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Potassium and Calcium Channels in Lymphocytes

Potassium and Calcium Channels in Lymphocytes Over the past decade, a variety of ion channels have been identified and characterized in lymphocytes by use of the patch-clamp technique. This review discusses biophysical and regulatory aspects of lymphocyte potassium and calcium channels with the aim of understanding the role of these channels in lymphocyte functions. Lymphocytes express both voltage-dependent potassium K(V) channels and calcium-activated potassium K(Ca) channels, and each is upregulated as cells progress toward division following mitogenic stimulation. The genes encoding two K(V) channels, Kv1.3 (type n ) and Kv3.1 (type l ), have cloned. Mutational analysis is revealing functionally important regions of these channel proteins. Exogenous expression studies and the use of highly specific channel blockers have helped to establish the roles of type n K(V) channels sustaining the resting membrane potential, in regulating cell volume, and in enabling lymphocyte activation. Blockade of K(V) and K(Ca) channels effectively inhibits the antigen-driven activation of lymphocytes, probably by inducing membraned epolarization and thereby diminishing calcium influx. A prolonged rise in intracellular calcium ( Ca 2+ i ) is a required signal for lymphocyte activation by antigen or mitogens. Single-cell fluorescence measurements have revealed underlying Ca 2+ i oscillations that are linked closely to the opening and closing of Ca 2+ and K + channels. Sustained Ca 2+ signaling and oscillations depend absolutely on plasma-membrane Ca 2+ channels that are activated by the depletion of intracellular calcium stores. Under physiological conditions these channels open as a consequence of store depletion induced by inositol 1,4,5-trisphosphate (IP 3 ), but they can also be activated experimentally by several agents that empty the stores without generating IP 3 , such as the microsomal Ca 2+ -ATPase inhibitor thapsigargin. The intricate causal relationships among ion channels, membrane potential, Ca 2+ i , and lymphokine gene expression can now be pursued at the single-cell level with patch-clamp recording, calcium-dependent dyes, reporter genes, and fluorescence video techniques. These approaches will help to clarify the essential roles of ion channels in the molecular pathways subserving activation and other lymphocyte behaviors. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Annual Review of Immunology Annual Reviews

Potassium and Calcium Channels in Lymphocytes

Annual Review of Immunology , Volume 13 (1) – Apr 1, 1995

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Publisher
Annual Reviews
Copyright
Copyright 1995 Annual Reviews. All rights reserved
Subject
Review Articles
ISSN
0732-0582
eISSN
1545-3278
DOI
10.1146/annurev.iy.13.040195.003203
pmid
7612237
Publisher site
See Article on Publisher Site

Abstract

Over the past decade, a variety of ion channels have been identified and characterized in lymphocytes by use of the patch-clamp technique. This review discusses biophysical and regulatory aspects of lymphocyte potassium and calcium channels with the aim of understanding the role of these channels in lymphocyte functions. Lymphocytes express both voltage-dependent potassium K(V) channels and calcium-activated potassium K(Ca) channels, and each is upregulated as cells progress toward division following mitogenic stimulation. The genes encoding two K(V) channels, Kv1.3 (type n ) and Kv3.1 (type l ), have cloned. Mutational analysis is revealing functionally important regions of these channel proteins. Exogenous expression studies and the use of highly specific channel blockers have helped to establish the roles of type n K(V) channels sustaining the resting membrane potential, in regulating cell volume, and in enabling lymphocyte activation. Blockade of K(V) and K(Ca) channels effectively inhibits the antigen-driven activation of lymphocytes, probably by inducing membraned epolarization and thereby diminishing calcium influx. A prolonged rise in intracellular calcium ( Ca 2+ i ) is a required signal for lymphocyte activation by antigen or mitogens. Single-cell fluorescence measurements have revealed underlying Ca 2+ i oscillations that are linked closely to the opening and closing of Ca 2+ and K + channels. Sustained Ca 2+ signaling and oscillations depend absolutely on plasma-membrane Ca 2+ channels that are activated by the depletion of intracellular calcium stores. Under physiological conditions these channels open as a consequence of store depletion induced by inositol 1,4,5-trisphosphate (IP 3 ), but they can also be activated experimentally by several agents that empty the stores without generating IP 3 , such as the microsomal Ca 2+ -ATPase inhibitor thapsigargin. The intricate causal relationships among ion channels, membrane potential, Ca 2+ i , and lymphokine gene expression can now be pursued at the single-cell level with patch-clamp recording, calcium-dependent dyes, reporter genes, and fluorescence video techniques. These approaches will help to clarify the essential roles of ion channels in the molecular pathways subserving activation and other lymphocyte behaviors.

Journal

Annual Review of ImmunologyAnnual Reviews

Published: Apr 1, 1995

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