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Expression and function of pancreatic beta-cell delayed rectifier K+ channels. Role in stimulus-secretion coupling
M W Roe1, J F Worley, A A Mittal
1Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA. l-philipson@uchicago.edu
The Journal of Biological Chemistry
|December 13, 1996
Summary
Delayed rectifier potassium channels, including Kv2.1, regulate insulin secretion by controlling calcium oscillations in pancreatic beta cells. Blocking these channels potentiates insulin release, highlighting their role in stimulus-secretion coupling.
Area of Science:
- Cellular Electrophysiology
- Endocrinology
- Ion Channel Biology
Background:
- Voltage-dependent delayed rectifier K+ channels are crucial for cellular electrical activity and secretion.
- Their specific roles in pancreatic beta-cells and glucose-stimulated insulin secretion remain incompletely understood.
Purpose of the Study:
- To investigate the expression and function of delayed rectifier K+ channels in pancreatic beta-cells.
- To determine the impact of these channels on glucose-stimulated insulin secretion and intracellular calcium dynamics.
Main Methods:
- Utilized transgenically derived insulinoma cells (betaTC3-neo) and primary rodent beta-cells.
- Employed reverse-transcription polymerase chain reaction (RT-PCR) and immunoblotting for gene expression analysis.
- Performed whole-cell patch clamp electrophysiology and fura-2 microspectrofluorimetry to assess ion currents and intracellular calcium ([Ca2+]i).
Main Results:
- Detected expression of Kv2.1 and Kv3.2 delayed rectifier K+ channel transcripts in betaTC3-neo cells and rodent beta-cells.
- Observed TEA-sensitive delayed rectifier K+ currents, correlating with Kv2.1 expression.
- Demonstrated that tetraethylammonium (TEA) blockade of these channels induced [Ca2+]i oscillations and potentiated insulin secretion in the presence of glucose.
Conclusions:
- Specific delayed rectifier K+ channels in beta-cells can suppress stimulus-secretion coupling by modulating membrane potential and [Ca2+]i oscillations.
- These findings implicate previously uncharacterized beta-cell delayed rectifier K+ channels in regulating membrane repolarization, [Ca2+]i, and insulin secretion.