Characterization of voltage- and Ca2+ -activated K+ channels in rat dorsal root ganglion neurons
Characterization of voltage- and Ca2+ -activated K+ channels in rat dorsal root ganglion neurons
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DOI：
10.1002/jcp.21007
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发表时间：
2007-08-01
影响因子：
5.6
通讯作者：
Xu, Tao
中科院分区：
文献类型：
--
作者：
Li, Wei;Gao, Shang-Bang;Xu, Tao
与成孔 Slo I α 亚基相关的辅助 P 亚基在调节大电导、电压和 Ca2+ 激活的 K+ 通道（通常称为 BK 通道）的功能特性中发挥着重要作用。尽管非失活和失活 BK 通道均被认为受 P 亚基（β 1、132、β 3 或 β 4）调节，但天然细胞中失活 BK 通道的分子决定因素尚未得到广泛证实。在这项研究中，通过 RT-PCR，r beta 2（但不是 r beta 3 亚基）被鉴定为大鼠腰椎 L4-6 背根神经节 (DRG) 的分子成分，负责灭活小感觉神经元中大电导 Ca2+ 依赖性 K+ 电流 (BKi 电流)。从全细胞和内向外斑块获得的天然 BKi 电流的特性与爪蟾卵母细胞中共表达 mSlo I α 和 h β 2 亚基产生的失活 BK 通道非常相似。细胞内应用 0.5 mg/ml 胰蛋白酶可消除 BKi 通道的失活，而 BK 通道的特异性阻断剂 Charybdotoxin (ChTX) 和 iberiotoxin (IbTX) 可抑制这些 BKi 电流。从内向外斑片导出的单 BKi 通道电流表明，一个 BKi 通道包含三个 r beta 2 亚基（平均），在 160 K+ 对称记录条件下，单通道电导约为 217 pS。 100 nM IbTX 阻断 BKi 通道可增强放电频率、加宽动作电位波形并减少后超极化。我们认为小直径 DRG 感觉神经元中的 BKi 通道可能在调节中枢神经系统 (CNS) 伤害性输入方面发挥重要作用。
Auxiliary P-subunits associated with pore-forming Slo I alpha-subunits play an essential role in regulating functional properties of large-conductance, voltage- and Ca2+-activated K+ channels commonly termed BK channels. Even though both noninactivating and inactivating BK channels are thought to be regulated by P-subunits (beta 1, 132, beta 3, or beta 4), the molecular determinants underlying inactivating BK channels in native cells have not been extensively demonstrated. In this study, r beta 2 (but not r beta 3-subunit) was identified as a molecular component in rat lumbar L4-6 dorsal root ganglia (DRG) by RT-PCR responsible for inactivating large-conductance Ca2+-dependent K+ currents (BKi currents) in small sensory neurons. The properties of native BKi currents obtained from both whole-cell and inside-out patches are very similar to inactivating BK channels produced by co-expressing mSlo I alpha- and h beta 2-subunits in Xenopus oocytes. Intracellular application of 0.5 mg/ml trypsin removes inactivation of BKi channels, and the specific blockers of BK channels, charybdotoxin (ChTX) and iberiotoxin (IbTX), inhibit these BKi currents. Single BKi channel currents derived from inside-out patches revealed that one BKi channel contained three r beta 2-subunits (on average), with a single-channel conductance about 217 pS under 160 K+ symmetrical recording conditions. Blockade of BKi channels by 100 nM IbTX augmented firing frequency, broadened action potential waveform and reduced afterhyperpolarization. We propose that the BKi channels in small diameter DRG sensory neurons might play an important role in regulating nociceptive input to the central nervous system (CNS).