title: Stimulation of the Ca2+-mediated egr-1 and c-fos expression in murine erythroleukaemia cells by cyclosporin A.
abstract: The Ca2+-induced expression of the primary response genes egr-1 and c-fos was investigated in the murine erythroleukaemia cell line ELM-I-1. Exposure of the cells to the Ca2+-ionophore A23187 led to a rapid transient rise in egr-1 and c-fos mRNA production followed by an increase in Egr-1 and c-Fos protein levels as well as an increase in Egr-1 and activator protein 1 (AP-1) DNA-binding activity. Preincubation of the cells with KN-62, a specific inhibitor of Ca2+/calmodulin-dependent protein kinases, strongly decreased the Ca2+-mediated expression of egr-1 and c-fos. In contrast, treatment with cyclosporin A, which inhibits the Ca2+/calmodulin-dependent protein phosphatase 2B or calcineurin, increased both egr-1 and c-fos mRNA production and the DNA-binding activity of the Egr-1 and AP-1 transcription factors in response to the intracellular Ca+ concentration ([Ca2+]i)-increasing agents A23187 or cyclopiazonic acid. Enhancement of the Ca2+-induced c-fos and egr-1 expression by cyclosporin A was correlated with the capability of this agent to inhibit calcineurin phosphatase activity in ELM-I-1 cells. Studies on the phosphorylation state and DNA-binding activity of the cAMP response element-binding protein (CREB) did not demonstrate an early Ca2+-dependent activation of this transcription factor, suggesting that the regulation of c-fos and egr-1 expression by Ca2+ is not linked to CREB in the haematopoietic ELM-I-1 cells. The results indicate that calcineurin exerts negative regulatory effects on both egr-1 and c-fos expression in murine erythroleukaemia cells, in addition to the calcineurin-mediated down-regulation of c-myb expression observed previously in this cell system. This study therefore emphasizes the important role of calcineurin as a negative modulator of gene expression in certain cell types.
authors.affiliation: Department of Toxicology, Hamburg University Medical School and Fraunhofer Department of Toxicology and Environmental Medicine, Grindelallee 117, D-20146 Hamburg, Germany. aschaefe@uke.uni-hamburg.de
authors.forename: A
authors.initials: A
authors.lastname: Schaefer
authors.forename: M
authors.initials: M
authors.lastname: Magócsi
authors.forename: A
authors.initials: A
authors.lastname: Fandrich
authors.forename: H
authors.initials: H
authors.lastname: Marquardt
mesh_terms: D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D065095:Calcineurin Inhibitors; D002118:Calcium / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D051766:Early Growth Response Protein 1; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D016762:Genes, fos; D017874:Immediate-Early Proteins / Q000235:genetics; D004915:Leukemia, Erythroblastic, Acute / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D016559:Tacrolimus / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
chemical_list: D065095:Calcineurin Inhibitors; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; D017874:Immediate-Early Proteins; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D000001:Calcimycin; D016572:Cyclosporine; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D017027:Protein Tyrosine Phosphatases; D002118:Calcium; D016559:Tacrolimus