Inhibition of lysosomal degradation rescues pentamidine-mediated decreases of KIR2.1 ion channel expression but not that of Kᵥ11.1

• Published in: European journal of pharmacology 2011-02, Vol.652 (1-3), p.96-103
• Main Authors: Nalos, Lukas, de Boer, Teun P, Houtman, Marien J.C, Rook, Martin B, Vos, Marc A, van der Heyden, Marcel A.G
• Format: Article
• Language: English
• Subjects: adults; adverse effects; Antibiotics. Antiinfectious agents. Antiparasitic agents; Antiparasitic agents; Biological and medical sciences; cardiomyocytes; confocal laser scanning microscopy; dogs; drugs; gene expression; glycosylation; Medical sciences; messenger RNA; molecular weight; Pharmacology. Drug treatments; plasma membrane; potassium; potassium channels; protein degradation; quantitative polymerase chain reaction; Western blotting
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/j.ejphar.2010.10.093

The antiprotozoal drug pentamidine inhibits two types of cardiac rectifier potassium currents, which can precipitate life-threatening arrhythmias. Here, we use pentamidine as a tool to investigate whether a single drug affects trafficking of two structurally different potassium channels by identical or different mechanisms, and whether the adverse drug effect can be suppressed in a channel specific fashion. Whole cell patch clamp, Western blot, real time PCR, and confocal laser scanning microscopy were used to determine potassium current density, ion channel protein levels, mRNA expression levels, and subcellular localization, respectively. We demonstrate that pentamidine inhibits delayed (IKᵣ) and inward (IK₁) rectifier currents in cultured adult canine cardiomyocytes. In HEK293 cells, pentamidine inhibits functional Kᵥ11.1 channels, responsible for IKᵣ, by interfering at the level of full glycosylation, yielding less mature form of Kᵥ11.1 at the plasma membrane. In contrast, total KIR2.1 expression levels, underlying IK₁, are strongly decreased, which cannot be explained from mRNA expression levels. No changes in molecular size of KIR2.1 protein were observed, excluding interference in overt glycosylation. Remaining KIR2.1 protein is mainly expressed at the plasma membrane. Inhibition of lysosomal protein degradation is able to partially rescue KIR2.1 levels, but not those of Kᵥ11.1. We conclude that 1) a single drug can interfere in cardiac potassium channel trafficking in a subtype specific mode and 2) adverse drug effects can be corrected in a channel specific manner.