TY - JOUR
T1 - GSK-3β regulation in skeletal muscles by adrenaline and insulin
T2 - Evidence that PKA and PKB regulate different pools of GSK-3
AU - Jensen, Jørgen
AU - Lai, Yu Chiang
AU - Brennesvik, Erlend O.
AU - Shepherd, Peter R.
PY - 2007/1/1
Y1 - 2007/1/1
N2 - 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-3β Ser9 and GSK-3α 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-3β 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 μM) blocked insulin-stimulated GSK-3 phosphorylation completely, but adrenaline increased GSK-3β Ser9 phosphorylation in the presence of wortmannin. The PKA inhibitor H89 (50 μM) reduced adrenaline-stimulated GSK-3β 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-3β 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.
AB - 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-3β Ser9 and GSK-3α 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-3β 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 μM) blocked insulin-stimulated GSK-3 phosphorylation completely, but adrenaline increased GSK-3β Ser9 phosphorylation in the presence of wortmannin. The PKA inhibitor H89 (50 μM) reduced adrenaline-stimulated GSK-3β 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-3β 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.
KW - 8-pCPT-2′-O-Me-cAMP
KW - AKAP
KW - Akt
KW - cAMP
KW - Glycogen synthase kinase
KW - GSK3
UR - http://www.scopus.com/inward/record.url?scp=33845305818&partnerID=8YFLogxK
U2 - 10.1016/j.cellsig.2006.06.006
DO - 10.1016/j.cellsig.2006.06.006
M3 - Article
C2 - 16934435
AN - SCOPUS:33845305818
SN - 0898-6568
VL - 19
SP - 204
EP - 210
JO - Cellular Signalling
JF - Cellular Signalling
IS - 1
ER -