title: Transcriptional activation of the human claudin-18 gene promoter through two AP-1 motifs in PMA-stimulated MKN45 gastric cancer cells.
abstract: Claudin-18 (CLDN18), a member of the claudin family of proteins that are structural components of tight junctions, has two alternatively spliced variants, claudin-18a1 and claudin-18a2, which are highly expressed in lung and stomach, respectively. Downregulation of claudin-18a2 is associated with gastric cancers of an intestinal phenotype; however, the mechanisms regulating its expression have not been defined. Here, we found that phorbol 12-myristate 13-acetate (PMA) treatment of MKN45 human gastric cancer cell line increased claudin-18a2 expression. In addition, this study aimed to characterize the human CLDN18a2 promoter. Using reporter gene assays and deletion analysis, we mapped the critical promoter region of the PMA-stimulated claudin-18a2 expression to the -923/-286 region. Electrophoretic mobility shift assays and mutational analyses revealed that two activator protein (AP)-1 binding sites played an important role in the expression of claudin-18a2 in PMA-stimulated MKN45 cells. Protein kinase C (PKC) and mitogen-activated protein kinase (MAPK) inhibitors suppressed the upregulation of claudin-18a2. These results indicate that the PKC/MAPK/AP-1 dependent pathway regulates claudin-18a2 expression in gastric cells.
authors.affiliation: Department of Bioengineering Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Yano
authors.forename: Takashi
authors.initials: T
authors.lastname: Imaeda
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Niimi
mesh_terms: D024506:5' Flanking Region / Q000187:drug effects; D001483:Base Sequence; D002273:Carcinogens / Q000494:pharmacology*; D045744:Cell Line, Tumor; D057167:Claudins; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D017930:Genes, Reporter; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000187:drug effects*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013274:Stomach Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects*; D015854:Up-Regulation; D014746:Vimentin / Q000235:genetics / Q000378:metabolism
chemical_list: C486683:CLDN18 protein, human; D002273:Carcinogens; D057167:Claudins; D008565:Membrane Proteins; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D014746:Vimentin; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate