Heart 6-phosphofructo-2-kinase activation by insulin requires PKB (protein kinase B), but not SGK3 (serum- and glucocorticoid-induced protein kinase 3).
On the basis of transfection experiments using a dominant-negative approach, our previous studies suggested that PKB (protein kinase B) was not involved in heart PFK-2 (6-phosphofructo2-kinase) activation by insulin. Therefore we first tested whether SGK3 (serum- and glucocorticoid-induced protein kinase 3) might be involved in this effect. Treatment of recombinant heart PFK-2 with [γ-32P]ATP and SGK3 in vitro led to PFK-2 activation and phosphorylation at Ser466 and Ser483. However, in HEK-293T cells [HEK (human embryonic kidney)-293 cells expressing the large T-antigen of SV40 (simian virus 40)] co-transfected with SGK3 siRNA (small interfering RNA) and heart PFK-2, insulin-induced heart PFK-2 activation was unaffected. The involvement of PKB in heart PFK-2 activation by insulin was re-evaluated using different models: (i) hearts from transgenic mice with a muscle/heart-specific mutation in the PDK1 (phosphoinositide-dependent protein kinase 1)-substrate-docking site injected with insulin; (ii) hearts from PKBβ-deficient mice injected with insulin; (iii) freshly isolated rat cardiomyocytes and perfused hearts treated with the selective Akti-1/2 PKB inhibitor prior to insulin treatment; and (iv) HEK-293T cells co-transfected with heart PFK-2, and PKBα/β siRNA or PKBα siRNA, incubated with insulin. Together, the results indicated that SGK3 is not required for insulin-induced PFK-2 activation and that this effect is likely mediated by PKBα.
Mouton
Véronique
V
Université catholique de Louvain and de Duve Institute, 75 Avenue Hippocrate, Brussels, Belgium.
Toussaint
Louise
L
Vertommen
Didier
D
Gueuning
Marie-Agnès
MA
Maisin
Liliane
L
Havaux
Xavier
X
Sanchez-Canedo
Cossette
C
Bertrand
Luc
L
Dequiedt
Franck
F
Hemmings
Brian A
BA
Hue
Louis
L
Rider
Mark H
MH
D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation / Q000235:genetics; D009206:Myocardium / Q000166:cytology / Q000201:enzymology*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology; D009928:Organ Specificity / Q000187:drug effects; D025481:Phosphofructokinase-2 / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000378:metabolism*; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D051381:Rats; D017208:Rats, Wistar; D013379:Substrate Specificity / Q000187:drug effects; D000099184:Serum-Glucocorticoid Regulated Kinases
D007328:Insulin; D025481:Phosphofructokinase-2; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; C000631429:PDK1 protein, human; C000631433:Pdk1 protein, mouse; C000631434:Pdk1 protein, rat; C403243:SGK3 protein, human; D000099184:Serum-Glucocorticoid Regulated Kinases