EP(3) prostanoid receptor isoforms utilize distinct mechanisms to regulate ERK 1/2 activation.
Prostaglandin-E(2) (PGE(2)) is a hormone derived from the metabolism of arachidonic acid whose functions include regulation of platelet aggregation, fever and smooth muscle contraction/relaxation. PGE(2) mediates its physiological and pathophysiological effects through its binding to four G-protein coupled receptor subtypes, named EP(1), EP(2), EP(3) and EP(4). The EP(3) prostanoid receptor is unique in that it has multiple isoforms generated by alternative mRNA splicing. These splice variants display differences in tissue expression, constitutive activity and regulation of signaling molecules. To date there are few reports identifying differential activities of EP(3) receptor isoforms and their effects on gene regulation. We generated HEK cell lines expressing the human EP(3-Ia), EP(3-II) or EP(3-III) isoforms. Using immunoblot analysis we found that nM concentrations of PGE(2) strongly stimulated the phosphorylation of ERK 1/2 by the EP(3-II) and EP(3-III) isoforms; whereas, ERK 1/2 phosphorylation by the EP(3-Ia) isoform was minimal and only occurred at muM concentrations of PGE(2). Furthermore, the mechanisms of the PGE(2) mediated phosphorylation of ERK 1/2 by the EP(3-II) and EP(3-III) isoforms were different. Thus, PGE(2) stimulation of ERK 1/2 phosphorylation by the EP(3-III) isoform involves activation of a Galpha(i)/PI3K/PKC/Src and EGFR-dependent pathway; while for the EP(3-II) isoform it involves activation of a Galpha(i)/Src and EGFR-dependent pathway. These differences result in unique differences in the regulation of reporter plasmid activity for the downstream effectors ELK1 and AP-1 by the EP(3-II) and EP(3-III) prostanoid receptor isoforms.
Department of Pharmacology and Toxicology, The University of Arizona, College of Pharmacy, 1703 E. Mabel St., Tucson, AZ 85721, USA.
Davelene D
DD
Israel
John W
JW
Regan
D002478:Cells, Cultured; D000242:Cyclic AMP; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D015151:Immunoblotting; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D010766:Phosphorylation; D020033:Protein Isoforms; D011869:Radioligand Assay; D018078:Receptors, Prostaglandin E / Q000235:genetics / Q000378:metabolism*; D058308:Receptors, Prostaglandin E, EP3 Subtype; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D050807:ets-Domain Protein Elk-1 / Q000235:genetics / Q000378:metabolism
C494112:ELK1 protein, human; C545647:PTGER3 protein, human; D020033:Protein Isoforms; D018078:Receptors, Prostaglandin E; D058308:Receptors, Prostaglandin E, EP3 Subtype; D018808:Transcription Factor AP-1; D050807:ets-Domain Protein Elk-1; D000242:Cyclic AMP; D008156:Luciferases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3