Hepatocyte nuclear factor 4α regulates the expression of intestinal epithelial Na+/H+ exchanger isoform 3

Author:

Muthusamy Saminathan1,Jeong Jong Jin1,Cheng Ming1,Bonzo Jessica A.2,Kumar Anoop1,Gonzalez Frank J.2,Borthakur Alip1ORCID,Dudeja Pradeep K.13,Saksena Seema13,Malakooti Jaleh3

Affiliation:

1. Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois

2. Center for Cancer Research, National Cancer Institute, Bethesda, Maryland

3. Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois

Abstract

Na+/H+ exchanger isoform 3 (NHE3) plays a key role in coupled electroneutral NaCl absorption in the mammalian intestine. Reduced NHE3 expression or function has been implicated in the pathogenesis of diarrhea associated with inflammatory bowel disease (IBD) or enteric infections. Our previous studies revealed transcriptional regulation of NHE3 by various agents such as TNF-α, IFN-γ, and butyrate involving transcription factors Sp1 and Sp3. In silico analysis revealed that the NHE3 core promoter also contains a hepatocyte nuclear factor 4α (HNF-4α) binding site that is evolutionarily conserved in several species suggesting that HNF-4α has a role in NHE3 regulation. Nhe3 mRNA levels were reduced in intestine-specific Hnf4α-null mice. However, detailed mechanisms of NHE3 regulation by HNF-4α are not known. We investigated the regulation of NHE3 gene expression by HNF-4α in vitro in the human intestinal epithelial cell line C2BBe1 and in vivo in intestine-specific Hnf4α-null ( Hnf4αΔIEpC) and control ( Hnf4αfl/fl) mice. HNF-4α knockdown by short interfering RNA in C2BBe1 cells significantly decreased NHE3 mRNA and NHE3 protein levels. Gel mobility shift and chromatin immunoprecipitation assays revealed that HNF-4α directly interacts with the HNF-4α motif in the NHE3 core promoter. Site-specific mutagenesis on the HNF-4α motif decreased, whereas ectopic overexpression of HNF-4α increased, NHE3 promoter activity. Furthermore, loss of HNF-4α in Hnf4αΔIEpC mice decreased colonic Nhe3 mRNA and NHE3 protein levels. Our results demonstrate a novel role for HNF-4α in basal regulation of NHE3 expression. These studies represent an important and novel target for therapeutic intervention in IBD-associated diarrhea. NEW & NOTEWORTHY Our studies for the first time show that hepatocyte nuclear factor 4α directly regulates NHE3 promoter activity and its basal expression in the intestine.

Funder

HHS | NIH | National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Health Services Research and Development (Veterans Health Administration HSR and D)

Publisher

American Physiological Society

Subject

Physiology (medical),Gastroenterology,Hepatology,Physiology

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