Calcium oscillations in T-cells: mechanisms and consequences for gene expression

[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.