Eldstrom Jodene, Choi Woo Sung, Steele David F, Fedida David
Department of Physiology, University of British Columbia, 2146 Health Sciences Mall, V6T 1Z3, Vancouver, BC, Canada.
FEBS Lett. 2003 Jul 17;547(1-3):205-11. doi: 10.1016/s0014-5793(03)00668-9.
The functional interaction of the voltage-gated potassium channel hKv1.5 with the PDZ domain containing protein SAP97 has been investigated. In marked contrast with the known dependence of SAP97-induced Kv1 potassium current down-regulation on the channel C-termini, SAP97 increased hKv1.5 current through an indirect interaction with the Kv1.5 N-terminus. Deletion of the Kv1.5 N-terminus eliminated the SAP97-mediated increase in potassium currents whereas deletion of the channel's C-terminal PDZ binding motif had no effect. In contrast with other Kv1-SAP97 interactions, no physical interaction could be detected in vivo or in vitro between the two proteins. The proteins did not co-localize in cardiac myocytes nor did they co-immunoprecipitate from transfected HEK cells. Yeast two-hybrid experiments also failed to detect any interaction between the two proteins, but in one experiment of six, Kv1.5 co-immunoprecipitated very inefficiently with SAP97 from rat ventricular myocytes. Thus, we conclude that the influence of SAP97 on Kv1.5 potassium current levels is dependent upon a novel regulatory mechanism.
对电压门控钾通道hKv1.5与含PDZ结构域蛋白SAP97之间的功能相互作用进行了研究。与已知的SAP97诱导的Kv1钾电流下调对通道C末端的依赖性形成鲜明对比的是，SAP97通过与Kv1.5 N末端的间接相互作用增加了hKv1.5电流。缺失Kv1.5 N末端消除了SAP97介导的钾电流增加，而缺失通道的C末端PDZ结合基序则没有影响。与其他Kv1-SAP97相互作用不同，在体内或体外均未检测到这两种蛋白之间的物理相互作用。这两种蛋白在心肌细胞中不共定位，也不能从转染的HEK细胞中共免疫沉淀。酵母双杂交实验也未能检测到这两种蛋白之间的任何相互作用，但在六个实验中的一个实验中，Kv1.5与大鼠心室肌细胞中的SAP97共免疫沉淀效率极低。因此，我们得出结论，SAP97对Kv1.5钾电流水平的影响取决于一种新的调节机制。
