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Role of Ca2+-activated K+ channels in human erythrocyte apoptosis.

Lang, Philipp A, Kaiser, Stefanie, Mysina, Svetlana, Wieder, Thomas, Lang, Florian and Huber, Stephan M (2003) Role of Ca2+-activated K+ channels in human erythrocyte apoptosis. American journal of physiology. Cell physiology, 285 (6). C1553-60. ISSN 0363-6143

Item Type: Article

Abstract

Exposure of erythrocytes to the Ca2+ ionophore ionomycin has recently been shown to induce cell shrinkage, cell membrane blebbing, and breakdown of phosphatidylserine asymmetry, all features typical of apoptosis of nucleated cells. Although breakdown of phosphatidylserine asymmetry is thought to result from activation of a Ca2+-sensitive scramblase, the mechanism and role of cell shrinkage have not been explored. The present study was performed to test whether ionomycin-induced activation of Ca2+-sensitive Gardos K+ channels and subsequent cell shrinkage participate in ionomycin-induced breakdown of phosphatidylserine asymmetry of human erythrocytes. According to on-cell patch-clamp experiments, ionomycin (1 microM) induces activation of inwardly rectifying K+-selective channels in the erythrocyte membrane. Fluorescence-activated cell sorter analysis reveals that ionomycin leads to a significant decrease of forward scatter, reflecting cell volume, an effect blunted by an increase of extracellular K+ concentration to 25 mM and exposure to the Gardos K+ channel blockers charybdotoxin (230 nM) and clotrimazole (5 microM). As reflected by annexin binding, breakdown of phosphatidylserine asymmetry is triggered by ionomycin, an effect again blunted, but not abolished, by an increase of extracellular K+ concentration and exposure to charybdotoxin (230 nM) and clotrimazole (5 microM). Similar to ionomycin, glucose depletion leads (within 55 h) to annexin binding of erythrocytes, an effect again partially reversed by an increase of extracellular K+ concentration and exposure to charybdotoxin. K-562 human erythroleukemia cells similarly respond to ionomycin with cell shrinkage and annexin binding, effects blunted by antisense, but not sense, oligonucleotides against the small-conductance Ca2+-activated K+ channel isoform hSK4 (KCNN4). The experiments disclose a novel functional role of Ca2+-sensitive K+ channels in erythrocytes, i.e., their participation in regulation of erythrocyte apoptosis.

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More Information

Depositing User: Svetlana Mysina

Identifiers

Item ID: 10018
ISSN: 0363-6143
URI: http://sure.sunderland.ac.uk/id/eprint/10018

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Catalogue record

Date Deposited: 08 Oct 2018 09:50
Last Modified: 09 Oct 2018 11:17

Contributors

Author: Philipp A Lang
Author: Stefanie Kaiser
Author: Svetlana Mysina
Author: Thomas Wieder
Author: Florian Lang
Author: Stephan M Huber

Subjects

Sciences > Biomedical Sciences

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