MinK subdomains that mediate modulation of and association with KvLQT1

被引:76
作者
Tapper, AR
George, AL [1 ]
机构
[1] Vanderbilt Univ, Med Ctr, Div Med Genet 451 MRB2, Sch Med,Dept Pharmacol, Nashville, TN 37232 USA
[2] Vanderbilt Univ, Sch Med, Dept Med, Nashville, TN 37232 USA
关键词
KCNQ1; heart; long QT syndrome; potassium channel; KCNE1;
D O I
10.1085/jgp.116.3.379
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
KvLQT1 is a voltage-gated potassium channel expressed in cardiac cells that is critical for myocardial repolarization. When expressed alone in heterologous expression systems, KvLQT1 channels exhibit a rapidly activating potassium current that slowly deactivates. MinK, a 129 amino acid protein containing one transmembrane-spanning domain modulates KvLQT1, greatly slowing activation, increasing current amplitude, and removing inactivation. Using deletion and chimeric analysis, we have examined the structural determinants of MinK effects on gating modulation and subunit association. Coexpression of KvLQT1 with a MinK COOH-terminus deletion mutant (MinK Delta Cterm) in Xenopus oocytes resulted in a rapidly activated potassium current closely resembling currents recorded from oocytes expressing KvLQT1 alone, indicating that this region is necessary for modulation. To determine whether MinK Delta Cterm was associated with KvLQT1, a functional tag (G55C) that confers susceptibility to partial block by external cadmium was engineered into the transmembrane domain of MinK Delta Cterm. Currents derived from coexpression of KvLQT1 with MinK Delta Cterm were cadmium sensitive, suggesting that MinK Delta Cterm does associate with KvLQT1, but does not modulate gating. To determine which MinK regions are sufficient for KvLQT1 association and modulation, chimeras were generated between MinK and the Na+ channel Pi subunit. Chimeras between MinK and Pi could only modulate KvLQT1 if they contained both the MinK transmembrane domain and COOH terminus, suggesting that the MinK COOH terminus alone is not sufficient for KvLQT1 modulation, and requires an additional, possibly associative interaction between the MinK transmembrane domain and KvLQT1. To identify the MinK subdomains necessary for gating modulation, deletion mutants were designed and coexpressed with KvLQT1. A MinK construct with amino acid residues 94-129 deleted retained the ability to modulate KvLQT1 gating, identifying the COOH-terminal region critical for gating modulation. Finally, MinK/MiRP1 (MinK related protein-1) chimeras were generated to investigate the difference between these two closely related subunits in their ability to modulate KvLQT1. The results from this analysis indicate that MiRP1 cannot modulate KvLQT1 due to differences within the transmembrane domain. Our results allow us to identify the MinK subdomains that mediate KvLQT1 association and modulation.
引用
收藏
页码:379 / 389
页数:11
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