title: Pharmacological rescue of trafficking defective HERG channels formed by coassembly of wild-type and long QT mutant N470D subunits.
abstract: Mutations in the human ether-a-go-go-related gene (HERG) cause long QT syndrome. We previously showed that the HERG N470D mutation expressed as homotetrameric channels causes a protein trafficking defect, and this can be corrected by the HERG channel blocking drug E-4031. The N470D mutant also has been reported to cause dominant negative suppression of HERG current when coexpressed with wild-type channel subunits. The aims of this study were 1). to investigate the molecular mechanism responsible for the dominant negative effect of the N470D mutant coexpressed with wild-type subunits and 2). to test whether the trafficking defective heteromeric channels could be pharmacologically rescued by E-4031. Using a combination of immunoprecipitation and Western blot methods, we showed that N470D mutant and wild-type HERG subunits were physically associated in the endoplasmic reticulum as heteromeric channels. The coassembly resulted in the retention of both wild-type and N470D subunits in the endoplasmic reticulum. Culturing cells in E-4031 increased the cell surface expression of these channels, although with an altered electrophysiological phenotype. These results suggest that the dominant negative effect of the N470D wild-type coassembled channels is caused by retention of heteromeric channels in the endoplasmic reticulum and that the trafficking defect of these channels can be corrected by specific pharmacological strategies.
authors.affiliation: Deparrtment of Medicine, Oregon Health and Science University, Portland, OR 97239, USA.
authors.forename: Qiuming
authors.initials: Q
authors.lastname: Gong
authors.forename: Corey L
authors.initials: CL
authors.lastname: Anderson
authors.forename: Craig T
authors.initials: CT
authors.lastname: January
authors.forename: Zhengfeng
authors.initials: Z
authors.lastname: Zhou
mesh_terms: D027682:Cation Transport Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D051638:Ether-A-Go-Go Potassium Channels; D005799:Genes, Dominant; D006801:Humans; D008133:Long QT Syndrome / Q000235:genetics*; D009154:Mutation; D018408:Patch-Clamp Techniques; D010641:Phenotype; D010880:Piperidines / Q000494:pharmacology; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D011725:Pyridines / Q000494:pharmacology
chemical_list: D027682:Cation Transport Proteins; D051638:Ether-A-Go-Go Potassium Channels; C092509:KCNH6 protein, human; D010880:Piperidines; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011725:Pyridines; C063968:E 4031