Inhibition of lysosomal degradation rescues pentamidine-mediated decreases of K(IR)2.1 ion channel expression but not that of K(v)11.1.
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 (I(Kr)) and inward (I(K1)) rectifier currents in cultured adult canine cardiomyocytes. In HEK293 cells, pentamidine inhibits functional K(v)11.1 channels, responsible for I(Kr), by interfering at the level of full glycosylation, yielding less mature form of K(v)11.1 at the plasma membrane. In contrast, total K(IR)2.1 expression levels, underlying I(K1), are strongly decreased, which cannot be explained from mRNA expression levels. No changes in molecular size of K(IR)2.1 protein were observed, excluding interference in overt glycosylation. Remaining K(IR)2.1 protein is mainly expressed at the plasma membrane. Inhibition of lysosomal protein degradation is able to partially rescue K(IR)2.1 levels, but not those of K(v)11.1. 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.
Department of Medical Physiology, Division of Heart & Lung, University Medical Center Utrecht, The Netherlands.
Lukas
L
Nalos
Teun P
TP
de Boer
Marien J C
MJ
Houtman
Martin B
MB
Rook
Marc A
MA
Vos
Marcel A G
MA
van der Heyden
D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D015153:Blotting, Western; D002478:Cells, Cultured; D004285:Dogs; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D008247:Lysosomes / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D018613:Microscopy, Confocal; D018408:Patch-Clamp Techniques; D010419:Pentamidine / Q000494:pharmacology*; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000981:Antiprotozoal Agents; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C489461:Kir2.1 channel; D024661:Potassium Channels, Inwardly Rectifying; D012333:RNA, Messenger; D010419:Pentamidine