title: Urea-inducible Egr-1 transcription in renal inner medullary collecting duct (mIMCD3) cells is mediated by extracellular signal-regulated kinase activation.
abstract: Urea (200-400 milliosmolar) activates transcription, translation of, and trans-activation by the immediate-early gene transcription factor Egr-1 in a renal epithelial cell-specific fashion. The effect at the transcriptional level has been attributed to multiple serum response elements and their adjacent Ets motifs located within the Egr-1 promoter. Elk-1, a principal ternary complex factor and Ets domain-containing protein, is a substrate of the extracellular signal-regulated kinase (ERK) mitogen-activated protein kinases. In the renal medullary mIMCD3 cell line, urea (200-400 milliosmolar) activated both ERK1 and ERK2 as determined by in-gel kinase assay and immune-complex kinase assay of epitope-tagged] ERK1 and ERK2. Importantly, urea did not affect abundance of either ERK. Urea-inducible Egr-1 transcription was a consequence of ERK activation because the ERK-specific inhibitor, PD98059, abrogated transcription from the murine Egr-1 promoter in a luciferase reported gene assay. In addition, activators of protein kinase A, including forskolin and 8-Br-cAMP, which are known to inhibit ERK-mediated events, also inhibited urea-inducible Egr-1 transcription. Furthermore, urea-inducible activation of the physiological ERK substrate and transcription factor, Elk-1, was demonstrated through transient cotransfection of a chimeric Elk-1/GAL4 expression plasmid and a GAL4-driven luciferase reporter plasmid. Taken together, these data indicate that, in mIMCD3 cells, urea activates ERKs and the ERK substrate, Elk-1, and that ERK inhibition abrogates urea-inducible Egr-1 transcription. These data are consistent with a model of urea-inducible renal medullary gene expression wherein sequential activation of ERKs and Elk-1 results in increased transcription of Egr-1 through serum response element/Ets motifs.
authors.affiliation: Division of Nephrology, Oregon Health Sciences University, Portland, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Cohen
mesh_terms: D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics*; D051766:Early Growth Response Protein 1; D004789:Enzyme Activation / Q000187:drug effects; D005419:Flavonoids / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D017874:Immediate-Early Proteins; D007679:Kidney Medulla / Q000166:cytology / Q000502:physiology*; D007685:Kidney Tubules, Collecting / Q000502:physiology*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D011480:Protease Inhibitors / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects; D014508:Urea / Q000494:pharmacology; D014882:Water-Electrolyte Balance; D050807:ets-Domain Protein Elk-1
chemical_list: D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; C494113:Elk1 protein, mouse; D005419:Flavonoids; D017874:Immediate-Early Proteins; D011480:Protease Inhibitors; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D014508:Urea; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one