Involvement of MAP kinase cascades in Smad7 transcriptional regulation.
Smad7 transcription is known to be regulated by TGF-beta to form a negative-feedback loop of TGF-beta-mediated biological responses. In this study, we sought to determine whether other signaling cascades, especially mitogen-activated protein (MAP) kinases, might be involved in the transcriptional regulation of Smad7. Hyperosmolarity (500 mOsm/kg H(2)O) or anisomycin (10 microg/ml) potentiated TGF-beta-induced increases of Smad7 mRNA abundance in normal rat kidney fibroblasts. SB203580 (10 microM) treatment had no effect on basal and TGF-beta-induced Smad7 mRNA abundance, and the overexpression of kinase-negative ATF2 had no effect on Smad7 promoter activity. On the other hand, overexpression of dominant-negative JNK and dominant-negative c-Jun significantly attenuated the TGF-beta-induced increases of Smad7 mRNA abundance and promoter activity, respectively. Mutations of the AP-1 element near the Smad-binding element in the rat Smad7 promoter also completely abolished TGF-beta-induced Smad7 promoter activity. These results suggested that the JNK cascade, not p38 kinase, cooperated with the Smad signaling to induce Smad7 transcription through the AP-1 element. Serum treatment (10%) attenuated the TGF-beta-induced Smad7 mRNA increase, and PD98059 (30 microM) treatment increased the basal and TGF-beta-induced Smad7 promoter activity. Gel shift analysis revealed that serum treatment decreased the amount of nuclear Smad complex that PD98059 treatment was shown to restore. These results indicated that ERK activation negatively regulated Smad7 transcription possibly by inhibiting translocation of Smad complex to nuclei. In conclusion, JNK cascade and ERK cascade are important positive and negative regulators of Smad7 transcription, respectively.
Uchida
K
K
Department of Medicine, Kidney Center, Tokyo Women's Medical University, 8-1 Kawada-cho Shinjuku-ku, Tokyo 162-8666, Japan. kuchida@kc.twmu.ac.jp
Suzuki
H
H
Ohashi
T
T
Nitta
K
K
Yumura
W
W
Nihei
H
H
D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D005799:Genes, Dominant; D007093:Imidazoles / Q000494:pharmacology; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D051906:Smad7 Protein; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007093:Imidazoles; D016755:Proto-Oncogene Proteins c-jun; D011725:Pyridines; D012333:RNA, Messenger; D051906:Smad7 Protein; C497808:Smad7 protein, rat; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D000841:Anisomycin; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one