Aberrant regulation of human intestinal proglucagon gene expression in the NCI-H716 cell line.
Despite interest in understanding glucagon-like peptide-1 (GLP-1) production, the factors important for GLP-1 biosynthesis remain poorly understood. We examined control of human proglucagon gene expression in NCI-H716 cells, a cell line that secretes GLP-1 in a regulated manner. Insulin, phorbol myristate acetate, or forskolin, known regulators of rodent proglucagon gene expression, had no effect, whereas sodium butyrate decreased levels of NCI-H716 proglucagon mRNA transcripts. The inhibitory effect of sodium butyrate was mimicked by trichostatin A but was not detected with sodium acetate or isobutyrate. The actions of butyrate were not diminished by the ERK1/2 inhibitor PD98059, p38 inhibitor SB203580, or soluble guanylate cyclase inhibitor LY83583 or following treatment of cells with KT5823, a selective inhibitor of cGMP-dependent protein kinase. NCI-H716 cells expressed multiple proglucagon gene transcription factors including isl-1, pax-6, pax-2, cdx-2/3, pax-4, hepatocyte nuclear factor (HNF)-3 alpha, HNF-3beta, HNF-3 gamma, and Nkx2.2. Nevertheless, the butyrate-dependent inhibition of proglucagon gene expression was not associated with coordinate changes in transcription factor expression and both the human and rat transfected proglucagon promoters were transcriptionally inactive in NCI-H716 cells. Hence, NCI-H716 cells may not be a physiologically optimal model for studies of human enteroendocrine proglucagon gene transcription.
Cao
Xiemin
X
Banting and Best Diabetes Centre, Toronto General Hospital, University of Toronto, Toronto, Canada M5G 2C4.
Flock
Grace
G
Choi
Caroline
C
Irwin
David M
DM
Drucker
Daniel J
DJ
D000230:Adenocarcinoma / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D002087:Butyrates / Q000494:pharmacology; D002430:Cecal Neoplasms / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D005786:Gene Expression Regulation / Q000502:physiology*; D005934:Glucagon / Q000235:genetics* / Q000378:metabolism; D052216:Glucagon-Like Peptide 1; D000090322:Homeobox Protein Nkx-2.2; D018398:Homeodomain Proteins; D006801:Humans; D007422:Intestines / Q000503:physiopathology*; D009687:Nuclear Proteins; D010446:Peptide Fragments / Q000378:metabolism; D052336:Proglucagon; D011498:Protein Precursors / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured
D002087:Butyrates; D000090322:Homeobox Protein Nkx-2.2; D018398:Homeodomain Proteins; C000715631:NKX2-2 protein, human; C000715628:Nkx2-2 protein, rat; D009687:Nuclear Proteins; D010446:Peptide Fragments; D011498:Protein Precursors; D014157:Transcription Factors; D052336:Proglucagon; D052216:Glucagon-Like Peptide 1; D005934:Glucagon