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An Assay for Measuring the Activity of Escherichia coli Inducible Lysine Decarboxyase
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An Assay for Measuring the Activity of Escherichia coli Inducible Lysine Decarboxyase

Published on: December 19, 2010

Cyclic AMP-dependent protein kinase mediates a cyclic AMP-stimulated decrease in ornithine and S-adenosylmethionine

P A Insel, J Fenno

    Proceedings of the National Academy of Sciences of the United States of America
    |February 1, 1978
    PubMed

    Insights

    N6,O2'-dibutyryl cyclic AMP (Bt2cAMP) reduces key polyamine synthesis enzymes in S49 cells, mediated by protein kinase. This mirrors cell cycle arrest, suggesting cell passage is crucial for enzyme activity.

    Area of Science:

    • Cell Biology
    • Biochemistry
    • Molecular Biology

    Background:

    • Polyamines are essential for cell growth and proliferation.
    • Ornithine decarboxylase and S-adenosylmethionine decarboxylase are key enzymes in polyamine synthesis.
    • Cyclic AMP (cAMP) signaling pathways regulate various cellular processes.

    Purpose of the Study:

    • To investigate the effect of N6,O2 -dibutyryl cyclic AMP (Bt2cAMP) on polyamine synthesis enzymes in S49 lymphoma cells.
    • To elucidate the role of cAMP-dependent protein kinase in regulating these enzymes.
    • To correlate enzyme activity changes with cell cycle progression.

    Main Methods:

    • Incubation of S49 cells with varying doses of Bt2cAMP.
    • Assay of ornithine decarboxylase and S-adenosylmethionine decarboxylase activities.
    • Studies using S49 mutant clones with altered protein kinase.
    • Analysis of cell cycle arrest and release dynamics.

    Main Results:

    • Bt2cAMP dose-dependently decreased ornithine decarboxylase and S-adenosylmethionine decarboxylase activities after a 3-hr delay.
    • cAMP-dependent protein kinase was identified as the mediator of this decrease.
    • The enzyme activity decrease paralleled cAMP-stimulated G1 cell cycle arrest.
    • Ornithine decarboxylase activity decreased faster than Bt2cAMP-induced arrest and increased faster than G1 exit.

    Conclusions:

    • cAMP signaling, via protein kinase, downregulates key polyamine synthesis enzymes in S49 cells.
    • These effects are linked to cell cycle arrest, specifically in the G1 phase.
    • Cell cycle passage appears necessary for maintaining the activity of ornithine and S-adenosylmethionine decarboxylases, contrasting with other cell types.

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