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

Wang, Haiyan; Iezzi, M.; Theander, Sten; Antinozzi, P. A.; Gauthier, B. R.; Halban, Philippe A.; Wollheim, Claes

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Title		Suppression of Pdx-1 perturbs proinsulin processing, insulin secretion and GLP-1 signalling in INS-1 cells
Authors		Wang, Haiyan Iezzi, M. Theander, Sten Antinozzi, P. A. Gauthier, B. R. Halban, Philippe A. Wollheim, Claes
Published in		Diabetologia. 2005, vol. 48, no. 4, p. 720-731
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
Identifiers		DOI: 10.1007/s00125-005-1692-8 PMID: 15756539
Full text		Article - Limited access to UNIGE Other version: http://www.springerlink.com/content/w42kh670173v3360/fulltext.pdf
Structures		Faculté de médecine / Section de médecine clinique / Département de médecine interne des spécialités
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. https://archive-ouverte.unige.ch/unige:9086