Properties of protein kinase and adenylate cyclase‐deficient variants of a macrophage‐like cell line

Stable variants of the macrophage‐like cell line J774.2, defective in adenylate cyclase and protein kinase activities, were selected by cloning cells resistant to the growth‐inhibitory effect of cholera toxin and 8‐bromoadenosine 3′:5′ cyclic monophosphoric acid (8 Br‐cAMP), respectively. These variants were analyzed for their ability to respond to cyclic AMP‐mediated enhancement of phagocytosis and cyclic AMP‐mediated inhibition of plasminogen activator secretion and growth. The adenylate cyclase variants were unaffected by cholera toxin but were sensitive to 8 Br‐cAMP‐mediated inhibition of plasminogen activator secretion and growth. One of these variants exhibited a defect in phagocytosis that could be corrected by 8 Br‐cAMP. The protein kinase variants exhibited normal basal phagocytosis that could not be stimulated by either 8 Br‐cAMP or cholera toxin; they were also insensitive to cyclic AMP‐mediated inhibition of plasminogen activator secretion and growth. The studies demonstrate that the three effects of cyclic AMP in J774.2–inhibition of growth and plasminogen activator secretion, and enhancement of basal Fc‐mediated phagocytosis–are mediated by a cyclic AMP‐dependent protein kinase. The results support the usefulness of variants in cyclic nucleotide metabolism in understanding the regulation of differentiated cell function by cyclic AMP.