UNIGE document Scientific Article
previous document  unige:35183  next document
add to browser collection
Title

GAD65-mediated glutamate decarboxylation reduces glucose-stimulated insulin secretion in pancreatic beta cells

Authors
Hegardt, F G
Published in Journal of Biological Chemistry. 2001, vol. 276, no. 39, p. 36391-6
Abstract Mitochondrial metabolism plays a pivotal role in the pancreatic beta cell by generating signals that couple glucose sensing to insulin secretion. We have demonstrated previously that mitochondrially derived glutamate participates directly in the stimulation of insulin exocytosis. The aim of the present study was to impose altered cellular glutamate levels by overexpression of glutamate decarboxylase (GAD) to repress elevation of cytosolic glutamate. INS-1E cells infected with a recombinant adenovirus vector encoding GAD65 showed efficient overexpression of the GAD protein with a parallel increase in enzyme activity. In control cells glutamate levels were slightly increased by 7.5 mm glucose (1.4-fold) compared with the effect at 15 mm (2.3-fold) versus basal 2.5 mm glucose. Upon GAD overexpression, glutamate concentrations were no longer elevated by 15 mm glucose as compared with controls (-40%). Insulin secretion was stimulated in control cells by glucose at 7.5 mm (2.5-fold) and more efficiently at 15 mm (5.2-fold). INS-1E cells overexpressing GAD exhibited impaired insulin secretion on stimulation with 15 mm glucose (-37%). The secretory response to 30 mm KCl, used to raise cytosolic Ca(2+) levels, was unaffected. Similar results were obtained in perifused rat pancreatic islets following adenovirus transduction. This GAD65-mediated glutamate decarboxylation correlating with impaired glucose-induced insulin secretion is compatible with a role for glutamate as a glucose-derived factor participating in insulin exocytosis.
Keywords Adenosine Triphosphate/metabolismAdenoviridae/geneticsAnimalsCalcium/metabolismCells, CulturedCytosol/metabolismExocytosisGlucose/metabolismGlutamate Decarboxylase/metabolismGlutamates/metabolismGlutamic Acid/metabolismHumansImmunoblottingInsulin/metabolism/secretionIslets of Langerhans/cytology/metabolismIsoenzymes/metabolismMembrane PotentialsMicroscopy, FluorescenceMitochondria/metabolismProtein BindingRatsRecombinant Proteins/metabolismTime FactorsTransduction, GeneticTumor Cells, Cultured
Identifiers
PMID: 11473118
Full text
Article (Published version) (161 Kb) - public document Free access
Structures
Citation
(ISO format)
RUBI, Blanca et al. GAD65-mediated glutamate decarboxylation reduces glucose-stimulated insulin secretion in pancreatic beta cells. In: Journal of Biological Chemistry, 2001, vol. 276, n° 39, p. 36391-6. https://archive-ouverte.unige.ch/unige:35183

290 hits

104 downloads

Update

Deposited on : 2014-04-01

Export document
Format :
Citation style :