title: Expressions of inhibitory Smads, Smad6 and Smad7, are differentially regulated by TPA in human lung fibroblast cells.
abstract: Smad6 and Smad7 are inhibitory Smads (I-Smads) with differential inhibitory effects on the regulation of the cellular signalings induced by TGF-beta superfamily. Here, we show that phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) down-regulates Smad6 mRNA expression and up-regulates Smad7 mRNA expression in IMR-90, a human lung fibroblast cell line. These regulations of I-Smads by TPA were suppressed by one PKC inhibitor (Gö6983), but not by another (Gö6976). TPA treatment had little effect on the phosphorylation of novel PKCs (PKCdelta and PKCepsilon), but specifically induced PKCmu phosphorylation, and this effect was inhibited by Gö6983, but not by Gö6976. Additionally, Gö6983 but not Gö6976 inhibited ERK- and JNK-phosphorylation as well as Smad7 promoter activity induced by TPA. MEK inhibitor U0126 inhibited the down-regulation of Smad6 mRNA expression but not the up-regulation of Smad7 mRNA expression. In contrast, JNK inhibitor SP600125 had no such effects. Luciferase reporter analysis revealed that TPA did not induce NF-kappaB activation. In addition, TPA up-regulated Smad7 expression in the presence of NF-kappaB inhibitor TLCK. These findings indicate that TPA down-regulates Smad6 expression presumably via PKCmu-ERK-dependent pathway and up-regulates Smad7 expression via PKCmu-dependent mechanism(s) which need no MAPK and NF-kappaB activation.
authors.affiliation: Age Dimension Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8566, Japan. h-tsunobuchi@aist.go.jp
authors.forename: Hironaka
authors.initials: H
authors.lastname: Tsunobuchi
authors.forename: Akira
authors.initials: A
authors.lastname: Ishisaki
authors.forename: Toru
authors.initials: T
authors.lastname: Imamura
mesh_terms: D015153:Blotting, Western; D002070:Butadienes / Q000494:pharmacology; D002227:Carbazoles / Q000494:pharmacology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008156:Luciferases / Q000378:metabolism; D008168:Lung / Q000166:cytology*; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051905:Smad6 Protein; D051906:Smad7 Protein; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D015534:Trans-Activators / Q000096:biosynthesis*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism; D053773:Transforming Growth Factor beta1; D015854:Up-Regulation
chemical_list: D002070:Butadienes; D002227:Carbazoles; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D007211:Indoles; D016328:NF-kappa B; D009570:Nitriles; D012333:RNA, Messenger; C497802:SMAD6 protein, human; C497806:SMAD7 protein, human; D051905:Smad6 Protein; D051906:Smad7 Protein; C508960:TGFB1 protein, human; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; C113580:U 0126; C081021:Go 6976; D008156:Luciferases; D020928:Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate