title: GSK-3beta regulation in skeletal muscles by adrenaline and insulin: evidence that PKA and PKB regulate different pools of GSK-3.
abstract: 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.
authors.affiliation: Department of Physiology, National Institute of Occupational Health, P.O. Box 8149 Dep., N-0033, Oslo, Norway. jorgen.jensen@stami.no
authors.forename: Jørgen
authors.initials: J
authors.lastname: Jensen
authors.forename: Erlend O
authors.initials: EO
authors.lastname: Brennesvik
authors.forename: Yu-Chiang
authors.initials: YC
authors.lastname: Lai
authors.forename: Peter R
authors.initials: PR
authors.lastname: Shepherd
mesh_terms: 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
chemical_list: 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