KvLQT1 and hERG are the α-subunits of the voltage-gated K⁺ channels which carry the cardiac repolarizing currents IKs and IKr, respectively. These currents function in vivo with some redundancy to maintain appropriate action potential durations (APDs) in cardiomyocytes. As such, protein-protein interactions between hERG and KvLQT1 may be important in normal cardiac electrophysiology, as well as in arrhythmia and sudden cardiac death. Previous phenomenological observations of functional, mutual downregulation between these complementary repolarizing currents in transgenic rabbit models and human cell culture motivate our investigations into protein-protein interactions between hERG and KvLQT1. Previous data suggest that a dynamic, physical interaction between hERG and KvLQT1 modulates the respective currents. However, the mechanism by which hERG-KvLQT1 interactions are regulated is still poorly understood. Phosphorylation is proposed to play a role since modifying the phosphorylation state of each protein has been shown to alter channel kinetics, and both hERG and KvLQT1 are targets of the Ser/Thr protein kinase PKA, activated by elevated intracellular cAMP. In this work, quantitative apFRET analyses of phosphonull and phosphomimetic hERG and KvLQT1 mutants indicate that unphosphorylated hERG does not interact with KvLQT1, suggesting that hERG phosphorylation is important for wild-type proteins to interact. For proteins already potentially interacting, phosphorylation of KvLQT1 appears to be the driving factor abrogating hERG-KvLQT1 interaction. This work increases our knowledge about hERG-KvLQT1 interactions, which may contribute to the efforts to elucidate mechanisms that underlie many types of arrhythmias, and also further characterizes novel protein-protein interactions between two distinct potassium channel families.

KvLQT1和hERG是电压门控的K ⁺的α亚基分别携带心脏复极电流IKs和IKr的通道。这些电流在体内具有一定的冗余性，以维持心肌细胞中适当的动作电位持续时间（APD）。因此，hERG和KvLQT1之间的蛋白质相互作用对正常的心脏电生理以及心律不齐和心脏猝死都可能很重要。在转基因兔模型和人类细胞培养物中这些互补的复极电流之间的功能性，相互下调的先前现象学观察，促使我们对hERG和KvLQT1之间的蛋白质相互作用进行了研究。先前的数据表明，hERG和KvLQT1之间的动态，物理相互作用调节了各自的电流。但是，尚不清楚如何调控hERG-KvLQT1相互作用的机制。磷酸化被认为发挥了作用，因为已表明改变每种蛋白质的磷酸化状态会改变通道动力学，并且hERG和KvLQT1都是Ser / Thr蛋白激酶PKA的靶标，并通过升高的细胞内cAMP激活。在这项工作中，对磷酸化和模拟磷酸化的hERG和KvLQT1突变体的定量apFRET分析表明，未磷酸化的hERG不与KvLQT1相互作用，这表明hERG磷酸化对于野生型蛋白的相互作用很重要。对于已经潜在相互作用的蛋白质，KvLQT1的磷酸化似乎是废除hERG-KvLQT1相互作用的驱动因素。这项工作增加了我们对hERG-KvLQT1相互作用的了解，这可能有助于阐明许多类型的心律不齐的机制，