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  • 1
    Digitale Medien
    Digitale Medien
    Ca2+/Calmodulin Distinguishes Between Guanyl-5′-yl-Imidodiphosphate-and Opiate-Mediated Inhibition of Rat Striatal Adenylate Cyclase (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 49 (1987), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: The inhibition of adenylate cyclase from rat striatal plasma membranes by guanyl-5′-yl-imidodiphos-phate [Gpp(NH)p] and morphine was compared to determine whether Gpp(NH)p-mediated inhibition accurately reflected hormone-mediated inhibition in this system. Inhibition of adenylate cyclase activity by Gpp(NH)p and morphine was examined with respect to temperature, divalent cation concentration, and the presence of Ca2+/calmodulin (Ca2+/CaM). Gpp(NH)p-mediated inhibition was dependent on the presence of Ca2+/CaM at 24°C; the inhibition was independent of Ca2+/CaM at 18°C; and inhibition could not be detected in the presence, or absence, of Ca2+/ CaM at 30°C. In contrast, naloxone-reversible, morphine-induced inhibition of adenylate cyclase was independent of both temperature and the presence of Ca2+/CaM. Mg2+dose-response curves also reinforced the differences in the Ca2+/CaM requirement for Gpp(NH)p-and morphine-induced inhibition. Because Gpp(NH)p-mediated inhibition was independent of Ca2+/CaM at low basal activities (i.e., 18°C, or below 1 mM Mg2+) and dependent on the presence of Ca2+/CaM at higher basal activities (24°C, or above 1 mM Mg2+), the inhibitory effects of Gpp(NH)p were examined at 1 mM Mg2+ in the presence of 100 nM forskolin. Under these conditions, both Gpp(NH)p-and morphine-induced inhibition of adenylate cyclase were independent of Ca2+/CaM. The results demonstrate that the requirement for Ca2+/CaM to observe Gpp(NH)p-mediated inhibition depends on the basal activity of adenylate cyclase, whereas hormone-mediated inhibition is Ca2+/CaM independent under all conditions. Further, this study shows that, under certain conditions, Gpp(NH)p-mediated inhibition of adenylate cyclase does not mimic the inhibition of adenylate cyclase produced by a complete interaction between the inhibitory hormone receptor, the guanine nucleotide-regulatory component that mediates inhibition, and the catalytic unit of the adenylate cyclase complex in striatal plasma membranes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1987.tb10025.x
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  • 2
    Digitale Medien
    Digitale Medien
    Inhibition of Cyclic AMP Accumulation in Intact NCB-20 Cells as a Direct Result of Elevation of Cytosolic Ca2+ (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 59 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Earlier studies established that adenylyl cyclase in NCB-20 cell plasma membranes is inhibited by concentrations of Ca2+ that are achieved in intact cells. The present studies were undertaken to prove that agents such as bradykinin and ATP, which elevate the cytosolic Ca2+ concentration ([Ca2+]i) from internal stores in NCB-20 cells, could inhibit cyclic AMP (cAMP) accumulation as a result of their mobilization of [Ca2+]i and not by other mechanisms. Both bradykinin and ATP transiently inhibited [3H]cAMP accumulation in parallel with their transient mobilization of [Ca2+]i. The [Ca2+]i rise stimulated by bradykinin could be blocked by treatment with thapsigargin; this thapsigargin treatment precluded the inhibition of cAMP accumulation mediated by bradykinin (and ATP). A rapid rise in [Ca2+]i, as elicited by bradykinin, rather than the slow rise evoked by thapsigargin was required for inhibition of [3H]cAMP accumulation. Desensitization of protein kinase C did not modify the inhibitory action of bradykinin on [3H]cAMP. Effects of Ca2+ on phosphodiesterase were also excluded in the present studies. The accumulated data are consistent with the hypothesis that hormonal mobilization of [Ca2+]i leads directly to the inhibition of cAMP accumulation in these cells and presumably in other cells that express the Ca2+-inhibitable form of adenylyl cyclase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb10992.x
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  • 3
    Digitale Medien
    Digitale Medien
    Interaction of the Inhibitory GTP Regulatory Component with Soluble Cerebral Cortical Adenylate Cyclase (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 46 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Functional interaction of the inhibitory GTP regulatory component (Ni) with the adenylate cyclase catalytic subunit has not previously been demonstrated after detergent solubilization. The present report describes a sodium cholate-solubilized preparation of rat cerebral cortical membrane adenylate cyclase that retains guanine nucleotide-mediated inhibition of activity. Methods of membrane preparation, cholate extraction, and assay conditions were manipulated such that guanosine-5′-(β-γ-imido)triphosphate [Gpp(NH)p] inhibited basal activity 40–60%. The rank order of potency among various GTP analogs was similar in cholate extracts and in membranes: guanosine-5′-0-(3-thiotriphosphate) 〉 Gpp(NH)p 〉 GTP. Inclusion of 0.1 mM EGTA reduced basal activity 70–90% and abolished Gpp(NH)p inhibition of basal activity in both membranes and cholate extracts. Forskolin-stimulated activity was also inhibited by Gpp(NH)p. Treatment of either membranes or cholate extracts with N-ethylmaleimide abolished Gpp(NH)p inhibition. Gel filtration of the cholate extract over a Sepharose 6B column in 0.1% Lubrol PX partially resolved the adenylate cyclase components. However, Gpp(NH)p inhibitin of basal activity (60% of the control) was maintained in select column fractions. Sucrose gradient centrifugation totally resolved the catalytic subunit from both functional Ni and stimulatory GTP regulatory component (Ns) activities. The sedimentation of functional Ni activity was detected by assaying the ability of sucrose gradient fractions to confer Gpp(NH)p inhibition of the resolved catalytic activity. Labeling of gradient or column fractions with pertussis toxin and [32P]NAD revealed that both the 39,000- and 41,000-dalton substrates comigrated with the functional Ni activity. These results demonstrate the feasibility of reconstituting Ni inhibition with resolved catalytic activity directly in solution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb01769.x
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  • 4
    Digitale Medien
    Digitale Medien
    Manipulation of Intracellular Calcium in NCB-20 Cells (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 59 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: A number of lines of evidence indicate that the Ca2+ and cyclic AMP signalling systems interact in NCB-20 cells. However, to date, the regulation of [Ca2+]i homeosta-sis has not been studied in this cell line. The present study aimed to clarify our understanding of [Ca2+]i homeostasis in these cells and to evaluate tools that manipulate [Ca2+]i, independently of protein kinase C effects. Bradykinin, by a B2-receptor, elevated [Ca2+]i by a pertussis-toxin-insensitive mechanism. The BK-stimulated [Ca2+]i rise originated from intracellular sources, without a contribution from Ca2+ entry mechanisms. The effect of BK was precluded by pre-treatment with thapsigargin and ionomycin—compounds that elevated [Ca2+]i independent of phospholipase C activation. Both compounds, however, exerted effects in addition to stimulating release of Ca2+ from BK-sensitive stores; the BK-sensitive Ca2+ pool was a subset of the thapsigargin-sensitive pool; ionomycin strongly stimulates Ca2+ entry. Activation of protein kinases A and C attenuated the duration of the BK-induced rise in [Ca2+]i, without affecting the peak [Ca2+]i, suggesting interference with the BK response at a step downstream of the activation of phospholipase C. Application of these approaches should enhance the delineation of the consequences of Ca2+ mobilization on cyclic AMP accumulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb08890.x
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  • 5
    Digitale Medien
    Digitale Medien
    Opiate Receptor-Mediated Inhibition of Adenylate Cyclase in Rat Striatal Plasma Membranes (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 38 (1982), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Plasma membranes from rat striatum contain adenylate cyclase activity that is subject to dual regulation by GTP. Low concentrations (up to 30 nM) of the nucleotide increase activity whereas higher concentrations evoke a steady decline in activity; such behavior characterizes dually regulated adenylate cyclase systems. The opiates, morphine sulfate and D-Ala-Met-enkephalin, produce naloxone-reversible inhibition of the enzyme that is dependent on “inhibitory concentrations” of GTP (above 50 nM). In the absence of GTP no inhibition is observed. Sodium ions decrease the inhibition of activity promoted by GTP alone, but amplify the degree of inhibition seen in the presence of the opiates and GTP. The potencies of the opiates in mediating these effects mirror their affinities for 8 opiate receptors in striatum. It is suggested that this action of the opiates may represent their primary action in striatum.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1982.tb05365.x
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  • 6
    Digitale Medien
    Digitale Medien
    Role of Calmodulin in the Effect of Guanyl Nucleotides on Rat Hippocampal Adenylate Cyclase: Involvement of Adenosine and Opiates (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 41 (1983), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: The adenylate cyclase activity of rat hippocampal plasma membranes can be stimulated by vaso-active intestinal polypeptide (VIP). Low concentrations (10−9 to 10−7M) of 5′-guanylyl-imido diphosphate (GppNHp) evoke a transient inhibition of the enzyme, which is followed by stimulation with increasing GppNHp concentrations (10−6 to 10−4M). Inclusion of ethyleneglycol - bis - (β - aminoethylether) - N,N′ - tetraacetic acid (EGTA) during incubation abolishes the GppNHp inhibition while preserving GppNHp activation. The stimulation induced by GppNHp is amplified by VIP, but the inhibition is unaffected. Adenosine analogs and opiates are inhibitory ligands in the presence of GTP, and their effects can be reversed by the appropiate receptor antagonists, 3-isobutyl-1-methylxanthine and naloxone. Treatment of membranes with trypsin abolishes the GppNHp-induced inhibition without affecting the GppNHp stimulation. The inhibition induced by GppNHp is also abolished by EGTA treatment followed by washing, which coincides wtih a reduction in the adenosine- and opiate-mediated, GTP-dependent inhibition. The GppNHp inhibition can be restored in EGTA-treated but not in trypsin-treated membranes by addition of calcium-calmodulin but not by Ca2+ or Mg2+. Calcium-calmodulindepleted membranes lack calcium stimulation as well as GppNHp-induced inhibition, whereas untreated membranes and calcium-calmodulin-depleted membranes plus exogenous calcium-calmodulin showed calcium stimulation and GppNHp inhibition. These results suggest that calmodulin is involved in both Ca2+ stimulation and guanine nucleotide-mediated inhibition of rat hippocampal adenylate cyclase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1983.tb04818.x
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  • 7
    Digitale Medien
    Digitale Medien
    Adenylyl Cyclase mRNA Expression does not Reflect the Predominant Ca2+/Calmodulin-Stimulated Activity in the Hypothalamus (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neuroendocrinology 6 (1994), S. 0 
    Details
    ISSN: 1365-2826
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Only three (Types I, II, V) of the six currently-described subtypes of adenylyl cyclase are prominently expressed in the rat brain. These species are differently sensitive to Ca2+, βγ subunits of G-proteins and protein kinase C. A knowledge of the susceptibility of the cAMP-signalling system in particular brain regions to these diverse modes of regulation can shed light on the mechanism of action of the neurotransmitters that modify neuronal activity in such regions. Cyclic AMP is extensively involved in the physiological functions of the hypothalamus. We have used in situ hybridization histochemistry with synthetic oligonucleotides to examine the expression in the rat hypothalamus of the three major brain subtypes of adenylyl cyclase-Ca2+/calmodulin-stimulable (Type I), Ca2+-insensitive (Type II) and Ca2+ -inhibitable (Type V). The hypothalamus expresses high levels only of Type II mRNA, particularly in the supraoptic and paraventricular nuclei. Curiously, the strong expression of the Ca2+-insensitive Type II mRNA and the lack of expression of the major brain specific Type I mRNA does not correlate with the adenylyl cyclase activity, which is largely Ca2+/calmodulin stimulable in plasma membranes prepared from the hypothalamus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2826.1994.tb00633.x
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  • 8
    Digitale Medien
    Digitale Medien
    Spontaneous Intracellular Calcium Oscillations and Gsα Subunit Expression are Inversely Correlated with Secretory Granule Content in Pituitary Cells (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neuroendocrinology 4 (1992), S. 0 
    Details
    ISSN: 1365-2826
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Cells of the pituitary tumour cell line GH4C1 were exposed to epidermal growth factor, estradiol and insulin for 5 days, a treatment which resulted in 1) increased prolactin storage in secretory granules, 2) the loss of spontaneous [Ca2+]1 oscillations, and 3) a selective reduction of the protein Gsα, seen in immunoblots, cholera toxin labelling, and vasoactive intestinal peptide stimulation of adenylyl cyclase. In contrast, the glucocorticoid dexamethasone, which increases the expression of Gsα, partially restored spontaneous [Ca2+]1 oscillations and decreased prolactin storage. It is concluded that Gsα levels in tumoral cells result in spontaneous electrical activity which may empty prolactin stores by the continuous activation of exocytosis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2826.1992.tb00195.x
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  • 9
    Digitale Medien
    Digitale Medien
    ADP is a potent inhibitor of human platelet plasma membrane adenylate cyclase (1979)
    [s.l.] : Nature Publishing Group
    Nature 282 (1979), S. 517-518 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] In these studies membranes were prepared essentially as described by Barber and Jamieson10. The procedure involves lysis of glycerol-loaded freshly drawn washed human platelets, followed by sucrose gradient centrifugation of the particulate fraction and collection of the plasma membrane-enriched ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/282517a0
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  • 10
    Digitale Medien
    Digitale Medien
    Adenylyl cyclases and the interaction between calcium and cAMP signalling (1995)
    [s.l.] : Nature Publishing Group
    Nature 374 (1995), S. 421-424 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Adenylyl cyclase is the prototypical second messenger generator. Nearly all of the eight cloned adenylyl cyclases are regulated by one or other arm of the phospholipase C pathway. Functional and ultrastructural investigations have shown that adenylyl cyclases are intimately associated with sites of ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/374421a0
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