| Summary: | 碩士 === 國防醫學院 === 生物化學研究所 === 104 === The tumor suppressor p53 plays an important role in the regulation of proliferation, apoptosis, and metabolism in human cells. The sodium-dependent glucose cotransporter 1 (SGLT1) play a crucial role in glucose uptake in intestinal and kidney tubular epithelial cells, respectively. Previous studies indicate that p53 protein significantly down-regulates the expression and activity of the facilitate glucose transporter proteins, including GLUT1, GLUT2, GLUT3, and GLUT4. However, the effect and mechanisms of p53 on regulation of SGLTs expression are still not understood. To understand the metabolic role of p53 protein in the active absorption of glucose from exterior environments, the effect of p53 on the function and gene expression of SGLT1 was investigated. In this study, the cultured human intestinal cell HCT116, which are known to express WT-p53 protein were used. To investigate the effect of p53 protein on SGLT1 gene expression, the p53 protein was induced in using doxorubicin, 5-fluorouracil, and the inhibited by pifithrin-α. The wild type (WT) or mutant p53 protein were also overexpressed using WT- or mutant-p53 vectors. In addition, the p53-KO HCT116 cells were also used. Western blot and Q-PCR analysis were used to analyze the induction and inhibition of p53 mRNA and protein levels in these cells. Moreover, the effect of different p53 status on glucose uptake were examined. Transient transfection analysis further used to analyze a series of SGLT1 promoter constructs to investigated the sequence elements and transcription factors that are involved in the p53-mediated effects. Our results showed that the expression of SGLT1 is increased with increasing p53 protein level. In addition, quantitative PCR also revealed a pronounced increase in SGLT1 mRNA levels following p53 induction. Further studies using the luciferase reporters showed that the similar induction of SGLT1 promoter activities by p53 protein. These results suggest that the p53-mediated induction of SGLT1 is regulated primarily at the transcriptional level. Further studies are performed to identify the promoter elements and transcription factors that are involved in p53-mediated induction. In conclusion, we demonstrate that p53 palys a significant role in the expression of SGLT1. Our results also extended the metabolic significance of p53 to whole body glucose homeostasis.
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