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. 2013 Mar 25;14(4):6542–6555. doi: 10.3390/ijms14046542

Figure 1.

Figure 1

Signaling pathways activated by PGE2 stimulation of the human EP2 and EP4 prostanoid receptors. Phosphorylation of GSK-3α via either PKA or PI3K signaling pathway inhibits the kinase activity of GSK-3α. Inhibition of GSK-3α stabilizes β-catenin that results in a decrease in its degradation and promotes β-catenin nuclear translocation and transcriptional activity of Tcf/Lef-regulated genes. Activation of either PKA or PI3K signaling pathway leads to phosphorylation of the transcription factor CREB regulating cAMP responsive gene expression. Activation of the PI3K/ERK pathway induces functional expression of EGR-1, known to regulate PGE2 synthase. In addition, PI3K signaling pathway inhibits the activity of PKA.