Expression of the phosphoenolpyruvate carboxykinase gene and its insulin regulation during differentiation of preadipose cell lines.

The adipose conversion of Ob1771 and 3T3-F442A preadipose cells is accompanied by the expression of the phosphoenolpyruvate carboxykinase (PEPCK) gene. The PEPCK mRNA is absent from growing, undifferentiated Ob1771 and 3T3-F442A cells as well as from non-differentiating 3T3-C2 cells. It is present in differentiated Ob1771 and 3T3-F442A cells as well as in liver, kidney and white adipose tissue from mouse. Transcriptional run-off measurements in nuclei isolated from undifferentiated and differentiated Ob1771 and 3T3-F442A cells reveal that the PEPCK gene transcription is activated during differentiation. Studies of the time course of changes indicate that the emergence of PEPCK mRNA takes place in parallel to mRNA encoding for a 28 kDa protein (28 K mRNA) but later than that encoding for glycerol-3-phosphate dehydrogenase (GPDH mRNA). Insulin leads to an increase in the content of PEPCK and GPDH mRNAs with half-maximally effective concentrations of 0.5 and 5 nM for GPDH mRNA and PEPCK mRNA, respectively. Thus, in contrast to rat hepatoma cells, insulin exerts in adipose cells a positive regulation on the expression of the PEPCK gene.