![]() ![]() These results also demonstrate the independent control of morphological change and enzyme synthesis during adipose differentiation. We conclude that, in addition to its activation of lipolysis, cAMP reduces specifically mRNA accumulation for lipogenic enzymes. Translation in vitro of mRNA isolated from cells treated with the agents promoting cAMP accumulation indicates that the levels of functional mRNA for lipogenic enzymes are reduced. Protein kinase A phosphorylates the OH of a serine residue on phosphorylase kinase. The effects of the agents on the synthesis of lipogenic enzymes are not dependent on lipolysis, since they take place to the same degree in cells not permitted to accumulate triglyceride. The increased level of 3,5-cyclic-AMP in the cytosol activates protein kinase A (for details see p. In contrast to their effects on lipogenic enzyme synthesis, these agents do not affect morphological changes or the synthesis of several other proteins, of which some increase and others (such as actin) decrease during the differentiation. The extent of reduction depends on the agent used and differs for the three enzymes fatty acid synthetase is most sensitive and its synthesis can be suppressed completely. Agents that increase cAMP content (Dibutyryl cAMP, theophylline, and isoproterenol) are known to induce lipolysis in fat cells but the same agents are shown here to reduce the synthesis of the lipogenic enzymes during adipose differentiation. During the adipose differentiation of 3T3-F442A cells, there is an increase in the synthesis of numerous proteins, including the lipogenic enzymes glycerophosphate dehydrogenase, fatty acid synthetase and malic enzyme. ![]()
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