detailed analysis of this mutant indicated that the elevated cAMP pools in these cells are a consequence of the premature appearance and partial activation of an adenylate cyclase. The mutation(s) altering adenylate cyclase regulation in this strain appears to map in linkage group IV. Complementation tests between strain HC151 and another mutant, HH201, which has recently been shown to produce an adenylate cyclase activity precociously [1], indicated that the mutations affecting adenylate cyclase activity in these strains map at different loci. Although both of these mutations behave recessively in heterozygous diploids with respect to gross development, an examination of early cAMP metabolism and terminal spore differentiation in these diploids suggest that these mutations are at least partially expressed during some stage(s) of the developmental cycle.     

腺苷酸环化酶3缺失对小鼠主要嗅觉表皮组织内DNA甲基化的影响

腺苷酸环化酶3 (adenylate cyclaseⅢ,AC3)是嗅觉系统中的重要成分,AC3缺失后小鼠的主要嗅觉表皮组织(main olfactory epidermal,MOE)随年龄增长逐渐变薄,MOE内基因表达谱发生改变. DNA甲基化在动物发育、基因表达调控中具有重要作用.为了探讨AC3缺失后小鼠MOE内基因启动子甲基化水平的改变以及对基因表达的影响,本文采用DNA甲基化免疫共沉淀芯片(methylated DNA immunoprecipitation chip,MeDIP-chip)筛选AC3缺失小鼠MOE内启动子区甲基化差异表达基因,利用甲基化特异PCR (methylation-specific PCR,MSP)、实时荧光定量PCR (qRT-PCR)进一步检测部分甲基化差异基因的DNA甲基化水平改变和表达差异.结果表明,AC3缺失小鼠中有1 978个基因启动子的甲基化水平发生了改变,占总探针数的9%,其中727个基因启动子甲基化水平升高,1 251个甲基化水平降低.功能分析表明,这些启动子甲基化发生改变的基因主要涉及的功能分别与嗅觉受体、神经发育、cAMP信号通路、ATP结合、钙离子调控、乙酰化修饰、转录因子等相关. MSP检测表明,嗅觉受体基因Olfr1153、Olfr231、Olfr378、Olfr651、Olfr691启动子区的甲基化水平升高,Cngb1、Pde4a和Olfr1394基因启动子区的甲基化水平降低. qRT-PCR结果显示,基因Cngb1、Hcn4、Olfm1、Olfr1394、Olfr1153、Olfr231、Olfr378、Olfr691的表达水平显著下降,而Pde4a和Olfr651基因的表达水平显著升高.总之,AC3缺失后MOE内嗅觉受体基因、神经发育相关基因、cAMP信号通路等相关基因启动子甲基化水平发生显著改变,影响核苷酸切除修复、DNA复制、错配修复等信号通路的传导,从而综合调控小鼠MOE内的基因表达数量和水平.     

Influence of lithium on dopamine-stimulated adenylate cyclase activity in rat brain

Dopamine-stimulated adenylate cyclase activity from various rat brain areas was inhibited $\text{in vitro}$ by lithium. The inhibition was dose-dependent and non-competitive. In lithium-treated rats no changes in enzyme activity could be demonstrated.     

垂体腺苷酸环化酶激活多肽对鲤鱼脑垂体细胞内cAMP和Ca^2＋的影响

采用环腺苷酸 (cAMP)放射免疫测定法和活细胞内Ca2 荧光探针Indo 1,研究绵羊垂体腺苷酸环化酶激活多肽 (oPACAP)对原代培养的鲤鱼脑垂体细胞内cAMP和游离Ca2 ([Ca2 ]i)的影响 ,以期探讨PACAP调节脑垂体生长激素 (GH)分泌的机制受体后。oPACAP 38和oPACAP 2 7以剂量依存方式促进脑垂体细胞内cAMP释放和合成。oPACAP 38和oPACAP 2 7也能升高脑垂体细胞内 [Ca2 ]i 水平 ,该作用会因用EGTA消竭细胞外Ca2 ([Ca2 ]e)而迅速消失 ;L型电位敏感性Ca2 通道 (VSCC)阻断剂硝苯吡啶可抑制oPACAP 38诱导的 [Ca2 ]i 水平的升高 ,而当用硝苯吡啶预处理脑垂体细胞 ,oPACAP 38诱导 [Ca2 ]i 水平升高作用完全被抑制。可见 ,PACAP刺激鲤鱼脑垂体GH分泌机制包括依赖于cAMP和依赖于通过L型VSCC内流的 [Ca2 ]e 的机制。     

Molecular characterization of an adenylate cyclase gene of the cyanobacterium Spirulina platensis

A cyaA gene, encoding an adenylate cyclase, was isolated from a filamentous cyanobacterium, Spirulina platensis, by functional complementation of a cya mutant of Escherichia coli, defective in adenylate cyclase activity. The predicted gene product of cyaA contains a signal peptide-like domain, a putative sensor domain similar to the gene product of vsrA of Pseudomonas solanacearum, a putative membrane-spanning domain and an adenylate cyclase-like catalytic domain. Two other positive clones that complemented the E. coli mutant were isolated from the same cyanobacterium, suggesting that several cya genes are functioning in S. platensis.     

Effects of selected vasoactive substances on adenylate cyclase activity in brain,isolated brain microvessels,and primary cultures of brain microvessel endothelial cells

The specific activity of adenylate cyclase was assayed in homogenates of gray matter, freshly isolated and primary cultured microvessel endothelial cells from bovine cerebral cortex. Specific activities for the tissues were 14.6±2.1, 15.6±2.7, and 8.4±1.5 pmol cAMP/mg protein/min±SD for gray matter, cultured microvessels, and freshly isolated microvessels, respectively. Adenylate cyclase associated with gray matter and cultured microvessels was sensitive to histamine and selected catecholamines. Perhaps due to metabolic deficiencies, adenylate cyclase of freshly isolated microvessels exhibited little or no response to either the catecholamines or histamine. Angiotensin II stimulated adenylate cyclase of both freshly isolated and cultured microvessels but had no effect on gray matter. Bradykinin did not stimulate cAMP generation in any of the tissues. Overall results support the role of cAMP in regulating brain microvessel functions and suggest that primary cultures of brain microvessels may be useful in examining cAMP-mediated biochemical pathways at the blood-brain barrier.     

Cell activation during regeneration of planarians

Planarians are a good subject for studies of cell differentiation. Each multicellular organism is maintained by continuous production, differentiation and ageing of cellular elements. Each cell has a specific position defined by specific regional boundaries.After amputating a part of the body this positional information changes, involving, probably, the first range of cellular activation, the activation of membrane receptors. At the same time in an injured organism the level of neurohormones, which can be now coupled with activated receptors, increases. In the opinion of many authors neurohormones act on the regenerative cells through the medium of adenylate cyclase. This enzyme converts ATP to cAMP and by means of this cyclic nucleotide the second range of cellular activation is initiated i.e. changes of activation of cAMP dependent protein kinases.The sequence of these processes plays the principal role in the ensuing cell differentiation.