PPAR-GAMMA-2 REGULATES ADIPOSE EXPRESSION OF THE PHOSPHOENOLPYRUVATE CARBOXYKINASE GENE

Phosphoenolpyruvate carboxykinase (PEPCK) is expressed at high levels in liver, kidney, acid adipose tissue. This enzyme catalyzes the rate- limiting step in hepatic and renal gluconeogenesis and adipose glycero neogenesis. The regulatory factors important for adipose expression of the PEPCK gene are not well defined. Previous studies with transgenic mice established that the region between bp -2086 and -888 is require d for expression in adipose tissue but not for expression in liver or kidney tissue. We show here that a DNA fragment containing this region can function as an enhancer and direct differentiation-dependent expr ession of a chloramphenicol acetyltransferase gene from a heterologous promoter in cultured 3T3-F442A preadipocytes and adipocytes. We furth er demonstrate that the adipocyte-specific transcription factor PPAR g amma 2, previously identified as a regulater of the adipocyte P2 enhan cer, binds in a heterodimeric complex with RXR alpha to the PEPCK 5'-f lanking region at two sites, termed PCK1 (bp -451 to -439) and PCK2 (b p -999 to -987). Forced expression of PPAR gamma 2 and RXR alpha activ ates the PEPCK enhancer in non-adipose cells. This activation is poten tiated by peroxisome proliferators and fatty acids but not by 9-cis re tinoic acid. Mutation of the PPAR gamma 2 binding site (PCK2) abolishe s both the activity of the enhancer in adipocytes and its ability to b e activated by PPAR gamma 2 and RXR alpha. These results establish a r ole for PPAR gamma 2 in the adipose expression of the PEPCK gene and s uggest that this factor functions as a coordinate regulator of multipl e adipocyte-specific genes.