Submitted on July 28, 2006
Accepted on February 16, 2007
Gastrin regulates the TFF2 promoter through gastrin-responsive cis-acting elements and multiple signaling pathways
Shuiping Tu1, Alfred L Chi2, SeonHee Lim3, Guanglin Cui4, Zina Dubeykovskaya4, Wandong Ai3, John V Fleming3, Shigeo Takaishi3, and Timothy C. Wang5*
1 Medicine, Columbia University, NY, New York, United States
2 Medicine, Columbia University, New Yokr, New York, United States
3 New York, New York, United States; Medicine, Columbia University, New Yokr, New York, United States
4 New York, New York, United States; Medicine, Columbia University, NY, New York, United States
5 Division of Digestive and Liver Diseases, Columbia University College of Physicians and Surgeons, New York, New York, United States
* To whom correspondence should be addressed. E-mail: tcw21{at}columbia.edu.
Background: Trefoil family factor 2 (TFF2) is expressed in gastrointestinal epithelial cells where it serves to maintain mucosal integrity and promote epithelial repair. The peptide hormone, gastrin, stimulates acid secretion but also induces proliferation of the acid secreting mucosa. Since the relationship between these peptides of overlapping function is not understood, we chose to investigate the regulatory effect of gastrin on TFF2 expression. Methods: The expression of mRNA and protein of TFF2 was determined by RT-PCR and immunohistochemical staining, respectively. A series of truncated and mutant murine TFF2 promoter constructs was generated. Promoter activity was assessed using dual luciferase reporter assays. Gastrin-responsive DNA binding sites in the TFF2 promoter were evaluated by electrophoretic mobility shift assay (EMSA). Results: Gastrin significantly increased the level of endogenous mRNA of TFF2 in the gastrin receptor-expressing AGS-E gastric cancer cell line in a time- and dose- dependent manner. TFF2 protein expression in the gastric fundus was elevated in hypergastrinemic (INS-GAS) transgenic mice, and reduced in gastrin deficient mice. Gastrin treatment increased TFF2 promoter activity through cis-acting regions, containing CCAATA- and GC-rich enhancers. Pretreatment with YF476, a gastrin/CCKB receptor antagonist, abolished gastrin-dependent promoter activity. Inhibitors of PKC, MEK1 and PI3 kinase reduced gastrin-dependent TFF2 promoter activity, whereas an EGFR inhibitor had no effect. Conclusion: Gastrin regulates TFF2 transcription through a GC-rich DNA binding site and a PKC-, MEk1- and PI3 kinase-dependent but EGFR -independent pathway. Regulation of TFF2 by gastrin may play a role in the maintenance and repair of the gastrointestinal mucosa.
