In nonexcitable cells, Ca²⁺ entry is mediated predominantly through the store depletion-dependent Ca²⁺ channels called store-operated Ca²⁺ (SOC) or Ca²⁺ release-activated Ca²⁺ channels. YM-58483, a pyrazole derivative, inhibited an anti-CD3 mAb-induced sustained Ca²⁺ influx in acute T cell leukemia, Jurkat cells. But it did not affect an anti-CD3 mAb-induced transient intracellular Ca²⁺ increase in Ca²⁺-free medium, nor anti-CD3 mAb-induced phosphorylation of phospholipase Cγ1. It was suggested that YM-58483 inhibited Ca²⁺ influx through SOC channels without affecting the TCR signal transduction cascade. Furthermore, YM-58483 inhibited thapsigargin-induced sustained Ca²⁺ influx with an IC₅₀ value of 100 nM without affecting membrane potential. YM-58483 inhibited by 30-fold the Ca²⁺ influx through SOC channels compared with voltage-operated Ca²⁺ channels, while econazole inhibited both SOC channels and voltage-operated Ca²⁺ channels with an equivalent range of IC₅₀ values. YM-58483 potently inhibited IL-2 production and NF-AT-driven promoter activity, but not AP-1-driven promoter activity in Jurkat cells. Moreover, this compound inhibited delayed-type hypersensitivity in mice with an ED₅₀ of 1.1 mg/kg. Therefore, we concluded that YM-58483 was a novel store-operated Ca²⁺ entry blocker and a potent immunomodulator, and could be useful for the treatment of autoimmune diseases and chronic inflammation. Furthermore, YM-58483 would be a candidate for the study of capacitative Ca²⁺ entry mechanisms through SOC/CRAC channels and for identification of putative Ca²⁺ channel genes.

3,5-Bis(trifluoromethyl)pyrazole derivative (BTP2) or N-[4-3, 5-bis(trifluromethyl)pyrazol-1-yl]-4-methyl-1,2,3-thiadiazole-5-carboxamide (YM-58483) is an immunosuppressive compound that potently inhibits both Ca²⁺ influx and interleukin-2 (IL-2) production in lymphocytes. We report here that BTP2 dosedependently enhances transient receptor potential melastatin 4 (TRPM4), a Ca²⁺-activated nonselective (CAN) cation channel that decreases Ca²⁺ influx by depolarizing lymphocytes. The effect of BTP2 on TRPM4 occurs at low nanomolar concentrations and is highly specific, because other ion channels in T lymphocytes are not significantly affected, and the major Ca²⁺ influx pathway in lymphocytes, I_CRAC, is blocked only at 100-fold higher concentrations. The efficacy of BTP2 in blocking IL-2 production is reduced approximately 100-fold when preventing TRPM4-mediated membrane depolarization, suggesting that the BTP2-mediated facilitation of TRPM4 channels represents the major mechanism for its immunosuppressive effect. Our results demonstrate that TRPM4 channels represent a previously unrecognized key element in lymphocyte Ca²⁺ signaling and that their facilitation by BTP2 supports cell membrane depolarization, which reduces the driving force for Ca²⁺ entry and ultimately causes the potent suppression of cytokine release.