Transforming growth factor-beta1 represses E-cadherin production via slug expression in lens epithelial cells.
OBJECTIVE
TGFbeta is a potent candidate for epithelial-mesenchymal transition (EMT) during the development of anterior polar cataracts in the human lens. The Snail superfamily is involved in EMT through the repression of E-cadherin production. This study was conducted to determine whether the Snail gene family is activated in the process of TGFbeta1-induced EMT and how TGFbeta1 regulates the expression of this gene family.


METHODS
Total RNA extracted from human cataract samples was subjected to the real-time PCR quantification of Slug mRNA. Induction of Slug expression by TGFbeta1 (10 ng/mL) in lens epithelial cells was determined by RT-PCR, immunostaining, immunoblot analysis, and Slug promoter analysis. A series of Slug promoter deletion constructs was used to identify the putative regulatory element responsive to TGF signaling. Chromatin immunoprecipitation was performed to determine whether Sp1 associates with the endogenous Slug promoter. Inhibition of Slug expression with Slug siRNA was used to investigate the role of Slug in TGFbeta-mediated EMT.


RESULTS
Slug levels were highly upregulated in lens epithelial cells obtained from patients with anterior polar cataracts. Treatment of TGFbeta1 induced the expression of Slug in both lens and other epithelial cells in vitro. TGFbeta1-induced Slug expression was significantly inhibited by the MEK- and JNK/SAPK-specific inhibitors, but not by transfection with dominant-negative forms of Smads or small GTPase proteins, indicating that MAPK pathways are involved in the regulation of Slug expression by TGFbeta1. The Slug promoter analysis revealed that the Sp1 binding site in the Slug promoter is responsible for TGFbeta1-induced Slug expression. In addition, the TGFbeta1-mediated repression of E-cadherin was significantly inhibited by Slug siRNA.


CONCLUSIONS
These data suggest that TGFbeta1 induces Slug expression and that the repression of E-cadherin production by TGFbeta1 is mediated by the induction of Slug in lens epithelial cells.
Choi
Jongkyu
J
Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul, Korea.
Park
Sun Young
SY
Joo
Choun-Ki
CK
D000818:Animals; D015153:Blotting, Western; D015820:Cadherins / Q000096:biosynthesis*; D002386:Cataract / Q000473:pathology; D002460:Cell Line; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000494:pharmacology*; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation / Q000187:drug effects*; D020868:Gene Silencing; D006801:Humans; D007908:Lens, Crystalline / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071250:Snail Family Transcription Factors; D016329:Sp1 Transcription Factor / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D000099222:betaIG-H3 Protein
D015820:Cadherins; D016326:Extracellular Matrix Proteins; D020928:Mitogen-Activated Protein Kinases; D012333:RNA, Messenger; D000071250:Snail Family Transcription Factors; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D000099222:betaIG-H3 Protein; C000604407:SNAI1 protein, human; C000604450:Snai2 protein, rat