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Calmodulin modulates the cyclic AMP level in Xenopus oocyte

O Mulner, J Tso, D Huchon

    Cell Differentiation
    |April 1, 1983
    PubMed

    Insights

    Progesterone reduces cyclic adenosine monophosphate (cAMP) levels in Xenopus oocytes through two pathways: one involving calcium-calmodulin and another independent of it. This suggests dual mechanisms regulate oocyte cAMP.

    Area of Science:

    • Reproductive biology
    • Cellular signaling
    • Endocrinology

    Background:

    • Cyclic adenosine monophosphate (cAMP) is a crucial second messenger in cellular processes.
    • Hormonal regulation of oocyte maturation involves complex signaling pathways.
    • Cholera toxin and IBMX are commonly used to elevate intracellular cAMP levels for experimental manipulation.

    Purpose of the Study:

    • To investigate the mechanisms by which progesterone affects cAMP levels in Xenopus oocytes.
    • To determine the role of calcium-calmodulin in progesterone-mediated cAMP regulation.
    • To elucidate the signaling pathways involved in controlling oocyte cAMP concentration.

    Main Methods:

    • Xenopus oocytes were pretreated with cholera toxin and IBMX to increase cAMP.
    • Progesterone was administered externally or via microinjection.
    • Calcium ionophore A 23187 and calcium-calmodulin were microinjected.
    • Inhibitors of calcium-calmodulin (anticalmodulin antibodies, fluphenazine) were used.

    Main Results:

    • Progesterone consistently decreased cAMP levels in Xenopus oocytes, regardless of pretreatment.
    • Calcium-calmodulin activation (via ionophore or direct injection) decreased cAMP.
    • Inhibition of calcium-calmodulin increased cAMP levels.
    • Progesterone's cAMP-lowering effect was observed even when calcium-calmodulin was inhibited.

    Conclusions:

    • Oocyte cAMP levels are negatively regulated by at least two parallel pathways.
    • One pathway involves the calcium-calmodulin complex, likely inhibiting adenylate cyclase.
    • Progesterone exerts a distinct, parallel inhibitory effect on cAMP that does not require calcium-calmodulin activation.

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