[Ca2+]i (intracellular Ca2+ concentration) oscillations play a central role in the activation of T-lymphocytes by antigen. Oscillations in T-cells are absolutely dependent on Ca2+ influx through store-operated CRAC channels (Ca2+-release-activated Ca2+ channels), and evidence suggests that they arise from delayed interactions between these channels and Ca2+ stores. Their potential functions have been explored by creating controlled [Ca2+]i oscillations with pulses of Ca2+ entry or pulses of Ins(1,4,5)P3. Oscillations enhance both the efficiency and specificity of signalling through the Ca2+-dependent transcription factors nuclear factor of activated T-cells (NFAT), Oct/Oap and nuclear factor κB (NFκB) in ways that are consistent with each factor's Ca2+ dependence and kinetics of activation and deactivation. These studies show how [Ca2+]i oscillations may enhance signalling to the nucleus, and suggest a possible cellular mechanism for extracting information encoded in oscillation frequency.

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