en
Scientific article
Open access
English

Suppression of Pdx-1 perturbs proinsulin processing, insulin secretion and GLP-1 signalling in INS-1 cells

Published inDiabetologia, vol. 48, no. 4, p. 720-731
Collection
  • Open Access - Licence nationale Springer
Publication date2005
Abstract

AIMS/HYPOTHESIS: Mutations in genes encoding HNF-4alpha, HNF-1alpha and IPF-1/Pdx-1 are associated with, respectively, MODY subtypes-1, -3 and -4. Impaired glucose-stimulated insulin secretion is the common primary defect of these monogenic forms of diabetes. A regulatory circuit between these three transcription factors has also been suggested. We aimed to explore how Pdx-1 regulates beta cell function and gene expression patterns. METHODS: We studied two previously established INS-1 stable cell lines permitting inducible expression of, respectively, Pdx-1 and its dominant-negative mutant. We used HPLC for insulin processing, adenovirally encoded aequorin for cytosolic [Ca2+], and transient transfection of human growth hormone or patch-clamp capacitance recordings to monitor exocytosis. RESULTS: Induction of DN-Pdx-1 resulted in defective glucose-stimulated and K+-depolarisation-induced insulin secretion in INS-1 cells, while overexpression of Pdx-1 had no effect. We found that DN-Pdx-1 caused down-regulation of fibroblast growth factor receptor 1 (FGFR1), and consequently prohormone convertases (PC-1/3 and -2). As a result, DN-Pdx-1 severely impaired proinsulin processing. In addition, induction of Pdx-1 suppressed the expression of glucagon-like peptide 1 receptor (GLP-1R), which resulted in marked reduction of both basal and GLP-1 agonist exendin-4-stimulated cellular cAMP levels. Induction of DN-Pdx-1 did not affect glucokinase activity, glycolysis, mitochondrial metabolism or ATP generation. The K+-induced cytosolic [Ca2+] rise and Ca2+-evoked exocytosis (membrane capacitance) were not abrogated. CONCLUSIONS/INTERPRETATION: The severely impaired proinsulin processing combined with decreased GLP-1R expression and cellular cAMP content, rather than metabolic defects or altered exocytosis, may contribute to the beta cell dysfunction induced by Pdx-1 deficiency.

Keywords
  • Adenosine Triphosphate/metabolism
  • Animals
  • Calcium Signaling/physiology
  • Cell Line, Tumor
  • Cyclic AMP/metabolism
  • Dose-Response Relationship, Drug
  • Doxycycline/pharmacology
  • Exocytosis/physiology
  • Gene Expression/drug effects/genetics
  • Gene Expression Regulation, Neoplastic/drug effects
  • Glucokinase/genetics
  • Glucose/metabolism/pharmacology
  • Glycolysis
  • Homeodomain Proteins/genetics/metabolism/ physiology
  • Human Growth Hormone/genetics/secretion
  • Insulin/ secretion
  • Islets of Langerhans/drug effects/metabolism
  • Mitochondria/metabolism
  • Mutation
  • Proinsulin/ metabolism
  • Proprotein Convertases/genetics
  • RNA, Messenger/genetics/metabolism
  • Rats
  • Receptor Protein-Tyrosine Kinases/genetics
  • Receptor, Fibroblast Growth Factor, Type 1
  • Receptors, Fibroblast Growth Factor/genetics
  • Receptors, Glucagon/genetics/ physiology
  • Signal Transduction/ physiology
  • Time Factors
  • Trans-Activators/genetics/metabolism/ physiology
  • Transfection
Citation (ISO format)
WANG, Haiyan et al. Suppression of Pdx-1 perturbs proinsulin processing, insulin secretion and GLP-1 signalling in INS-1 cells. In: Diabetologia, 2005, vol. 48, n° 4, p. 720–731. doi: 10.1007/s00125-005-1692-8
Main files (1)
Article (Published version)
accessLevelPublic
Identifiers
ISSN of the journal0012-186X
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137downloads

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