Epidermal growth factor increases claudin-4 expression mediated by Sp1 elevation in MDCK cells.
Epidermal growth factor (EGF) increases claudin-4 expression in Madin-Darby canine kidney (MDCK) cells. Here we examined what regulatory mechanisms are involved in the EGF-induced claudin-4 elevation. EGF transiently increased claudin-4 mRNA at 3h and persistently increased its protein for 24h without affecting claudin-1 expression. EGF increased p-ERK1/2 levels, which were inhibited by U0126, a MEK inhibitor. The exogenous expression of constitutively activated MEK increased claudin-4 expression. These results indicate that the activation of ERK1/2 is involved in the EGF-induced claudin-4 elevation. EGF increased Sp1 expression within 1h, which was inhibited by U0126. In immunocytochemistry, Sp1 was distributed in nucleus in control and the EGF-treated cells. The EGF-induced claudin-4 elevation was inhibited by mithramycin, a Sp1 inhibitor, and Sp1 small interfering RNA. We suggest that EGF activates a MEK/ERK pathway and increases Sp1 expression, resulting in an elevation of claudin-4 expression.
Ikari
Akira
A
Department of Pharmaco-Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan. ikari@u-shizuoka-ken.ac.jp
Atomi
Kosuke
K
Takiguchi
Ayumi
A
Yamazaki
Yasuhiro
Y
Miwa
Masao
M
Sugatani
Junko
J
D000818:Animals; D002460:Cell Line; D062506:Claudin-4; D004285:Dogs; D004815:Epidermal Growth Factor / Q000378:metabolism* / Q000494:pharmacology; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D016329:Sp1 Transcription Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
D062506:Claudin-4; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D016329:Sp1 Transcription Factor; D004815:Epidermal Growth Factor; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3