Sp1 and Smad3 are required for high glucose-induced p21WAF1 gene transcription in LLC-PK1 cells

✍ Scribed by Tsai-Der Chuang; Jinn-Yuh Guh; Shean-Jaw Chiou; Hung-Chun Chen; Wen-Chun Hung; Lea-Yea Chuang

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 372 KB
• Volume: 102
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.21346

✦ Synopsis

Abstract

The cyclin‐dependent kinase inhibitor p21^WAF1^ is required for diabetic glomerular hypertrophy. High glucose‐induced hypertrophy in proximal tubule cells is dependent on transforming growth factor‐β (TGF‐β). Many of the TGF‐β‐induced effects are dependent on Smad2/3. Thus, the molecular mechanisms of high glucose‐induced p21^WAF1^ and hypertrophy were studied in high glucose‐cultured proximal tubule‐like LLC‐PK~1~ cells. We found that high glucose (30 mM) induced hypertrophy at 72 h. High glucose also increased the expression of p21^WAF1^ protein and p21^WAF1^ mRNA transcription and abundance at 48 h. The DNA element in the 5′ regulatory region of p21^WAF1^ gene essential for high glucose‐induced p21^WAF1^ gene transcription was identified as Sp1 by a series of the 5′ regulatory region of p21^WAF1^ gene deletion mutants. Moreover, high glucose activated Smad2/3 while increasing the Sp1 DNA‐binding activity. High glucose also increased the Sp1‐dependent transcriptional activity of p21^WAF1^ gene. High glucose‐induced hypertrophy was attenuated by p21^WAF1^ short interfering RNA and Smad3 dominant‐negative plasmid transfection. We concluded that high glucose induced hypertrophy via Sp1‐Smad2/3‐dependent activation of p21^WAF1^ gene transcription in LLC‐PK~1~ cells. J. Cell. Biochem. 102: 1190–1201, 2007. © 2007 Wiley‐Liss, Inc.