Highly thermosensitive Ca ²⁺ dynamics in a HeLa cell through IP ₃ receptors

Intracellular Ca ²⁺ distribution and its dynamics are essential for various cellular functions. We show with single HeLa cells that a microscopic heat pulse induces Ca ²⁺ uptake into intracellular stores during heating and Ca ²⁺ release from them at the onset of recooling, and the overshoot of Ca ²⁺ release occurs above the critical value of a temperature change, which decreases from 1.5 to 0.2 °C on increasing the experimental temperature from 22 to 37 °C. This highly thermosensitive Ca ²⁺ dynamics is probably attributable to the altered balance between Ca ²⁺ uptake by endoplasmic reticulum Ca ²⁺-ATPases and Ca ²⁺ release via inositol 1,4,5-trisphosphate receptors. These results suggest that Ca ²⁺ signaling is extremely sensitive to temperature changes, especially around body temperature, in cells expressing inositol 1,4,5-trisphosphate receptors.