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Intracellular diadenosine polyphosphates: a novel second messenger in stimulus-secretion coupling
F Martín1, J Pintor, J M Rovira
1Department of Science and Technology and Institute of Bioengineering, Campus de San Juan, Miguel Hernandez University, Alicante, Spain.
Summary
Stimulatory glucose increases diadenosine polyphosphates (ApnA) in pancreatic beta-cells, which block KATP channels. Nutrient metabolism regulates ApnA synthesis, revealing a new regulator of beta-cell function.
Area of Science:
- Cellular metabolism
- Ion channel regulation
- Pancreatic beta-cell function
Background:
- Glucose stimulates pancreatic beta-cells to release insulin.
- ATP-sensitive potassium (KATP) channels are crucial regulators of insulin secretion.
- Diadenosine polyphosphates (ApnA) are implicated in cellular signaling.
Purpose of the Study:
- To investigate the metabolic pathways of ApnA synthesis in pancreatic beta-cells.
- To elucidate the mechanism by which ApnA inhibit KATP channels.
- To determine the role of ApnA in glucose-stimulated insulin secretion.
Main Methods:
- High-performance liquid chromatography (HPLC) to measure cytosolic ApnA concentrations.
- Patch clamp electrophysiology to study KATP channel activity.
- Metabolic inhibitors to probe substrate utilization and ApnA synthesis pathways.
Main Results:
- Glucose and other fuel secretagogues (leucine, 2-ketoisocaproate) significantly increase cytosolic ApnA levels in a time- and glucose-dependent manner.
- Inhibition of glycolysis or the Krebs cycle reduces glucose-induced ApnA synthesis.
- ApnA inhibit KATP channels similarly to ATP but exhibit distinct functional properties, such as not restoring channel activity after rundown.
- ApnA and ATP do not compete for the same binding site on KATP channels.
Conclusions:
- Nutrient metabolism, via pyrophosphatase activation, is essential for ApnA synthesis in beta-cells.
- ApnA represent a novel, ATP-independent metabolic regulator of KATP channel activity.
- ApnA play a significant role in beta-cell function, comparable to ATP.