Voltage-activated proton currents in human lymphocytes

• Published in: The Journal of physiology Vol. 545; no. 1; pp. 93 - 105
• Main Authors: Schilling, Tom, Gratopp, Alexander, DeCoursey, Thomas E., Eder, Claudia
• Format: Journal Article
• Language: English
• Published: Oxford, UK The Physiological Society 15-11-2002; Blackwell Publishing Ltd; Blackwell Science Inc
• Subjects: B-Lymphocytes - drug effects; B-Lymphocytes - metabolism; Calcium - physiology; Electric Conductivity; Electrophysiology; Humans; Hydrogen-Ion Concentration; Ion Channels - physiology; Jurkat Cells; Lymphocytes - metabolism; Original; Permeability; Protons; T-Lymphocytes - drug effects; T-Lymphocytes - metabolism; Tetradecanoylphorbol Acetate - pharmacology; Time Factors
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/jphysiol.2002.028878

Voltage-activated proton currents are reported for the first time in human peripheral blood T and B lymphocytes and in the
human leukaemic T cell line Jurkat E6-1. The properties of H + currents studied using tight-seal voltage-clamp recording techniques were similar in all cells. Changing the pH gradient
by one unit caused a 47 mV shift in the reversal potential, demonstrating high selectivity of the channels for protons. H + current activation upon membrane depolarisation had a sigmoidal time course that could be fitted by a single exponential
function after a brief delay. Increasing pH o shifted the activation threshold to more negative potentials, and increased both the H + current amplitude and the rate of activation. In lymphocytes studied at pH i 6.0, the activation threshold was more negative and the H + current density was three times larger than at pH i 7.0. Increasing the intracellular Ca 2+ concentration to 1 μ m did not change H + current amplitude or kinetics detectably. Extracellularly applied Zn 2+ and Cd 2+ inhibited proton currents, slowing activation and shifting the voltage–activation curve to more positive potentials. The
H + current amplitude was 100 times larger in CD19+ B lymphocytes and in Jurkat E6-1 cells than in CD3+ T lymphocytes. Following
stimulation with the phorbol ester PMA, the H + current density in peripheral blood T lymphocytes and Jurkat T cells increased. In contrast, the H + current density of phorbol ester (PMA)-stimulated B lymphocytes was reduced and activation became slower. The pattern of
expression of H + channels in lymphocytes appears well suited to their proposed role of charge compensation during the respiratory burst.