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KLF4 positively regulates human ghrelin expression.
Hyo Jung Lee1, Young Mi Kang, Chang Suk Moon
1Division of Metabolic Disease, Department of Biomedical Science, National Institute of Health, 5 Nokbun-dong, Eunpyung-gu, Seoul, South Korea.
The Biochemical Journal
|March 31, 2009
Summary
Krüppel-like factor 4 (KLF4) positively regulates ghrelin expression. This study identifies a specific region in the ghrelin promoter where KLF4 binds, influencing ghrelin gene activity and metabolic functions.
Area of Science:
- Endocrinology
- Molecular Biology
- Gene Regulation
Background:
- Ghrelin, the endogenous ligand for the growth hormone secretagogue receptor, plays a critical role in metabolic regulation, including appetite and energy balance.
- Despite its significant biological functions, the precise mechanisms governing ghrelin gene expression remain largely unelucidated.
- Both ghrelin and Krüppel-like factor 4 (KLF4) are predominantly expressed in the stomach, suggesting a potential regulatory relationship.
Purpose of the Study:
- To investigate the association between ghrelin expression and Krüppel-like factor 4 (KLF4).
- To determine if KLF4 directly regulates human ghrelin gene promoter activity.
- To identify the specific region within the ghrelin promoter responsive to KLF4.
Main Methods:
- Comparative analysis of ghrelin and KLF4 tissue distribution.
- Assessment of ghrelin expression following butyrate treatment and fasting.
- Luciferase reporter assays to evaluate KLF4's effect on human ghrelin promoter activity in gastric cancer cells.
- Site-directed mutagenesis and deletion analysis of the ghrelin promoter.
- Electrophoretic mobility shift assays (EMSA) to confirm KLF4 binding to the promoter.
Main Results:
- Tissue distribution of ghrelin expression correlated with KLF4 expression.
- Butyrate and fasting, known to influence KLF4 and ghrelin levels respectively, modulated ghrelin expression.
- KLF4 significantly enhanced human ghrelin promoter activity in a dose-dependent manner.
- A specific KLF4-responsive element was identified between nucleotides -1228 and -1105 of the ghrelin promoter.
- EMSA confirmed direct binding of KLF4 to the -1165/-1146 region of the ghrelin promoter.
Conclusions:
- KLF4 acts as a positive regulator of human ghrelin gene expression.
- KLF4 directly binds to a specific regulatory region within the ghrelin promoter, mediating its transcriptional activity.
- These findings elucidate a novel mechanism for ghrelin gene regulation, with implications for understanding metabolic control.
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