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cAMP Concentrations (camp + concentration)
Selected AbstractsA Phytochrome-like Protein AphC Triggers the cAMP Signaling Induced by Far-red Light in the Cyanobacterium Anabaena sp.PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2004Strain PCC7120 ABSTRACT In the filamentous, nitrogen-fixing cyanobacterium Anabaena sp. PCC7120, red light (630 nm) decreased, whereas far-red light (720 nm) increased cellular adenosine 3,,5,-cyclic monophosphate (cAMP) content. To find a red and far-red light photoreceptor that triggers the cAMP signal cascade, we disrupted 10 open reading frame having putative chromophore-binding GAF domains. The response of the cellluar cAMP concentration to red and far-red light in each open reading frame disruptant was determined. It was found that only the mutant of the gene all2699 failed to respond to far-red light. The open reading frame named as aphC encoded a protein with 920 amino acids including GAF domains similar to those involved in Cph2, a photoreceptor of Synechocystis sp. PCC6803. To determine which adenylate cyclase (AC) is responsible for far-red light signal, we disrupted all AC genes and found that CyaC was the candidate. The enzymatic activity of CyaC might be controlled by a far-red light photoreceptor through the phosphotransfer reaction. The site-specific mutant of the Asp59 residue of the receiver (R1) domain of CyaC lost its light-response capability. It was suggested that the far-red light signal was received by AphC and then transferred to the N-terminal response regulator domain of CyaC. Then its catalytic activity was stimulated, which increased the cellular cAMP concentration and drove the subsequent signal transduction cascade. [source] Cyclic Adenosine Monophosphate Regulation of Ion Transport in Porcine Vocal Fold Mucosae,THE LARYNGOSCOPE, Issue 8 2008Mahalakshmi Sivasankar PhD Abstract Objectives/Hypothesis: Cyclic adenosine monophosphate (cAMP) is an important biological molecule that regulates ion transport and inflammatory responses in epithelial tissue. The present study examined whether the adenylyl cyclase activator, forskolin, would increase cAMP concentration in porcine vocal fold mucosa and whether the effects of increased cAMP would be manifested as a functional increase in transepithelial ion transport. Additionally, changes in cAMP concentrations following exposure to an inflammatory mediator, tumor necrosis factor-, (TNF,) were investigated. Study Design: In vitro experimental design with matched treatment and control groups. Methods: Porcine vocal fold mucosae (N = 30) and tracheal mucosae (N = 20) were exposed to forskolin, TNF,, or vehicle (dimethyl sulfoxide) treatment. cAMP concentrations were determined with enzyme-linked immunosorbent assay. Ion transport was measured using electrophysiological techniques. Results: Thirty minute exposure to forskolin significantly increased cAMP concentration and ion transport in porcine vocal fold and tracheal mucosae. However, 30-minute and 2-hour exposure to TNF, did not significantly alter cAMP concentration. Conclusions: We demonstrate that forskolin-sensitive adenylyl cyclase is present in vocal fold mucosa, and further, that the product, cAMP increases vocal fold ion transport. The results presented here contribute to our understanding of the intracellular mechanisms underlying vocal fold ion transport. As ion transport is important for maintaining superficial vocal fold hydration, data demonstrating forskolin-stimulated ion transport in vocal fold mucosa suggest opportunities for developing pharmacological treatments that increase surface hydration. [source] Pharmacological characterization of a Bombyx mori ,-adrenergic-like octopamine receptor stably expressed in a mammalian cell lineARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2010Jia Huang Abstract Series of agonists and antagonists were examined for their actions on a Bombyx mori,-adrenergic-like octopamine receptor (OAR) stably expressed in HEK-293 cells. The rank order of potency of the agonists was clonidine>naphazoline>tolazoline in Ca2+ mobilization assays, and that of the antagonists was chlorpromazine>yohimbine. These findings suggest that the B. mori OAR is more closely related to the class-1 OAR in the intact tissue than to the other classes. N,-(4-Chloro- o -tolyl)- N -methylformamidine (DMCDM) and 2-(2,6-diethylphenylimino)imidazolidine (NC-5) elevated the intracellular calcium concentration ([Ca2+]i) with EC50s of 92.8,µM and 15.2,nM, respectively. DMCDM and NC-5 led to increases in intracellular cAMP concentration ([cAMP]i) with EC50s of 234,nM and 125,nM, respectively. The difference in DMCDM potencies between the cAMP and Ca2+ assays might be due to "functional selectivity." The Ca2+ and cAMP assay results for DMCDM suggest that the elevation of [cAMP]i, but not that of [Ca2+]i, might account for the insecticidal effect of formamidine insecticides. © 2009 Wiley Periodicals, Inc. [source] Regulated expression of HCN channels and cAMP levels shape the properties of the h current in developing rat hippocampusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2006Rainer Surges Abstract The hyperpolarization-activated current (Ih) contributes to intrinsic properties and network responses of neurons. Its biophysical properties depend on the expression profiles of the underlying hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels and the presence of cyclic AMP (cAMP) that potently and differentially modulates Ih conducted by HCN1, HCN2 and/or HCN4. Here, we studied the properties of Ih in hippocampal CA1 pyramidal cells, the developmental evolution of the HCN-subunit isoforms that contribute to this current, and their interplay with age-dependent free cAMP concentrations, using electrophysiological, molecular and biochemical methods. Ih amplitude increased progressively during the first four postnatal weeks, consistent with the observed overall increased expression of HCN channels. Activation kinetics of the current accelerated during this period, consonant with the quantitative reduction of mRNA and protein expression of the slow-kinetics HCN4 isoform and increased levels of HCN1. The sensitivity of Ih to cAMP, and the contribution of the slow component to the overall Ih, decreased with age. These are likely a result of the developmentally regulated transition of the complement of HCN channel isoforms from cAMP sensitive to relatively cAMP insensitive. Thus, although hippocampal cAMP concentrations increased over twofold during the developmental period studied, the coordinated changes in expression of three HCN channel isoforms resulted in reduced effects of this signalling molecule on neuronal h currents. [source] Regulation of human neutrophil-mediated cartilage proteoglycan degradation by phosphatidylinositol-3-kinaseIMMUNOLOGY, Issue 1 2001C. S. T. Hii Summary The ability of neutrophils to degrade cartilage proteoglycan suggests that the neutrophils that accumulate in the joints of rheumatoid arthritis patients are mediators of tissue damage. The regulatory mechanisms which are relevant to the proteoglycan-degrading activity of neutrophils are poorly understood. Since phosphatidylinositol 3-kinase (PI3-K), protein kinase C (PKC), the extracellular signal-regulated protein kinase (ERK)1/ERK2 and cyclic adenosine monophosphate (cAMP) have been reported to regulate neutrophil respiratory burst and/or degranulation, a role for these signalling molecules in regulating proteoglycan degradation was investigated. Preincubation of human neutrophils with GF109203X (an inhibitor of PKC), PD98059 (an inhibitor of MEK, the upstream regulator of ERK1/ERK2) or with forskolin or dibutyryl cAMP, failed to suppress proteoglycan degradation of opsonized bovine cartilage. In contrast, preincubation of neutrophils with wortmannin or LY294002, specific inhibitors of PI3-K, inhibited proteoglycan degradation. Incubation of neutrophils with cartilage resulted in the activation of PI3-K in neutrophils, consistent with a role for PI3-K in proteoglycan degradation. Activation of PI3-K and proteoglycan degradation was enhanced by tumour necrosis factor-,. Degradation caused by neutrophils from the synovial fluid of rheumatoid arthritis patients was also inhibited by wortmannin. These data demonstrate that the proteoglycan degradative activity of neutrophils required PI3-K but not PKC or the ERK1/ERK2/ERK5 cascades and was insensitive to increases in intracellular cAMP concentrations. [source] Band 4.1 proteins are expressed in the retina and interact with both isoforms of the metabotropic glutamate receptor type 8JOURNAL OF NEUROCHEMISTRY, Issue 6 2008Melanie Rose Abstract The function of the CNS depends on the correct regulation of neurotransmitter receptors by interacting proteins. Here, we screened a retinal cDNA library for proteins interacting with the intracellular C-terminus of the metabotropic glutamate receptor isoform 8a (mGluR8a). The band 4.1B protein binds to the C-termini of mGluR8a and mGluR8b, co-localizes with these glutamate receptors in transfected mammalian cells, facilitates their cell surface expression and inhibits the mGluR8 mediated reduction of intracellular cAMP concentrations. In contrast, no interaction with 4.1B was observed for other mGluRs tested. Amino acids encoded by exons 19 and 20 of 4.1B and a stretch of four basic amino acids present in the mGluR8 C-termini mediate the protein interaction. Besides binding to 4.1B, mGluR8 isoforms interact with 4.1G, 4.1N, and 4.1R. Because band 4.1 transcripts undergo extensive alternative splicing, we analyzed the splicing pattern of interacting regions and detected a 4.1B isoform expressed specifically in the retina. Within this tissue, mGluR8 and 4.1B, 4.1G, 4.1N, and 4.1R show a comparable distribution, being expressed in both synaptic layers and in somata of the ganglion cell layer. In summary, our studies identified band 4.1 proteins as new players for the mGluR8 mediated signal transduction. [source] Regulation of intracellular cyclic GMP levels in olfactory sensory neuronsJOURNAL OF NEUROCHEMISTRY, Issue 1 2005Cheil Moon Abstract Cyclic AMP is the primary second messenger mediating odorant signal transduction in mammals. A number of studies indicate that cyclic GMP is also involved in a variety of other olfactory signal transduction processes, including adaptation, neuronal development, and long-term cellular responses in the setting of odorant stimulation. However, the mechanisms that control the production and degradation of cGMP in olfactory sensory neurons (OSNs) remain unclear. Here, we investigate these mechanisms using primary cultures of OSNs. We demonstrate that odorants increase cGMP levels in intact OSNs in vitro. Different from the rapid and transient cAMP responses to odorants, the cGMP elevation is both delayed and sustained. Inhibition of soluble guanylyl cyclase and heme oxygenase blocks these odorant-induced cGMP increases, whereas inhibition of cGMP PDEs (phosphodiesterases) increases this response. cGMP PDE activity is increased by odorant stimulation, and is sensitive to both ambient calcium and cAMP concentrations. Calcium stimulates cGMP PDE activity, whereas cAMP and protein kinase A appears to inhibit it. These data demonstrate a mechanism by which odorant stimulation may regulate cGMP levels through the modulation of cAMP and calcium level in OSNs. Such interactions between odorants and second messenger systems may be important to the integration of immediate and long-term responses in the setting odorant stimulation. [source] In vitro characterization of HCN channel kinetics and frequency dependence in myocytes predicts biological pacemaker functionalityTHE JOURNAL OF PHYSIOLOGY, Issue 7 2009Xin Zhao The pacemaker current, mediated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, contributes to the initiation and regulation of cardiac rhythm. Previous experiments creating HCN-based biological pacemakers in vivo found that an engineered HCN2/HCN1 chimeric channel (HCN212) resulted in significantly faster rates than HCN2, interrupted by 1,5 s pauses. To elucidate the mechanisms underlying the differences in HCN212 and HCN2 in vivo functionality as biological pacemakers, we studied newborn rat ventricular myocytes over-expressing either HCN2 or HCN212 channels. The HCN2- and HCN212-over-expressing myocytes manifest similar voltage dependence, current density and sensitivity to saturating cAMP concentrations, but HCN212 has faster activation/deactivation kinetics. Compared with HCN2, myocytes expressing HCN212 exhibit a faster spontaneous rate and greater incidence of irregular rhythms (i.e. periods of rapid spontaneous rate followed by pauses). To explore these rhythm differences further, we imposed consecutive pacing and found that activation kinetics of the two channels are slower at faster pacing frequencies. As a result, time-dependent HCN current flowing during diastole decreases for both constructs during a train of stimuli at a rapid frequency, with the effect more pronounced for HCN2. In addition, the slower deactivation kinetics of HCN2 contributes to more pronounced instantaneous current at a slower frequency. As a result of the frequency dependence of both instantaneous and time-dependent current, HCN2 exhibits more robust negative feedback than HCN212, contributing to the maintenance of a stable pacing rhythm. These results illustrate the benefit of screening HCN constructs in spontaneously active myocyte cultures and may provide the basis for future optimization of HCN-based biological pacemakers. [source] Cyclic Adenosine Monophosphate Regulation of Ion Transport in Porcine Vocal Fold Mucosae,THE LARYNGOSCOPE, Issue 8 2008Mahalakshmi Sivasankar PhD Abstract Objectives/Hypothesis: Cyclic adenosine monophosphate (cAMP) is an important biological molecule that regulates ion transport and inflammatory responses in epithelial tissue. The present study examined whether the adenylyl cyclase activator, forskolin, would increase cAMP concentration in porcine vocal fold mucosa and whether the effects of increased cAMP would be manifested as a functional increase in transepithelial ion transport. Additionally, changes in cAMP concentrations following exposure to an inflammatory mediator, tumor necrosis factor-, (TNF,) were investigated. Study Design: In vitro experimental design with matched treatment and control groups. Methods: Porcine vocal fold mucosae (N = 30) and tracheal mucosae (N = 20) were exposed to forskolin, TNF,, or vehicle (dimethyl sulfoxide) treatment. cAMP concentrations were determined with enzyme-linked immunosorbent assay. Ion transport was measured using electrophysiological techniques. Results: Thirty minute exposure to forskolin significantly increased cAMP concentration and ion transport in porcine vocal fold and tracheal mucosae. However, 30-minute and 2-hour exposure to TNF, did not significantly alter cAMP concentration. Conclusions: We demonstrate that forskolin-sensitive adenylyl cyclase is present in vocal fold mucosa, and further, that the product, cAMP increases vocal fold ion transport. The results presented here contribute to our understanding of the intracellular mechanisms underlying vocal fold ion transport. As ion transport is important for maintaining superficial vocal fold hydration, data demonstrating forskolin-stimulated ion transport in vocal fold mucosa suggest opportunities for developing pharmacological treatments that increase surface hydration. [source] | |||||||||||||