Cyclic AMP Accumulation Induces a Rapid Desensitization of the Cyclic AMP‐Dependent Protein Kinase in Mouse Striatal Neurons

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Abstract
: Striatal neurons from the mouse brain embryo grown in primary culture express high levels of cyclic AMP (cAMP)‐dependent protein kinase (PK A) activity. To study the modulation of PKA in intact neurons, a rapid method based on Zn2+‐protein precipitation was developed. This strategy allowed analysis of the stimulation of PKA under conditions of intracellular cAMP concentration increases. Whereas increases up to 1 μM lead to an activation, large and sustained accumulations of cAMP result in a loss of the enzyme activity. With 8‐bromo‐cAMP (8‐Br‐cAMP) at 100 μM, the PKA refractoriness occurs within 2 min. It is rapidly reversible because incubation of treated neurons in fresh medium leads to a complete recovery of PKA activity within 30 min. The decrease in assayable PKA does not involve an activation of phosphatases because the histone dephosphorylation rate is not affected by 8‐Br‐cAMP treatment Finally, not only 8‐Br‐cAMP‐but also forskolin‐and vasoactive intestinal peptide‐induced increases in intracellular cAMP concentration can lead to the PKA desensitization. Altogether, these data unravel a new mechanism of PKA regulation.