title: Shared requirement for dynein function and intact microtubule cytoskeleton for normal surface expression of cardiac potassium channels.
abstract: Potassium channels at the cardiomyocyte surface must eventually be internalized and degraded, and changes in cardiac potassium channel expression are known to occur during myocardial disease. It is not known which trafficking pathways are involved in the control of cardiac potassium channel surface expression, and it is not clear whether all cardiac potassium channels follow a common pathway or many pathways. In the present study we have surveyed the role of retrograde microtubule-dependent transport in modulating the surface expression of several cardiac potassium channels in ventricular myocytes and heterologous cells. The disruption of microtubule transport in rat ventricular myocytes with nocodazole resulted in significant changes in potassium currents. A-type currents were enhanced 1.6-fold at +90 mV, rising from control densities of 20.9 +/- 2.8 to 34.0 +/- 5.4 pA/pF in the nocodazole-treated cells, whereas inward rectifier currents were reduced by one-third, perhaps due to a higher nocodazole sensitivity of Kir channel forward trafficking. These changes in potassium currents were associated with a significant decrease in action potential duration. When expressed in heterologous human embryonic kidney (HEK-293) cells, surface expression of Kv4.2, known to substantially underlie A-type currents in rat myocytes, was increased by nocodazole, by the dynein inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride, and by p50 overexpression, which specifically interferes with dynein motor function. Peak current density was 360 +/- 61.0 pA/pF in control cells and 658 +/- 94.5 pA/pF in cells overexpressing p50. The expression levels of Kv2.1, Kv3.1, human ether-a-go-go-related gene, and Kir2.1 were similarly increased by p50 overexpression in this system. Thus the regulation of potassium channel expression involves a common dynein-dependent process operating similarly on the various channels.
authors.affiliation: Dept. of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada V6T 1Z3.
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Loewen
authors.forename: Zhuren
authors.initials: Z
authors.lastname: Wang
authors.forename: Jodene
authors.initials: J
authors.lastname: Eldstrom
authors.forename: Alireza
authors.initials: A
authors.lastname: Dehghani Zadeh
authors.forename: Anu
authors.initials: A
authors.lastname: Khurana
authors.forename: David F
authors.initials: DF
authors.lastname: Steele
authors.forename: David
authors.initials: D
authors.lastname: Fedida
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D019921:Biotinylation; D000090007:CLC-2 Chloride Channels; D002460:Cell Line; D018118:Chloride Channels / Q000096:biosynthesis / Q000235:genetics; D003599:Cytoskeleton / Q000502:physiology*; D004398:Dyneins / Q000502:physiology*; D004594:Electrophysiology; D019286:Endopeptidase K / Q000378:metabolism; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles; D006801:Humans; D008870:Microtubules / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism / Q000648:ultrastructure; D032383:Myocytes, Cardiac / Q000502:physiology; D052002:NF-kappa B p50 Subunit / Q000096:biosynthesis; D015739:Nocodazole / Q000494:pharmacology; D010957:Plasmids / Q000235:genetics; D015221:Potassium Channels / Q000096:biosynthesis*; D011956:Receptors, Cell Surface / Q000378:metabolism; D014162:Transfection
chemical_list: D000970:Antineoplastic Agents; D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; D052002:NF-kappa B p50 Subunit; D015221:Potassium Channels; D011956:Receptors, Cell Surface; C010192:9-(2-hydroxy-3-nonyl)adenine; D019286:Endopeptidase K; D004398:Dyneins; D000225:Adenine; D015739:Nocodazole