Expression and Function of Pancreatic β-Cell Delayed Rectifier K+ Channels
| Autor: | Robert J. Mertz, Nathaniel T. Blair, W. Ronald Shehee, Sam M. Witherspoon, Michael W. Roe, Jennings F. Worley, Andrey V. Kuznetsov, M S McIntyre, Anshu A. Mittal, Mary E. Lancaster, Sarmila DasGupta, Iain D. Dukes, Louis H. Philipson |
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| Rok vydání: | 1996 |
| Předmět: |
Membrane potential
medicine.medical_specialty Tetraethylammonium Pancreatic islets Cell Biology Biology medicine.disease Biochemistry Cell biology chemistry.chemical_compound Membrane repolarization Endocrinology medicine.anatomical_structure chemistry Internal medicine medicine Secretion Patch clamp Molecular Biology Insulinoma Intracellular |
| Zdroj: | Journal of Biological Chemistry. 271:32241-32246 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.271.50.32241 |
| Popis: | Voltage-dependent delayed rectifier K+ channels regulate aspects of both stimulus-secretion and excitation-contraction coupling, but assigning specific roles to these channels has proved problematic. Using transgenically derived insulinoma cells (βTC3-neo) and β-cells purified from rodent pancreatic islets of Langerhans, we studied the expression and role of delayed rectifiers in glucose-stimulated insulin secretion. Using reverse-transcription polymerase chain reaction methods to amplify all known candidate delayed rectifier transcripts, the expression of the K+ channel gene Kv2.1 in βTC3-neo insulinoma cells and purified rodent pancreatic β-cells was detected and confirmed by immunoblotting in the insulinoma cells. βTC3-neo cells were also found to express a related K+ channel, Kv3.2. Whole-cell patch clamp demonstrated the presence of delayed rectifier K+ currents inhibited by tetraethylammonium (TEA) and 4-aminopyridine, with similar Kd values to that of Kv2.1, correlating delayed rectifier gene expression with the K+ currents. The effect of these blockers on intracellular Ca2+ concentration ([Ca2+]i) was studied with fura-2 microspectrofluorimetry and imaging techniques. In the absence of glucose, exposure to TEA (1-20 mM) had minimal effects on βTC3-neo or rodent islet [Ca2+]i, but in the presence of glucose, TEA activated large amplitude [Ca2+]i oscillations. In the insulinoma cells the TEA-induced [Ca2+]i oscillations were driven by synchronous oscillations in membrane potential, resulting in a 4-fold potentiation of insulin secretion. Activation of specific delayed rectifier K+ channels can therefore suppress stimulus-secretion coupling by damping oscillations in membrane potential and [Ca2+]i and thereby regulate secretion. These studies implicate previously uncharacterized β-cell delayed rectifier K+ channels in the regulation of membrane repolarization, [Ca2+]i, and insulin secretion. |
| Databáze: | OpenAIRE |
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