GLUCOSE REGULATES THE PROMOTER ACTIVITY OF ALDOLASE-A AND PYRUVATE-KINASE M-2 VIA DEPHOSPHORYLATION OF SP1

Proliferating cells and tumour cells maintain a high glycolytic rate e ven under aerobic conditions, FTO2B cells, a rat hepatoma cell line, s how high activities of glycolytic enzymes, Within a culture period of 48 h the cell number increases 5-fold, Replacement of glucose by pyruv ate in the culture medium lowers glycolytic enzyme activity and preven ts proliferation, Transfection assays revealed that glucose deprivatio n dramatically decreases the transcriptional activities of the Sp1-dep endent aldolase and pyruvate kinase promoters leading to reduced repor ter gene expression, Sp1 binding activity is also inhibited by ocadaic acid, an inhibitor of protein phosphatase 1. Western blot analyses wi th nuclear extracts from FTO2B cells cultured in the presence or absen ce of glucose revealed differences in the phosphorylation state of Sp1 , From these results we conclude that glucose increases the amount of the dephosphorylated form of Sp1 which has a higher DNA binding activi ty, As a consequence gene expression of the glycolytic enzymes is incr eased which is a prerequisite for cell proliferation. (C) 1997 Federat ion of European Biochemical Societies.