Contribution of Kv4 channels toward the A-type potassium current in murine colonic myocytes
Contribution of Kv4 channels toward the A-type potassium current in murine colonic myocytes
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DOI：
10.1113/jphysiol.2002.025163
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发表时间：
2002-10-15
影响因子：
5.5
通讯作者：
Sanders, KM
中科院分区：
文献类型：
--
作者：
Amberg, GC;Koh, SD;Sanders, KM
小鼠结肠肌细胞中存在一种快速失活的K+电流（A型电流; I-A），它在维持慢波电活动的生理模式中起重要作用。结肠I-A的动力学曲线类似于Kv4衍生电流。我们使用药理学、分子生物学和免疫组织化学方法研究了Kv4 α亚基对小鼠结肠中I-A的贡献。二价阳离子Cd~（2+）降低了I-A峰，使激活和失活的电压依赖性向更高的去极化电位移动。用La3+观察到类似的结果。结肠I-A对低微摩尔浓度的氟卡尼敏感（IC 50 = 11 μ M）。定量PCR表明，在结肠和空肠组织中，Kv4.3的转录表现出更大的相对丰度比转录编码Kv4.1或Kv4.2。抗体显示更大的Kv4.3样免疫反应比Kv4.2样免疫反应在结肠肌细胞。Kv4样免疫反应在空肠肌细胞中不太明显。为了解决这一发现，我们研究了K+通道相互作用蛋白（KChlPs）的表达，其作为Kv4介导的电流的正调节剂。定性PCR确定转录编码四个已知的KChIP家族成员在分离的结肠和空肠肌细胞。然而，KChIP转录的相对丰度是2.6倍，在结肠组织比空肠，通过定量PCR评估，KChIP1显示优势。这一观察结果与这两种组织中存在的A型电流的幅度一致，其中结肠肌细胞的密度是空肠肌细胞的两倍。由此我们得出结论，Kv4.3，与KChIP 1，是主要的分子决定因素的I-A在小鼠结肠肌细胞。
A rapidly inactivating K+ current (A-type current; I-A) present in murine colonic myocytes is important in maintaining physiological patterns of slow wave electrical activity. The kinetic profile of colonic I-A resembles that of Kv4-derived currents. We examined the contribution of Kv4 alpha-subunits to I-A in the murine colon using pharmacological, molecular and immunohistochemical approaches. The divalent cation Cd2+ decreased peak I-A and shifted the voltage dependence of activation and inactivation to more depolarized potentials. Similar results were observed with La3+. Colonic I-A was sensitive to low micromolar concentrations of flecainide (IC50 = 11 muM). Quantitative PCR indicated that in colonic and jejunal tissue, Kv4.3 transcripts demonstrate greater relative abundance than transcripts encoding Kv4.1 or Kv4.2. Antibodies revealed greater Kv4.3-like immunoreactivity than Kv4.2-like immunoreactivity in colonic myocytes. Kv4-like immunoreactivity was less evident in jejunal myocytes. To address this finding, we examined the expression of K+ channel-interacting proteins (KChlPs), which act as positive modulators of Kv4-mediated currents. Qualitative PCR identified transcripts encoding the four known members of the KChIP family in isolated colonic and jejunal myocytes. However, the relative abundance of KChIP transcript was 2.6-fold greater in colon tissue than in jejunum, as assessed by quantitative PCR, with KChIP1 showing predominance. This observation is in accordance with the amplitude of the A-type current present in these two tissues, where colonic myocytes possess densities twice that of jejunal myocytes. From this we conclude that Kv4.3, in association with KChIP1, is the major molecular determinant of I-A in murine colonic myocytes.