Rader R K, Kahn L E, Anderson G D, Martin C L, Chinn K S, Gregory S A
Department of Protein Biochemistry, G. D. Searle & Company, St. Louis, MO 63198, USA.
J Immunol. 1996 Feb 15;156(4):1425-30.
Membrane potential (Vm) is tightly controlled in T cells through the regulated flux of ions across the plasma membrane. To investigate the functional role of voltage-dependent (Kv) and calcium-activated (KCa) potassium channels in T cell activation, we compared the effects of two K+ channel blockers, namely kaliotoxin (KTX) and charybdotoxin (CHTX), on Vm, calcium influx, and cell proliferation. KTX potently inhibited Kv (ID50 = 3 nM) but not KCa (ID50 = 5 microM) currents in T cells. Resting T cells exposed to KTX (300 nM) depolarized from -56 mV to -50 mV. KTX had no effect on the transient membrane hyperpolarization that characteristically follows receptor-mediated T cell stimulation. However, T cells stimulated in the presence of KTX subsequently depolarized to -40 mV. KTX also reduced the steady state intracellular free calcium concentration ([Ca2+]i) in stimulated cells by 19% and inhibited T cell proliferation by 35%. CHTX potently inhibited both Kv and KCa currents (ID50 = approximately 1 nM). CHTX (300 nM) depolarized resting T cells to -48 mV, equivalent to the effect observed for KTX. In stimulated T cells, 300 nM CHTX completely blocked the induced hyperpolarization and subsequently depolarized the cells to -21 mV. These effects were associated with a 45% reduction in peak [Ca2+]i, a 60% decrease in steady state [Ca2+]i, and 63% inhibition of T cell proliferation. These results suggest that both Kv and KCa conductances contribute to the underlying mechanisms of T cell activation.
膜电位（Vm）在T细胞中通过离子跨质膜的调节通量受到严格控制。为了研究电压依赖性（Kv）和钙激活（KCa）钾通道在T细胞活化中的功能作用，我们比较了两种钾通道阻滞剂，即卡利毒素（KTX）和蝎毒素（CHTX）对Vm、钙内流和细胞增殖的影响。KTX能有效抑制T细胞中的Kv电流（半数抑制浓度ID50 = 3 nM），但对KCa电流无抑制作用（ID50 = 5 μM）。暴露于KTX（300 nM）的静息T细胞从-56 mV去极化至-50 mV。KTX对受体介导的T细胞刺激后典型出现的短暂膜超极化没有影响。然而，在KTX存在下刺激的T细胞随后去极化至-40 mV。KTX还使受刺激细胞中的稳态细胞内游离钙浓度（[Ca2+]i）降低了19%，并抑制T细胞增殖35%。CHTX能有效抑制Kv和KCa电流（ID50约为1 nM）。CHTX（300 nM）使静息T细胞去极化至-48 mV，与KTX观察到的效果相当。在受刺激的T细胞中，300 nM CHTX完全阻断了诱导的超极化，并随后使细胞去极化至-21 mV。这些效应与峰值[Ca2+]i降低45%、稳态[Ca2+]i降低60%以及T细胞增殖抑制63%相关。这些结果表明，Kv和KCa电导都参与了T细胞活化的潜在机制。
