Insulin inhibits glucocorticoid-stimulated L-type 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase gene expression by activation of the c-Jun N-terminal kinase pathway.
The hepatic isoform of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PF2K/Fru-2,6-BPase) is transcriptionally stimulated by glucocorticoids, whereas insulin blocks this stimulatory effect. Although this inhibitory effect has been extensively reported, nothing is known about the signalling pathway responsible. We have used well-characterized inhibitors for proteins involved in different signalling cascades to assess the involvement of these pathways on the transcriptional regulation of glucocorticoid-stimulated PF2K/Fru-2,6-BPase by insulin. Our results demonstrate that the phosphoinositide 3-kinase, p70/p85 ribosomal S6 kinase, extracellular signal-regulated protein kinase (ERK)1/2 and p38 mitogen-activated protein (MAP) kinase pathways are not involved in the inhibitory effect of insulin on glucocorticoid-stimulated PF2K/Fru-2,6-BPase. To evaluate the implication of the MAP kinase/ERK kinase (MEK)-4-stress-activated protein kinase-c-Jun-N-terminal protein kinase ('JNK-SAPK') pathway we overexpressed the N-terminal JNK-binding domain of the JNK-interacting protein 1 ('JIP-1'), demonstrating that activation of JNK is necessary for the insulin inhibitory effect. Moreover, overexpression of MEK kinase 1 and JNK-haemagglutinin resulted in the inhibition of the glucocorticoid-stimulated PF2K/Fru-2,6-BPase. These results provide clear and specific evidence for the role of JNK in the insulin inhibition of glucocorticoid-stimulated PF2K/Fru-2,6-BPase gene expression. In addition, we performed experiments with a mutant of the glucocorticoid receptor in which the JNK phosphorylation target Ser-246 had been mutated to Ala. Our results demonstrate that the phosphorylation of the glucocorticoid receptor on Ser-246 is not responsible for the JNK repression of glucocorticoid-stimulated PF2K/Fru-2,6-BPase gene expression.
De Los Pinos E
Departament de Bioquímica i Biologia Molecular, Div. IV, Facultat de Farmàcia, Universitat de Barcelona, Av. Diagonal 643, E08028 Barcelona, Catalunya, Spain.
Fernández De Mattos S
Joaquin
M
M
Tauler
A
A
D000818:Animals; D002867:Chromones / Q000494:pharmacology; D003907:Dexamethasone / Q000037:antagonists & inhibitors / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006597:Fructose-Bisphosphatase / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D007328:Insulin / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009025:Morpholines / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D010732:Phosphofructokinase-1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D025481:Phosphofructokinase-2; D010957:Plasmids; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured
D002867:Chromones; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007328:Insulin; D009025:Morpholines; D009097:Multienzyme Complexes; D012333:RNA, Messenger; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D003907:Dexamethasone; D025481:Phosphofructokinase-2; D010732:Phosphofructokinase-1; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D006597:Fructose-Bisphosphatase; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D020123:Sirolimus