Jansen John A, de Boer Teun P, Wolswinkel Rianne, van Veen Toon A B, Vos Marc A, van Rijen Harold V M, van der Heyden Marcel A G
Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands.
Biochem Biophys Res Commun. 2008 Mar 14;367(3):687-92. doi: 10.1016/j.bbrc.2007.12.168. Epub 2008 Jan 7.
The inward rectifier current generated by Kir2.1 ion channel proteins is primarily responsible for the stable resting membrane potential in various excitable cell types, like neurons and myocytes. Tight regulation of Kir2.1 functioning prevents premature action potential formation and ensures optimal repolarization times. While Kir2.1 forward trafficking has been addressed in a number of studies, its degradation pathways are thus far unknown. Using three different lysosomal inhibitors, NH(4)Cl, chloroquine and leupeptin, we now demonstrate involvement of the lysosomal degradation pathway in Kir2.1 breakdown. Upon application of the inhibitors, increased steady state protein levels are detectable within few hours coinciding with intracellular granular Kir2.1 accumulation. Treatment for 24h with either chloroquine or leupeptin results in increased plasmamembrane originating inward rectifier current densities, while current-voltage characteristics remain unaltered. We conclude that the lysosomal degradation pathway contributes to Kir2.1 mediated inward rectifier current regulation.
由Kir2.1离子通道蛋白产生的内向整流电流主要负责多种可兴奋细胞类型（如神经元和心肌细胞）中稳定的静息膜电位。对Kir2.1功能的严格调节可防止过早形成动作电位，并确保最佳的复极化时间。虽然已有多项研究探讨了Kir2.1的正向运输，但迄今为止其降解途径尚不清楚。我们使用三种不同的溶酶体抑制剂NH(4)Cl、氯喹和亮抑酶肽，现在证明溶酶体降解途径参与了Kir2.1的降解。应用抑制剂后，在数小时内可检测到稳态蛋白水平升高，同时伴有细胞内颗粒状Kir2.1积累。用氯喹或亮抑酶肽处理24小时会导致源自质膜的内向整流电流密度增加，而电流-电压特性保持不变。我们得出结论，溶酶体降解途径有助于Kir2.1介导的内向整流电流调节。
