Functional properties of a brain-specific NH2-terminally spliced modulator of Kv4 channels
Functional properties of a brain-specific NH2-terminally spliced modulator of Kv4 channels
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DOI：
10.1152/ajpcell.00416.2002
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发表时间：
2003-07-01
影响因子：
5.5
通讯作者：
O'Grady, SM
中科院分区：
文献类型：
--
作者：
Boland, LM;Jiang, M;O'Grady, SM
Kv4/K通道相互作用蛋白（KChIP）钾通道是大脑和心脏中一类快速失活的钾通道。考虑到选择性剪接对KChIP门控调制定量特征的重要性，我们对KChIP1先前未被表征的剪接形式进行了功能表征。KChIP1b剪接变体与先前表征的KChIP1a剪接形式的不同之处在于包含了一个新的氨基末端区域，该区域由小鼠、大鼠和人类基因中保守的另一个外显子编码。KChIP1b mRNA在脑组织中高表达，但在心脏和肝脏中未检测到。在小脑组织中，KChIP1b和KChIP1a转录本的表达水平几乎相等。卵母细胞中KChIP1b或KChIP1a与Kv4.2通道的共表达减缓了K电流衰减并破坏了开放失活通道门控的稳定性。与其他KChIP亚基一样，KChIP1b增加了Kv4.2电流幅值，KChIP1b也使Kv4.2的电导-电压曲线偏移了-10 mV。KChIP1b共表达使封闭门控状态下的Kv4.2通道失活发展更快。KChIP1b中新的氨基末端区域的缺失选择性地改变了亚基对Kv4.2闭合失活门控的调节。通过直接比较nh2末端缺失突变体和KChIP1a亚基的特性，进一步证实了KChIP1b nh2末端区域的作用，KChIP1a亚基由缺乏新外显子的转录本编码。KChIP1b调节Kv4通道的特征可能在哺乳动物中保守，并证明KChIP1 nh2末端区域在调节闭合失活门控中的作用。
Kv4/K channel-interacting protein (KChIP) potassium channels are a major class of rapidly inactivating K channels in brain and heart. Considering the importance of alternative splicing to the quantitative features of KChIP gating modulation, a previously uncharacterized splice form of KChIP1 was functionally characterized. The KChIP1b splice variant differs from the previously characterized KChIP1a splice form by the inclusion of a novel amino-terminal region that is encoded by an alternative exon that is conserved in mouse, rat, and human genes. The expression of KChIP1b mRNA was high in brain but undetectable in heart or liver by RT-PCR. In cerebellar tissue, KChIP1b and KChIP1a transcripts were expressed at nearly equal levels. Coexpression of KChIP1b or KChIP1a with Kv4.2 channels in oocytes slowed K current decay and destabilized open-inactivated channel gating. Like other KChIP subunits, KChIP1b increased Kv4.2 current amplitude and KChIP1b also shifted Kv4.2 conductance-voltage curves by -10 mV. The development of Kv4.2 channel inactivation accessed from closed gating states was faster with KChIP1b coexpression. Deletion of the novel amino-terminal region in KChIP1b selectively altered the subunit's modulation of Kv4.2 closed inactivation gating. The role of the KChIP1b NH2-terminal region was further confirmed by direct comparison of the properties of the NH2-terminal deletion mutant and the KChIP1a subunit, which is encoded by a transcript that lacks the novel exon. The features of KChIP1b modulation of Kv4 channels are likely to be conserved in mammals and demonstrate a role for the KChIP1 NH2-terminal region in the regulation of closed inactivation gating.