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Single Channel Properties and Regulated Expression of Ca2+ Release-Activated Ca2+ (CRAC) Channels in Human T Cells
Journal of Cell Biology
  • Alla F. Fomina
  • Christopher M. Fanger
  • J. Ashot Kozak, Wright State University - Main Campus
  • Michael D. Cahalan
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Publication Date
Although the crucial role of Ca2+ influx in lymphocyte activation has been well documented, little is known about the properties or expression levels of Ca2+ channels in normal human T lymphocytes. The use of Na+ as the permeant ion in divalent-free solution permitted Ca2+ release-activated Ca2+ (CRAC) channel activation, kinetic properties, and functional expression levels to be investigated with single channel resolution in resting and phytohemagglutinin (PHA)-activated human T cells. Passive Ca2+ store depletion resulted in the opening of 41-pS CRAC channels characterized by high open probabilities, voltage-dependent block by extracellular Ca2+ in the micromolar range, selective Ca2+ permeation in the millimolar range, and inactivation that depended upon intracellular Mg2+ ions. The number of CRAC channels per cell increased greatly from ∼15 in resting T cells to ∼140 in activated T cells. Treatment with the phorbol ester PMA also increased CRAC channel expression to ∼60 channels per cell, whereas the immunosuppressive drug cyclosporin A (1 μM) suppressed the PHA-induced increase in functional channel expression. Capacitative Ca2+ influx induced by thapsigargin was also significantly enhanced in activated T cells. We conclude that a surprisingly low number of CRAC channels are sufficient to mediate Ca2+ influx in human resting T cells, and that the expression of CRAC channels increases ∼10-fold during activation, resulting in enhanced Ca2+ signaling.

Copyright © 2000 The Rockefeller University Press.

Journal of Cell Biology, 150(6), pgs. 1435-1444, September 2000.

Citation Information
Alla F. Fomina, Christopher M. Fanger, J. Ashot Kozak and Michael D. Cahalan. "Single Channel Properties and Regulated Expression of Ca2+ Release-Activated Ca2+ (CRAC) Channels in Human T Cells" Journal of Cell Biology Vol. 150 Iss. 6 (2000) p. 1435 - 1444 ISSN: 0021-9525
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