Effects of CRAC Channel on Spatiotemporal Ca²⁺ Patterns in T Cells

A reaction-diffusion model is built to investigate the temporal and spatial patterns of cytoplasmic Ca²⁺ dynamics under the effects of Ca²⁺-release activated Ca²⁺ (CRAC) channels in T cells. Simulation results show a strong dependence of the modulation mode of Ca²⁺ oscillation and dynamic patterns of Ca²⁺ wave on the influx rate through the CRAC channel (k_soc). When k_soc is small, cytoplasmic Ca²⁺ is modulated as a frequency-modulation (FM) signal, whereas it shows an amplitude modulation (AM) mode after k_soc passes through a critical value. The heterogeneity in spatial Ca²⁺ distribution is mostly arising from the influx through CRAC channels in both FM and AM modes. During each Ca²⁺ spike, a more sustained cytoplasmic Ca²⁺ gradient is maintained in the AM mode rather than in the FM mode.