Glutaredoxin-1 mediates NADPH-dependent stimulation of calcium-dependent insulin secretion.
Forskningsoutput: Tidskriftsbidrag › Artikel i vetenskaplig tidskrift
Nicotinamide adenine dinucleotide phosphate (NADPH) enhances Ca(2+)-induced exocytosis in pancreatic beta-cells, an effect suggested to involve the cytosolic redox protein glutaredoxin-1 (GRX-1). We here detail the role of GRX-1 in NADPH-stimulated beta-cell exocytosis and glucose-stimulated insulin secretion. Silencing of GRX-1 by RNA interference reduced glucose-stimulated insulin secretion in both clonal INS-1 832/13 cells and primary rat islets. GRX-1 silencing did not affect cell viability or the intra-cellular redox environment, suggesting that GRX-1 regulates the exocytotic machinery by a local action. By contrast, knockdown of the related protein thioredoxin-1 (TRX-1) was ineffective. Confocal immunocytochemistry revealed that GRX-1 locates to the cell periphery, whereas TRX-1 expression is uniform. These data suggest that the distinct subcellular localizations of TRX-1 and GRX-1 result in differences in substrate specificities and actions on insulin secretion. Single-cell exocytosis was likewise suppressed by GRX-1 knockdown in both rat beta-cells and clonal 832/13 cells, whereas after overexpression exocytosis increased by approximately 40%. Intracellular addition of NADPH (0.1 mM) stimulated Ca(2+)-evoked exocytosis in both cell types. Interestingly, the stimulatory action of NADPH on the exocytotic machinery coincided with a approximately 30% inhibition in whole-cell Ca(2+) currents. After GRX-1 silencing, NADPH failed to amplify insulin release, but still inhibited Ca(2+) currents in 832/13 cells. In conclusion, NADPH stimulates the exocytotic machinery in pancreatic beta-cells. This effect is mediated by the NADPH acceptor protein GRX-1 by a local redox reaction that accelerates beta-cell exocytosis and, in turn, insulin secretion.
|Enheter & grupper|
Ämnesklassifikation (UKÄ) – OBLIGATORISK
|Status||Published - 2009|
|Peer review utförd||Ja|
New aspects of voltage-gated calcium channel regulation in pancreatic beta-cells - Relevance for insulin release and type 2 diabetesThomas Reinbothe, 2011, Department of Clinical Sciences, Lund University. 154 s.
Forskningsoutput: Avhandling › Doktorsavhandling (sammanläggning)