Treatment of primary rat epididymal adipocytes or 3T3-L1 adipocytes with various agents which increase cAMP led to the phosphorylation of eukaryotic translation elongation factor-2 (eEF-2). The increase in eEF-2 phosphorylation was a consequence of the activation of eEF-2 kinase (eEF-2K), which is a Ca2+/calmodulin-dependent kinase. eEF-2K was shown to be essentially inactive at less than 0.1 µM free Ca2+ when measured in cell-free extracts. Treatment of adipocytes with isoproterenol induced Ca2+-independent eEF-2K activity, and an 8–10-fold activation of eEF-2K was observed at Ca2+ concentrations of less than 0.1 µM. Increased cAMP in 3T3-L1 adipocytes led to the inhibition of total protein synthesis and decreased the rate of polypeptide-chain elongation. We also show that the phosphorylation of eEF-2 and the activity of eEF-2K are insulin-regulated in adipocytes. These results demonstrate a novel mechanism for the control of protein synthesis by hormones which act by increasing cytoplasmic cAMP.
Regulation of protein-synthesis elongation-factor-2 kinase by cAMP in adipocytes
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Tricia A. DIGGLE, Nicholas T. REDPATH, Kate J. HEESOM, Richard M. DENTON; Regulation of protein-synthesis elongation-factor-2 kinase by cAMP in adipocytes. Biochem J 15 December 1998; 336 (3): 525–529. doi: https://doi.org/10.1042/bj3360525
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