Mechanism of Prostaglandin(PG)E_2-Induced Prolactin Expression in Human T Cells: Cooperation of Two PGE_2 Receptor Subtypes,E-Prostanoid(EP)3 and EP4,Via Calcium-and Cyclic Adenosine 5'-Monophosphate-Mediated Signaling Pathways

摘要

We previously reported that prolactin gene expression in the T-leukemic cell line Jurkat is stimulated by PGE_2 and that cAMP acts synergistically with Ca~(2+)or protein kinase C on the activation of the upstream prolactin promoter.Using the transcription inhibitor actinomycin D,we now show that PGE_2-induced prolactin expression requires de novo prolactin mRNA synthesis and that PGE_2 does not influence prolactin mRNA stability.Furthermore,PGE_2-induced prolactin expression was inhibited by protein kinase inhibitor fragment 14-22 and B APT A-AM,which respectively,inhibit protein kinase A-and Ca~(2+)-mediated signaling cascades.Using specific PGE_2 receptor agonists and antagonists,we show that PGE_2 induces prolactin expression through engagement of E-prostanoid(EP)3 and EP4 receptors.We also found that PGE_2 induces an increase in intracellular cAMP concentration as well as intracellular calcium concentration via EP4 and EP3 receptors,respectively.In transient transfections,3000 bp flanking the leukocyte prolactin promoter conferred a weak induction of the luciferase reporter gene by PGE_2 and cAMP,whereas cAMP in synergy with ionomycin strongly activated the promoter.Mutation of a C/EBP responsive element at-214 partially abolished the response of the leukocyte prolactin promoter to PGE_2,cAMP,and ionomycin plus cAMP.