Cytosolic Phosphoenolpyruvate carboxykinase is a key gluconeogenic enzyme which is expressed in a tissue specific manner in the liver, kidney and adipose tissue and is under hormonal control. The effect of glucocorticoids on expression of the gene coding for phosphoenolpyruvate carboxykinase in adipose tissue has been studied in vivo in rats and in vitro in adipose tissue organ culture and mouse 3T3 L1 adipocytes. Glucocorticoids, both in vivo and in vitro, repress the steady state level of phosphoenolpyruvate carboxykinase mRNA in the adipose tissue while increasing it in the kidney. The size of the mRNA and its 5′ end are identical in adipose tissue and kidney, thus the same promoter is used in all tissues. The inhibitory effect of glucocorticoids on phosphoenolpyruvate carboxykinase gene expression was located at the level of transcription. As glucocorticoids are known to stimulate transcription of phosphoenolpyruvate carboxykinase gene in the liver and kidney, the inhibitory effect on its transcription in adipose tissue suggests that tissue specific transcription factors may modulate the effect of glucocorticoids.
Bibliographical noteFunding Information:
We specially thank Dr. R. Miller for the gift of pGSRK-1 p1as;ni.l containing glutamine synthetase cDNA; to Dr. 0. Meyuhas for the clones containilg cDNA for souse ribosoml proteins and Dr. R.W. Hanson for the clones cmtsining PEPCK cDNA and genosic clone BH-1.2. We like to thank Drs. Yamnamots, R. Hanson and 0. Meyuhas for stinulating discussions and Ms R. Arad for the expertise in growing 3T3 L1 adipocytes. The research was supported by Grant 84-00167 from the United States - Israel Binational Foundation (BSF), Jerusalem, Israel and is part of the Ph.D thesis of Hovav Nechushtan to be submitted to the Hebrew University.