GSK-3beta regulation in skeletal muscles by adrenaline and insulin: evidence that PKA and PKB regulate different pools of GSK-3.
We have recently shown that while adrenaline alone has no effect on the activation of Protein Kinase B (PKB) in rat soleus muscle, it greatly potentiates the effects of insulin (Brennesvik et al., Cellular Signalling 17: 1551-1559, 2005). In the current study we went on to investigate whether this was paralleled by a similar effect on GSK-3, which is a major PKB target. Surprisingly adrenaline alone increased phosphorylation of GSK-3beta Ser9 and GSK-3alpha Ser21 and adrenaline's effects were additive with those of insulin but did not synergistically potentiate insulin action. Dibutyryl-cAMP (5 mM) and the PKA specific cAMP analogue N6-Benzoyl-cAMP (2 mM) increased GSK-3beta Ser9 phosphorylation, whereas the Epac specific cAMP analogue 8-(4-chlorophenylthio)-2'-O-methyl-cAMP (1 mM) did not. Wortmannin (PI 3-kinase inhibitor; 1 microM) blocked insulin-stimulated GSK-3 phosphorylation completely, but adrenaline increased GSK-3beta Ser9 phosphorylation in the presence of wortmannin. The PKA inhibitor H89 (50 microM) reduced adrenaline-stimulated GSK-3beta Ser9 phosphorylation but did not influence the effects of insulin. Insulin-stimulated GSK-3 Ser9 phosphorylation was paralleled by decreased glycogen synthase phosphorylation at the sites phosphorylated by GSK-3 as expected. However, adrenaline-stimulated GSK-3 Ser9 phosphorylation was paralleled by increased glycogen synthase phosphorylation indicating this pool of GSK-3 may not be directly involved in phosphorylation of glycogen synthase. Our results indicate the existence of at least two distinct pools of GSK-3beta in soleus muscle, one phosphorylated by PKA and another by PKB. Further, we hypothesise that each of these pools is involved in the control of different cellular processes.
Jensen
Jørgen
J
Department of Physiology, National Institute of Occupational Health, P.O. Box 8149 Dep., N-0033, Oslo, Norway. jorgen.jensen@stami.no
Brennesvik
Erlend O
EO
Lai
Yu-Chiang
YC
Shepherd
Peter R
PR
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004789:Enzyme Activation; D004837:Epinephrine / Q000494:pharmacology*; D006006:Glycogen Synthase / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D020662:Guanine Nucleotide Exchange Factors / Q000037:antagonists & inhibitors; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D013873:Thionucleotides / Q000494:pharmacology; D000077191:Wortmannin
D000730:Androstadienes; D003994:Bucladesine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D004837:Epinephrine; D006006:Glycogen Synthase; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D020662:Guanine Nucleotide Exchange Factors; D007328:Insulin; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D013873:Thionucleotides; D000077191:Wortmannin; C488718:2'-O-methyl-8-(4-chlorophenylthio)cAMP; C482601:Epac protein, mouse; C050086:N(6)-benzoyl-cyclic AMP; C000605507:Gsk3b protein, mouse; C000605508:Gsk3b protein, rat; C448021:glycogen synthase kinase 3 alpha