title: Pancreatic and duodenal homeobox-1 nuclear localization is regulated by glucose in dispersed rat islets but not in insulin-secreting cell lines.
abstract: The transcription factor Pancreatic and Duodenal Homeobox-1 (PDX-1) plays a major role in the development and function of pancreatic β-cells and its mutation results in diabetes. In adult β-cells, glucose stimulates transcription of the insulin gene in part by regulating PDX-1 expression, stability and activity. Glucose is also thought to modulate PDX-1 nuclear translocation but in vitro studies examining nucleo-cytoplasmic shuttling of endogenous or ectopically expressed PDX-1 in insulin-secreting cell lines have led to conflicting results. Here we show that endogenous PDX-1 undergoes translocation from the cytoplasm to the nucleus in response to glucose in dispersed rat islets but not in insulin-secreting MIN6, HIT-T15, or INS832/13 cells. Interestingly, however, we found that a PDX-1-GFP fusion protein can shuttle from the cytoplasm to the nucleus in response to glucose stimulation in HIT-T15 cells. Our results suggest that the regulation of endogenous PDX-1 sub-cellular localization by glucose is observed in primary islets and that care should be taken when interpreting data from insulin-secreting cell lines.
authors.affiliation: a Montreal Diabetes Research Center; CRCHUM ; Montreal , QC , Canada.
authors.forename: Meriem
authors.initials: M
authors.lastname: Semache
authors.forename: Julien
authors.initials: J
authors.lastname: Ghislain
authors.forename: Bader
authors.initials: B
authors.lastname: Zarrouki
authors.forename: Caroline
authors.initials: C
authors.lastname: Tremblay
authors.forename: Vincent
authors.initials: V
authors.lastname: Poitout
mesh_terms: D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology*; D018398:Homeodomain Proteins / Q000378:metabolism*; D007150:Immunohistochemistry; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D007515:Islets of Langerhans / Q000378:metabolism*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D015534:Trans-Activators / Q000378:metabolism*
chemical_list: D018398:Homeodomain Proteins; D015534:Trans-Activators; C084010:pancreatic and duodenal homeobox 1 protein; D005947:Glucose
keywords: ANOVA, analysis of variance; BSA, bovine serum albumin; DAPI, 4′, 6-diamidino-2-phenylindole; DMEM, dulbecco's modified eagle medium; EDTA, ethylenediaminetetraacetic acid; GFP, green fluorescent protein; HDAC, histone deacetylase; HIT-T15; INS832/13; KRBH, krebs ringer bicarbonate hepes; MIN6; MODY, maturity-onset diabetes of the young; PDX-1; PDX-1, pancreatic and duodenal homeobox-1; SEM, standard error of the mean; SUMO, small ubiquitin-like modifier; T2D, type 2 diabetes; ZDF, zucker diabetic fatty; glucose; glucose-stimulated insulin secretion; nucleo-cytoplasmic shuttling; pancreatic β cells