Regulation of ATP-sensitive potassium channel subunit Kir6.2 expression in rat intestinal insulin-producing progenitor cells.
We have reported that the combined expression of Pdx-1 (pancreatic duodenal homeobox 1) and Isl-1 (islet 1) enables immature rat enterocytes (IEC-6) to produce and release insulin. A key component regulating the release of insulin is the ATP-sensitive potassium channel subunit Kir6.2. To investigate the regulation of Kir6.2 gene expression, we assessed Kir6.2 expression in IEC-6 cells expressing Pdx-1 and/or Isl-1. We observed that Kir6.2 protein was expressed de novo in IEC-6 cells expressing both Pdx-1 and Isl-1 but not in cells expressing Pdx-1 alone. Next, we analyzed the regions of the Kir6.2 promoter (-1677/-45) by performing a luciferase assay and electrophoretic mobility shift assay. The results have demonstrated that Kir6.2 promoter possesses two regions regulating the promoter activity: a Foxa2-binding site (-1364 to -1210) and an Sp1/Sp3-binding site (-1035 to -939). The additional expression of Isl-1 in IEC-6 cells expressing Pdx-1 attenuated overexpression of Foxa2 protein and enhanced Kir6.2 expression. Finally, knockdown of Isl-1 using the iRNA technique resulted in decreased expression of Kir6.2 protein in a rat pancreatic beta-cell line (RIN-5F cells). These results indicate that expression of Kir6.2 in the rat intestine is moderated by Isl-1.
Hashimoto
Tetsuya
T
Division of Endocrinology and Metabolism, Department of Medicine, Shiga University of Medical Science, Otsu, Japan.
Nakamura
Takaaki
T
Maegawa
Hiroshi
H
Nishio
Yoshihiko
Y
Egawa
Katsuya
K
Kashiwagi
Atsunori
A
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D004247:DNA; D017931:DNA Primers; D024202:Electrophoretic Mobility Shift Assay; D005786:Gene Expression Regulation / Q000502:physiology*; D018398:Homeodomain Proteins / Q000502:physiology; D007328:Insulin / Q000096:biosynthesis*; D007413:Intestinal Mucosa / Q000378:metabolism*; D060850:LIM-Homeodomain Proteins; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics*; D011401:Promoter Regions, Genetic; D051381:Rats; D012045:Regulatory Sequences, Nucleic Acid; D014157:Transcription Factors; D000099161:Kcnj11 Channel
D000255:Adenosine Triphosphate; D004247:DNA; D017931:DNA Primers; D018398:Homeodomain Proteins; D007328:Insulin; D060850:LIM-Homeodomain Proteins; D009419:Nerve Tissue Proteins; D024661:Potassium Channels, Inwardly Rectifying; D014157:Transcription Factors; D000099161:Kcnj11 Channel; C063843:insulin gene enhancer binding protein Isl-1