Differential pathways for calcium influx activated by concanavalin A and CD3 stimulation in Jurkat T cells

Sustained increase in [Ca(2+)](c) (Δ[Ca(2+)](c)) is a critical early signal from T-cell receptor (TCR/CD3). In general, Ca(2+)-release activated Ca(2+) channels (CRAC) are responsible for the Ca(2+) influx and Δ[Ca(2+)](c) after TCR/CD3 stimulation. However, T cells also express Ca(2+)-permeable nonselective cation channels such as TRPM2 and TRPC. Gd(3+) is a relatively selective blocker for CRAC at micromolar concentrations. Here, Jurkat T cells were used to investigate the Gd(3+)-resistant Ca(2+) influx (Δ[Ca(2+)](c,Gd)) induced by concanavalin A (ConA, 1 μg/ml), a widely used mitogenic agent for T cells, or by anti-CD3 Ab (αCD3). αCD3-induced Δ[Ca(2+)](c) was partly (~60%) inhibited by 1 μM Gd(3+) while thapsigargin-induced Δ[Ca(2+)] was almost completely abolished. ConA-induced Δ[Ca(2+)] was mostly inhibited by 1 μM Gd(3+) during the early phase (<30 s of ConA application) and became resistant during the late phase (>2 min). Induction of Δ[Ca(2+)](c,Gd) by αCD3 and ConA was inhibited by 2-aminoethoxydiphenyl borate (2-APB) and by N-(p-amylcinnamoyl) anthranilic acid, indicating that TRPM2 and TRPC are involved in this process. Treatment with Pyr-3, a TRPC3-specific inhibitor, potently suppressed Δ[Ca(2+)](c,Gd) by αCD3 (IC(50), 0.16 μM). Patch clamp experiments demonstrated that the TRPM2 channels were activated by ConA, and the TRPC-like channels were activated by αCD3. Our present study suggests that TRPM2 and TRPC3 are activated by ConA and TCR/CD3, respectively, in Jurkat T cells and are responsible for the induction of Δ[Ca(2+)](c,Gd).