Closed-state inactivation in Kv4.3 isoforms is differentially modulated by protein kinase C.
Closed-state inactivation in Kv4.3 isoforms is differentially modulated by protein kinase C.
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Kv4.3 亚型的闭合状态失活受蛋白激酶 C 的差异调节。
DOI：
10.1152/ajpcell.00144.2009
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Strauss,HaroldC
中科院分区：
文献类型：
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作者：
Xie,Chang;Bondarenko,VladimirE;Morales,MichaelJ;Strauss,HaroldC
Kv4.3具有复杂的开放和闭合状态失活（CSI）特征，是早期心脏复极的主要贡献者。两种可变剪接形式Kv4.3-短（Kv4.3-S）和Kv4.3-长（Kv4.3-L）的不同之处在于第六跨膜区段下游存在19个氨基酸的插入物。同种型在动力学上相似;然而，较长的形式具有独特的PKC磷酸化位点。要测试的可能性，失活差异调节磷酸化，我们表达的Kv4.3异构体在非洲爪蟾卵母细胞和研究其失活特性的变化后，刺激PKC活性。虽然在开放状态失活没有差异，但在CSI中存在显著差异。在Kv4.3-S中，PMA在−50 mV下14.4 s后使CSI幅度降低24%。相比之下，在相同条件下，Kv4.3-L中CSI的幅度增加了25%。在Kv4.3-L特有的PKC共有识别序列内，将一个puperase磷酸化的苏氨酸（T504）突变为天冬氨酸，消除了PMA反应。CSI的变化是独立的用于增加PKC活性的干预，获得相同的结果与PMA或注射纯化的PKC。我们以前发表的11态模型密切模拟我们的实验数据。我们的数据表明Kv4.3中PKC对CSI的亚型特异性调节，并表明Kv4.3的羧基末端在CSI的调节中发挥重要作用。
Kv4.3, with its complex open- and closed-state inactivation (CSI) characteristics, is a primary contributor to early cardiac repolarization. The two alternatively spliced forms, Kv4.3-short (Kv4.3-S) and Kv4.3-long (Kv4.3-L), differ by the presence of a 19-amino acid insert downstream from the sixth transmembrane segment. The isoforms are similar kinetically; however, the longer form has a unique PKC phosphorylation site. To test the possibility that inactivation is differentially regulated by phosphorylation, we expressed the Kv4.3 isoforms in Xenopus oocytes and examined changes in their inactivation properties after stimulation of PKC activity. Whereas there was no difference in open-state inactivation, there were profound differences in CSI. In Kv4.3-S, PMA reduced the magnitude of CSI by 24% after 14.4 s at −50 mV. In contrast, the magnitude of CSI in Kv4.3-L increased by 25% under the same conditions. Mutation of a putatively phosphorylated threonine (T504) to aspartic acid within a PKC consensus recognition sequence unique to Kv4.3-L eliminated the PMA response. The change in CSI was independent of the intervention used to increase PKC activity; identical results were obtained with either PMA or injected purified PKC. Our previously published 11-state model closely simulated our experimental data. Our data demonstrate isoform-specific regulation of CSI by PKC in Kv4.3 and show that the carboxy terminus of Kv4.3 plays an important role in regulation of CSI.