文摘
Sustained increase in [Ca2+]c (Δ[Ca2+]c) is a critical early signal from T-cell receptor (TCR/CD3). In general, Ca2+-release activated Ca2+ channels (CRAC) are responsible for the Ca2+ influx and Δ[Ca2+]c after TCR/CD3 stimulation. However, T cells also express Ca2+-permeable nonselective cation channels such as TRPM2 and TRPC. Gd3+ is a relatively selective blocker for CRAC at micromolar concentrations. Here, Jurkat T cells were used to investigate the Gd3+-resistant Ca2+ influx (Δ[Ca2+]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[Ca2+]c was partly (~60%) inhibited by 1?μM Gd3+ while thapsigargin-induced Δ[Ca2+] was almost completely abolished. ConA-induced Δ[Ca2+] was mostly inhibited by 1?μM Gd3+ during the early phase (<30?s of ConA application) and became resistant during the late phase (>2?min). Induction of Δ[Ca2+]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[Ca2+]c,Gd by αCD3 (IC50, 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[Ca2+]c,Gd.