KCNE4 domains required for inhibition of KCNQ1
KCNE4 domains required for inhibition of KCNQ1
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DOI：
10.1113/jphysiol.2008.161281
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发表时间：
2009-01-15
影响因子：
5.5
通讯作者：
George, Alfred L., Jr.
中科院分区：
文献类型：
--
作者：
Manderfield, Lauren J.;Daniels, Melissa A.;George, Alfred L., Jr.
电压门控钾 (K-v) 通道由单跨膜域辅助亚基 KCNE 家族的成员以不同的方式进行调节。 KCNE4 对 KCNQ1 具有显着的抑制作用，与 KCNE1 和 KCNE3 的激活作用有很大不同。 KCNE4 实现这种行为的结构特征尚不清楚。我们利用 KCNE1、KCNE3 和 KCNE4 的嵌合体来鉴定对异源表达的 KCNQ1 产生抑制作用的特定结构域。先前对 KCNE1 和 KCNE3 的结构功能分析确定了跨膜结构域内的一个关键三肽基序，该基序解释了这两种 KCNE 蛋白引起的 KCNQ1 调节的差异。将 KCNE4 的跨膜三肽基序与 KCNE1 的相应氨基酸序列交换不会影响任一蛋白质的行为。类似地，交换KCNE3和KCNE4的三肽区域进一步证明这种跨膜基序不能解释KCNE4的活性。使用更系统的方法，我们证明了 KCNE4 C 末端对于 KCNQ1 调制至关重要。用 KCNE4 的 C 端替换 KCNE1 或 KCNE3 的 C 端产生了强烈抑制 KCNQ1 的嵌合蛋白。其他证据支持 KCNE4 跨膜结构域的合作作用。尽管 C 末端对于 KCNE4 活性是必需的，但我们证明源自细胞因子受体 CD8 的替代跨膜结构域不能抑制 KCNQ1，表明单独的 KCNE4 C 末端不足以调节 KCNQ1。我们进一步证明 KCNE4 C 末端与 KCNQ1 相互作用。我们的数据揭示了 KCNE4 的重要结构-功能关系，有助于加深我们对 KCNE 蛋白调节钾通道的理解。
Voltage-gated potassium (K-v) channels are modulated in distinct ways by members of the KCNE family of single transmembrane domain accessory subunits. KCNE4 has a dramatic inhibitory effect on KCNQ1 that differs substantially from the activating effects of KCNE1 and KCNE3. The structural features of KCNE4 that enable this behaviour are unknown. We exploited chimeras of KCNE1, KCNE3 and KCNE4 to identify specific domains responsible for the inhibitory effects on heterologously expressed KCNQ1. Previous structure-function analysis of KCNE1 and KCNE3 identified a critical tripeptide motif within the transmembrane domain that accounts for the differences in KCNQ1 modulation evoked by these two KCNE proteins. Swapping the transmembrane tripeptide motif of KCNE4 with the corresponding amino acid sequence of KCNE1 did not influence the behaviour of either protein. Similarly, exchanging the tripeptide regions of KCNE3 and KCNE4 further demonstrated that this transmembrane motif does not explain the activity of KCNE4. Using a more systematic approach, we demonstrated that the KCNE4 C-terminus was critical for KCNQ1 modulation. Replacement of the KCNE1 or KCNE3 C-termini with that of KCNE4 created chimeric proteins that strongly inhibited KCNQ1. Additional evidence supported a cooperative role of the KCNE4 transmembrane domain. Although the C-terminus was necessary for KCNE4 activity, we demonstrated that a surrogate transmembrane domain derived from the cytokine receptor CD8 did not enable inhibition of KCNQ1, indicating that the KCNE4 C-terminus alone was not sufficient for KCNQ1 modulation. We further demonstrated that the KCNE4 C-terminus interacts with KCNQ1. Our data reveal important structure-function relationships for KCNE4 that help advance our understanding of potassium channel modulation by KCNE proteins.