Regulation of Adenosine 3′:5′-Cyclic Monophosphate Phosphodiesterase Activity in Fibroblasts by Intracellular Concentrations of Cyclic Adenosine Monophosphate
AUTOR(ES)
D'Armiento, Massimo
RESUMO
Cyclic AMP-phosphodiesterase is present in various mouse fibroblasts. Contact-inhibited 3T3 cells contain two forms of the enzyme, one with a Km of 2.5 μM and the second with a Km of 71 μM. As 3T3 cells grow to confluency and cAMP concentrations rise, the activity of the first enzyme increases, whereas that of the second is unchanged. A line of SV40-transformed 3T3 cells with low cAMP concentration also has low levels of the cAMP-phosphodiesterase with a Km of 2.5 μM. Treatment of 3T3 and SV40-transformed 3T3 cells with dibutyryl cAMP and theophylline increases cAMP-phosphodiesterase accumulation. This accumulation is blocked by cycloheximide and actinomycin D. The newly formed enzyme resembles the higher affinity enzyme present in unstimulated cells, since it has a Km of 1.2-2.0 μM, and is stimulated by snake venom. In L cells in which cAMP concentrations are elevated by treatment with prostaglandin E1, cAMP phosphodiesterase also accumulates. We conclude that intracellular concentrations of cAMP regulate the synthesis of cAMP-phosphodiesterase, and that cAMP functions as an inducer of the enzyme.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=426480Documentos Relacionados
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