Abstract
The induction of ornithine decarboxylase was studied following the stimulation of human peripheral blood lymphocytes with concanavalin A (ConA) (10 µg/ml). Following treatment with ConA, ornithine decarboxylase activity increased 4-5-fold between 6 and 12 hr of incubation and reached a peak level 10-12-fold above control (unstimulated) values by 48 hr. Increases in incorporation of [3H]uridine into acid-insoluble material followed a similar time course after the addition of ConA to lymphocytes. The rate of incorporation of [3H]thymidine into acid-insoluble material was maximal at 72 hr. The degree of activation of soluble cyclic 3',5'-AMP-dependent protein kinase(s) was determined at various times following ConA stimulation. Between 1 and 2 hr after mitogen administration, the cyclic AMP-dependent protein kinase activity ratio increased markedly and was 0.23 unit above control values by 4 hr. The activity ratio decreased between 4 and 8 hr and returned to higher values after incubation with the mitogen for 12, 24, and 48 hr. Separation of the free catalytic subunit from type I and type II protein kinase holoenzyme isozymes via C6-aminoalkyl agarose chromatography revealed that only type I protein kinase was activated 4 hr following incubation of lymphocytes with a mitogenic concentration of ConA (10 µg/ml). The addition of dibutyryl cyclic AMP at the same time as ConA (10 µg/ml) resulted in nearly total activation of both type I and type II protein kinases at 4 hr but was inhibitory to the later induction of ornithine decarboxylase and to increased synthesis of RNA and DNA. A high concentration of ConA (100 µg/ml), which also activated both isozyme forms of the kinase at 4 hr, produced only a small increase in ornithine decarboxylase activity and RNA synthesis at later times and no elevation in DNA synthesis. The data suggest that while the early activation of type I cyclic AMP-dependent protein kinase may mediate in a positive manner the induction of ornithine decarboxylase and the mitogenic response of lymphocytes to ConA, concomitant activation of type II protein kinase may inhibit this process.
- Copyright © 1978 by Academic Press, Inc.
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