title: Mitochondrial cytochrome c release mediates ceramide-induced activator protein 2 activation and gene expression in keratinocytes.
abstract: The intracellular signaling pathway(s) through which second messenger ceramides induce gene expression in human cells has not yet been characterized. In the present study, ceramide-induced expression of intercellular adhesion molecule-1 (ICAM-1), which requires activation of transcription factor activator protein 2 (AP-2), was found to be mediated through a mitochondrial pathway. Inhibitors of mitochondrial electron transport chain (e.g. rotenone, thenoyltrifluoroacetone, and antimycin A) reduced ceramide-induced ICAM-1 expression. Stimulation of human keratinocytes with cell-permeant ceramides at concentrations that did not induce apoptosis (no activation of caspases 3, 8, and 9 and no nucleosomal fragmentation) but caused AP-2 activation and ICAM-1 induction released cytochrome c (cyt c) from mitochondria into the cytoplasm of cells. This cyt c release was an indispensable prerequisite for effective ceramide signaling, because its inhibition by modulating the mitochondrial megachannel with bonkrekic acid or carboxyatractyloside prevented ceramide-induced AP-2 activation and ICAM-1 expression. Analysis of the interaction between cyt c and AP-2 revealed that cyt c oxidized AP-2 and that this redox regulation greatly enhanced the DNA binding capacity of AP-2. Mitochondria thus have a previously unrecognized function in signaling ceramide-induced transcription factor activation and gene regulation.
authors.affiliation: Cell Biology, Institut fuer Umweltmedizinische Forschung, Heinrich-Heine-University gGmbH, Auf'm Hennekamp 50, D-40225 Duesseldorf, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Grether-Beck
authors.forename: Ingo
authors.initials: I
authors.lastname: Felsner
authors.forename: Heidi
authors.initials: H
authors.lastname: Brenden
authors.forename: Jean
authors.initials: J
authors.lastname: Krutmann
mesh_terms: D017209:Apoptosis; D001278:Atractyloside / Q000031:analogs & derivatives* / Q000494:pharmacology; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival; D002478:Cells, Cultured; D002518:Ceramides / Q000378:metabolism*; D004396:Coloring Agents / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004579:Electron Transport; D005347:Fibroblasts / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000096:biosynthesis; D015603:Keratinocytes / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D013997:Time Factors; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D002518:Ceramides; D004396:Coloring Agents; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D013778:Tetrazolium Salts; D013844:Thiazoles; D050656:Transcription Factor AP-2; D014157:Transcription Factors; D018799:Intercellular Adhesion Molecule-1; D001278:Atractyloside; D045304:Cytochromes c; D004247:DNA; C022616:thiazolyl blue; D005978:Glutathione; D010100:Oxygen; C003853:carboxyatractyloside