PGE2 induces c-fos expression by a cAMP-independent mechanism in glomerular mesangial cells.
Prostanoids induce expression of several immediate-early genes, but the molecular mechanisms underlying these responses remain poorly characterized. We studied induction of the proto-oncogene c-fos by PGE2 in mesangial cells as a model of gene regulation by prostanoids. PGE2 induced marked and transient accumulation of c-fos mRNA. Addition of exogenous 8-bromo-cAMP or forskolin failed to induce c-fos mRNA, suggesting that activation of an EP2 receptor linked to adenylate cyclase did not account for induction of c-fos by PGE2. These data contrast with previous experiments in NIH 3T3 cells in which PGE2 induced c-fos by a cAMP-dependent mechanism. Depletion of protein kinase C blocked induction of c-fos mRNA by PGE2, whereas a protein tyrosine kinase inhibitor had no effect. We further showed that PGE2 induces the c-fos gene by increasing the transactivating capacity of the serum-response element. Transient transfections with a CAT fusion gene driven by an AP-1 cis-element demonstrated that although PGE2 markedly induced c-fos, PGE2 did not increase AP-1-driven transcriptional responses. Electrophoretic gel mobility shift assays revealed that PGE2 failed to increase binding of AP-1 complexes to a consensus AP-1 DNA sequence. Taken together, these experiments provide evidence for a cAMP-independent, protein kinase C-dependent pathway linking a PGE2 receptor on the plasma membrane to transcriptional activation in the nucleus. Regulation of gene transcription by PGE2 probably involves c-fos induction without concomitant activation of AP-1.
Simonson
M S
MS
Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106.
Herman
W H
WH
Dunn
M J
MJ
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D001483:Base Sequence; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D015232:Dinoprostone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000187:drug effects*; D016762:Genes, fos; D016758:Genes, jun; D005920:Glomerular Mesangium / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009838:Oligodeoxyribonucleotides; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism; D019000:Phosphotyrosine; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D018078:Receptors, Prostaglandin E / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D016385:TATA Box; D018808:Transcription Factor AP-1 / Q000096:biosynthesis / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
D009838:Oligodeoxyribonucleotides; D010750:Phosphoproteins; D012333:RNA, Messenger; D018078:Receptors, Prostaglandin E; D018808:Transcription Factor AP-1; D005576:Colforsin; D019000:Phosphotyrosine; D015124:8-Bromo Cyclic Adenosine Monophosphate; D016718:Arachidonic Acid; D014443:Tyrosine; D000242:Cyclic AMP; D015232:Dinoprostone