Hypotonicity activates transcription through ERK-dependent and -independent pathways in renal cells.
Acute hypotonic shock (50% dilution of medium with sterile water, but not with isotonic NaCl) activated the extracellular signal response kinase (ERK) mitogen-activated protein (MAP) kinases in renal medullary cells, as measured by Western analysis with a phospho-ERK-specific antibody and by in vitro kinase assay of epitope-tagged ERKs immunoprecipitated from stable HA-ERK transfectants. Hypotonicity also activated the transcription factor and ERK substrate Elk-1 in a partially PD-98059-sensitive fashion, as assessed by chimeric reporter gene assay. Consistent with these data, hypotonic stress activated transcription of the immediate-early gene transcription factor Egr-1 in a partially PD-98059-sensitive fashion. Hypotonicity-inducible Egr-1 transcription was mediated in part through 5'-flanking regions containing serum response elements and in part through the minimal Egr-1 promoter. Elimination of the Ets motifs adjacent to key regulatory serum response elements in the Egr-1 promoter diminished the effect of hypotonicity but failed to abolish it. Interestingly, hypotonicity also transiently activated p38 and c-Jun NH2-terminal kinase 1, as determined by immunoblotting with anti-phospho-MAP kinase antibodies. Taken together, these data strongly suggest that hypotonicity activates immediate-early gene transcription in renal medullary cells via MAP kinase kinase-dependent and -independent mechanisms.
Zhang
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Divisions of Nephrology and Molecular Medicine, Oregon Health Sciences University and Portland Veterans Affairs Medical Center, Portland, Oregon 97201, USA.
Yang
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Cohen
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D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D051766:Early Growth Response Protein 1; D004789:Enzyme Activation; D017930:Genes, Reporter; D006801:Humans; D007038:Hypotonic Solutions; D017874:Immediate-Early Proteins; D007679:Kidney Medulla; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014508:Urea / Q000494:pharmacology; D016335:Zinc Fingers; D050807:ets-Domain Protein Elk-1
D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; C494112:ELK1 protein, human; D051766:Early Growth Response Protein 1; D007038:Hypotonic Solutions; D017874:Immediate-Early Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion 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