Molecular identification of a component of delayed rectifier current in gastrointestinal smooth muscles
Molecular identification of a component of delayed rectifier current in gastrointestinal smooth muscles
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DOI：
10.1152/ajpgi.1998.274.5.g901
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发表时间：
1998-05-01
影响因子：
4.5
通讯作者：
Horowitz, B
中科院分区：
文献类型：
--
作者：
Schmalz, F;Kinsella, J;Horowitz, B
Kv2.2与果蝇电压门控性钾通道的Shab家族同源，是从人和犬结肠环状平滑肌来源的mRNA中分离得到的。对从组织中提取的RNA进行Northern杂交分析，对从分散的和精选的平滑肌细胞中提取的RNA进行RT-PCR分析，结果表明Kv2.2在犬胃肠道所有区域的平滑肌细胞和几个血管组织中都有表达。将Kv2.2 m RNA注入非洲爪哇卵母细胞，可产生一条缓慢激活的K+电流(至半最大电流的时间为97+/-8.6ms)，该电流由15ps(对称性K+)单通道介导。该电流被四乙基铵(IC50=2.6 mM)、4-氨基吡啶(+20 mV时IC50=1.5 mM)和奎宁(IC50=13.7mU/M)所抑制，对轮藻毒素不敏感。低浓度奎宁(1mU M)优先阻断结肠肌细胞延迟整流电流的慢成分。这些数据表明，Kv2.2可能参与了天然胃肠道平滑肌细胞的这种电流。
Kv2.2, homologous to the shab family of Drosophila voltage-gated K+ channels, was isolated from human and canine colonic circular smooth muscle-derived mRNA. Northern hybridization analysis performed on RNA prepared from tissues and RT-PCR performed on RNA isolated from dispersed and selected smooth muscle cells demonstrate that Kv2.2 is expressed in smooth muscle cells found in all regions of the canine gastrointestinal (GI) tract and in several vascular tissues. Injection of Kv2.2 mRNA into Xenopus oocytes resulted in the expression of a slowly activating K+ current (time to half maximum current, 97 +/- 8.6 ms) mediated by 15 pS (symmetrical K+) single channels. The current was inhibited by tetraethylammonium (IC50 = 2.6 mM), 4-aminopyridine (IC50 = 1.5 mM at +20 mV), and quinine (IC50 = 13.7 mu M) and was insensitive to charybdotoxin. Low concentrations of quinine (1 mu M) were used to preferentially block the slow component of the delayed rectifier current in native colonic myocytes. These data suggest that Kv2.2 may contribute to this current in native GI smooth muscle cells.