TY - JOUR
T1 - Phosphorylation of glycogen synthase kinase-3 and stimulation of T-cell factor signaling following activation of EP2 and EP4 prostanoid receptors by prostaglandin E2
AU - Fujino, Hiromichi
AU - West, Kimberly A.
AU - Regan, John W.
PY - 2002/1/25
Y1 - 2002/1/25
N2 - Recently we have shown that the FPB prostanoid receptor, a G-protein-coupled receptor that couples to Gαq, activates T-cell factor (Tcf)/lymphoid enhancer factor (Lef)-mediated transcriptional activation (Fujino, H., and Regan, J. W. (2001) J. Biol. Chem. 276, 12489-12492). We now report that the EP2 and EP4 prostanoid receptors, which couple to Gαs, also activate Tcf/Lef signaling. By using a Tcf/Lef-responsive luciferase reporter gene, transcriptional activity was stimulated ∼10-fold over basal by 1 h of treatment with prostaglandin E2 (PGE2) in HEK cells that were stably transfected with the human EP2 and EP4 receptors. This stimulation of reporter gene activity was accompanied by a PGE2-dependent increase in the phosphorylation of both glycogen synthase kinase-3 (GSK-3) and Akt kinase. H-89, an inhibitor of protein kinase A (PKA), completely blocked the agonist-dependent phosphorylation of GSK-3 in both EP2- and EP4-expressing cells. However, H-89 pretreatment only blocked PGE2-stimulated Lef/Tcf reporter gene activity by 20% in EP4-expressing cells compared with 65% inhibition in EP2-expressing cells. On the other hand wortmannin, an inhibitor of phosphatidylinositol 3-kinase, had the opposite effect and inhibited PGE2-stimulated reporter gene activity to a much greater extent in EP4-expressing cells as compared with EP2-expressing cells. These findings indicate that the activation of Tcf/Lef signaling by EP2 receptors occurs primarily through a PKA-dependent pathway, whereas EP4 receptors activate Tcf/Lef signaling mainly through a phosphatidylinositol 3-kinase-dependent pathway. This is the first indication of a fundamental difference in the signaling potential of EP2 and EP4 prostanoid receptors.
AB - Recently we have shown that the FPB prostanoid receptor, a G-protein-coupled receptor that couples to Gαq, activates T-cell factor (Tcf)/lymphoid enhancer factor (Lef)-mediated transcriptional activation (Fujino, H., and Regan, J. W. (2001) J. Biol. Chem. 276, 12489-12492). We now report that the EP2 and EP4 prostanoid receptors, which couple to Gαs, also activate Tcf/Lef signaling. By using a Tcf/Lef-responsive luciferase reporter gene, transcriptional activity was stimulated ∼10-fold over basal by 1 h of treatment with prostaglandin E2 (PGE2) in HEK cells that were stably transfected with the human EP2 and EP4 receptors. This stimulation of reporter gene activity was accompanied by a PGE2-dependent increase in the phosphorylation of both glycogen synthase kinase-3 (GSK-3) and Akt kinase. H-89, an inhibitor of protein kinase A (PKA), completely blocked the agonist-dependent phosphorylation of GSK-3 in both EP2- and EP4-expressing cells. However, H-89 pretreatment only blocked PGE2-stimulated Lef/Tcf reporter gene activity by 20% in EP4-expressing cells compared with 65% inhibition in EP2-expressing cells. On the other hand wortmannin, an inhibitor of phosphatidylinositol 3-kinase, had the opposite effect and inhibited PGE2-stimulated reporter gene activity to a much greater extent in EP4-expressing cells as compared with EP2-expressing cells. These findings indicate that the activation of Tcf/Lef signaling by EP2 receptors occurs primarily through a PKA-dependent pathway, whereas EP4 receptors activate Tcf/Lef signaling mainly through a phosphatidylinositol 3-kinase-dependent pathway. This is the first indication of a fundamental difference in the signaling potential of EP2 and EP4 prostanoid receptors.
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U2 - 10.1074/jbc.M109440200
DO - 10.1074/jbc.M109440200
M3 - Article
C2 - 11706038
AN - SCOPUS:0037169557
SN - 0021-9258
VL - 277
SP - 2614
EP - 2619
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 4
ER -