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Cyclic AMP Production (cyclic + amp_production)
Selected AbstractsA family of octapamine receptors that specifically induce cyclic AMP production or Ca2+ release in Drosophila melanogasterJOURNAL OF NEUROCHEMISTRY, Issue 2 2005Sabine Balfanz Abstract In invertebrates, the biogenic-amine octopamine is an important physiological regulator. It controls and modulates neuronal development, circadian rhythm, locomotion, ,fight or flight' responses, as well as learning and memory. Octopamine mediates its effects by activation of different GTP-binding protein (G protein)-coupled receptor types, which induce either cAMP production or Ca2+ release. Here we describe the functional characterization of two genes from Drosophila melanogaster that encode three octopamine receptors. The first gene (Dmoa1) codes for two polypeptides that are generated by alternative splicing. When heterologously expressed, both receptors cause oscillatory increases of the intracellular Ca2+ concentration in response to applying nanomolar concentrations of octopamine. The second gene (Dmoa2) codes for a receptor that specifically activates adenylate cyclase and causes a rise of intracellular cAMP with an EC50 of ,3 × 10,8 m octopamine. Tyramine, the precursor of octopamine biosynthesis, activates all three receptors at ,,100-fold higher concentrations, whereas dopamine and serotonin are non-effective. Developmental expression of Dmoa genes was assessed by RT,PCR. Overlapping but not identical expression patterns were observed for the individual transcripts. The genes characterized in this report encode unique receptors that display signature properties of native octopamine receptors. [source] Regulation of Tyrosine Hydroxylase Activity and Phosphorylation at Ser19 and Ser40 via Activation of Glutamate NMDA Receptors in Rat StriatumJOURNAL OF NEUROCHEMISTRY, Issue 6 2000Niklas Lindgren Abstract: The activity of tyrosine hydroxylase, the rate-limiting enzyme in the biosynthesis of dopamine, is stimulated by phosphorylation. In this study, we examined the effects of activation of NMDA receptors on the state of phosphorylation and activity of tyrosine hydroxylase in rat striatal slices. NMDA produced a time-and concentration-dependent increase in the levels of phospho-Ser19 -tyrosine hydroxylase in nigrostriatal nerve terminals. This increase was not associated with any changes in the basal activity of tyrosine hydroxylase, measured as DOPA accumulation. Forskolin, an activator of adenylyl cyclase, stimulated tyrosine hydroxylase phosphorylation at Ser40 and caused a significant increase in DOPA accumulation. NMDA reduced forskolin-mediated increases in both Ser40 phosphorylation and DOPA accumulation. In addition, NMDA reduced the increase in phospho-Ser40 -tyrosine hydroxylase produced by okadaic acid, an inhibitor of protein phosphatase 1 and 2A, but not by a cyclic AMP analogue, 8-bromo-cyclic AMP. These results indicate that, in the striatum, glutamate decreases tyrosine hydroxylase phosphorylation at Ser40 via activation of NMDA receptors by reducing cyclic AMP production. They also provide a mechanism for the demonstrated ability of NMDA to decrease tyrosine hydroxylase activity and dopamine synthesis. [source] Inhibition of adenylyl cyclase by neuronal P2Y receptorsBRITISH JOURNAL OF PHARMACOLOGY, Issue 3 2002Ursula Unterberger P2Y receptors inhibiting adenylyl cyclase have been found in blood platelets, glioma cells, and endothelial cells. In platelets and glioma cells, these receptors were identified as P2Y12. Here, we have used PC12 cells to search for adenylyl cyclase inhibiting P2Y receptors in a neuronal cellular environment. ADP and ATP (0.1 , 100 ,M) left basal cyclic AMP accumulation unaltered, but reduced cyclic AMP synthesis stimulated by activation of endogenous A2A or recombinant ,2 receptors. Forskolin-dependent cyclic AMP production was reduced by 1 ,M and enhanced by 10 , 100 ,M ADP; this latter effect was turned into an inhibition when A2A receptors were blocked. The nucleotide inhibition of cyclic AMP synthesis was not altered when P2X receptors were blocked, but abolished by pertussis toxin. The rank order of agonist potencies for the reduction of cyclic AMP was (IC50 values): 2-methylthio-ADP (0.12 nM)=2-methylthio-ATP (0.13 nM)>ADP,S (71 nM)>ATP (164 nM)=ADP (244 nM). The inhibition by ADP was not antagonized by suramin, pyridoxal-phosphate-6-azophenyl-2,,4,-disulphonic acid, or adenosine-3,-phosphate-5,-phosphate, but attenuated by reactive blue 2, ATP,S, and 2-methylthio-AMP. RT , PCR demonstrated the expression of P2Y2, P2Y4, P2Y6, and P2Y12, but not P2Y1, receptors in PC12 cells. In Northern blots, only P2Y2 and P2Y12 were detectable. Differentiation with NGF did not alter these hybridization signals and left the nucleotide inhibition of adenylyl cyclase unchanged. We conclude that P2Y12 receptors are expressed in neuronal cells and inhibit adenylyl cyclase activity. British Journal of Pharmacology (2002) 135, 673,684; doi:10.1038/sj.bjp.0704514 [source] Evidence for cocaine and methylecgonidine stimulation of M2 muscarinic receptors in cultured human embryonic lung cellsBRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2001Yinke Yang Muscarinic cholinoceptor stimulation leads to an increase in guanylyl cyclase activity and to a decrease in adenylyl cyclase activity. This study examined the effects of cocaine and methylecgonidine (MEG) on muscarinic receptors by measurement of cyclic GMP and cyclic AMP content in cultured human embryonic lung (HEL299) cells which specifically express M2 muscarinic receptors. A concentration-dependent increase in cyclic GMP production was observed in HEL299 cells incubated with carbachol, cocaine, or MEG for 24 h. The increase in cyclic GMP content was 3.6 fold for 1 ,M carbachol (P<0.01), 3.1 fold for 1 ,M cocaine (P<0.01), and 7.8 fold for 1 ,M MEG (P<0.001), respectively. This increase in cyclic GMP content was significantly attenuated or abolished by the muscarinic receptor antagonist atropine or the M2 blocker methoctramine. In contrast, cocaine, MEG, and carbachol produced a significant inhibition of cyclic AMP production in HEL299 cells. Compared to the control, HEL299 cells treated with 1 ,M cocaine decreased cyclic AMP production by 30%. MEG and carbachol at 1 ,M decreased cyclic AMP production by 37 and 38%, respectively. Atropine or methoctramine at 1 or 10 ,M significantly attenuated or abolished the cocaine-induced decrease in cyclic AMP production. However, the antagonists alone had neither an effect on cyclic GMP nor cyclic AMP production. Pretreatment of HEL299 cells with pertussis toxin prevented the cocaine-induced reduction of cyclic AMP production. Western blot analysis showed that HEL299 cells specifically express M2 muscarinic receptors without detectable M1 and M3. Incubation of HEL299 cells with cocaine, carbachol, and atropine did not alter the expression of M2 protein levels. However, the inducible isoform of nitric oxide synthase (iNOS) was induced in the presence of cocaine or carbachol and this induction was significantly attenuated after addition of atropine or methoctramine. The present data show that cocaine and MEG significantly affect cyclic GMP and cyclic AMP production in cultured HEL299 cells. Our results also show that these effects result from the drug-induced stimulation of M2 muscarinic receptors accompanied with no alterations of receptor expression. However, the induction of iNOS by cocaine may result in the increase in cyclic GMP production. British Journal of Pharmacology (2001) 132, 451,460; doi:10.1038/sj.bjp.0703819 [source] A comparison of agonist-specific coupling of cloned human ,2 -adrenoceptor subtypesBRITISH JOURNAL OF PHARMACOLOGY, Issue 5 2000Jane E Rudling The agonist-specific coupling properties of the three cloned human ,2 -adrenoceptor subtypes have been compared, when expressed at similar levels in Chinese hamster ovary (CHO) cell lines, using noradrenaline and (±)- meta -octopamine as agonists. Noradrenaline can couple the receptor to both the inhibition and stimulation of forskolin-stimulated cyclic AMP production in all three receptor subtypes, with the relative strength of the coupling to the pathways varying for each of the receptor subtypes. meta -Octopamine selectively couples the ,2A -adrenoceptor only to the inhibition of forskolin-stimulated cyclic AMP production. However, meta -octopamine couples the ,2B - and ,2C -adrenoceptors to both the inhibition and stimulation of forskolin-stimulated cyclic AMP production. The relative potency of meta -octopamine to noradrenaline varies between the different ,2 -adrenoceptor subtypes. The effects of meta -octopamine are around two orders of magnitude less potent than those of noradrenaline on both the ,2A - and ,2B -adrenoceptor subtypes. In contrast, in the case of the ,2C -adrenoceptor, meta -octopamine is only one order of magnitude less potent than noradrenaline in the stimulation of forskolin-stimulated cyclic AMP production and, in addition, is equipotent with noradrenaline in the inhibition of forskolin-stimulated cyclic AMP production and has an increased maximal response. This raises the possibility that meta -octopamine may have physiologically important actions via ,2C -adrenoceptors in vivo. The results show that the modulation of cyclic AMP production occurs in both a subtype- and agonist-specific manner for ,2A -adrenoceptors and in a subtype specific manner for ,2B - and ,2C -adrenoceptors. British Journal of Pharmacology (2000) 131, 933,941; doi:10.1038/sj.bjp.0703644 [source] ORIGINAL ARTICLE: Monoclonal autoantibodies to the TSH receptor, one with stimulating activity and one with blocking activity, obtained from the same blood sampleCLINICAL ENDOCRINOLOGY, Issue 3 2010Michele Evans Summary Objective, Patients who appear to have both stimulating and blocking TSHR autoantibodies in their sera have been described, but the two activities have not been separated and analysed. We now describe the isolation and detailed characterization of a blocking type TSHR monoclonal autoantibody and a stimulating type TSHR monoclonal autoantibody from a single sample of peripheral blood lymphocytes. Design, patients and measurements, Two heterohybridoma cell lines secreting TSHR autoantibodies were isolated using standard techniques from the lymphocytes of a patient with hypothyroidism and high levels of TSHR autoantibodies (160 units/l by inhibition of TSH binding). The ability of the two new monoclonal antibodies (MAbs; K1-18 and K1-70) to bind to the TSHR and compete with TSH or TSHR antibody binding was analysed. Furthermore, the effects of K1-18 and K1-70 on cyclic AMP production in Chinese hamster ovary cells (CHO) cells expressing the TSHR were investigated. Results, One MAb (K1-18) was a strong stimulator of cyclic AMP production in TSHR-transfected CHO cells and the other (K1-70) blocked stimulation of the TSHR by TSH, K1-18, other thyroid-stimulating MAbs and patient serum stimulating type TSHR autoantibodies. Both K1-18 (IgG1 kappa) and K1-70 (IgG1 lambda) bound to the TSHR with high affinity (0·7 × 1010 l/mol and 4 × 1010 l/mol, respectively), and this binding was inhibited by unlabelled K1-18 and K1-70, other thyroid-stimulating MAbs and patient serum TSHR autoantibodies with stimulating or blocking activities. V region gene analysis indicated that K1-18 and K1-70 heavy chains used the same V region germline gene but different D and J germline genes as well as having different light chains. Consequently, the two antibodies have evolved separately from different B cell clones. Conclusions, This study provides proof that a patient can produce a mixture of blocking and stimulating TSHR autoantibodies at the same time. [source] | ||||||||||