title: Intragenic suppression of trafficking-defective KCNH2 channels associated with long QT syndrome.
abstract: Mutations in the KCNH2 or human ether-a-go-go-related gene-encoded K(+) channel reduce functional KCNH2 current (I(KCNH2)) to cause long QT syndrome (LQT2) by multiple mechanisms, including defects in intracellular transport (trafficking). Trafficking-deficient, or class 2, LQT2 mutations reduce the Golgi processing and surface membrane expression of KCNH2 channel proteins. Drugs that associate with pore-S6 intracellular drug binding domain of KCNH2 channel proteins to cause high-affinity block of I(KCNH2) also can increase the processing of class 2 LQT2 channel proteins through the secretory pathway. We used a strategy of intragenic suppression to test the hypothesis that amino acid substitutions in the putative drug binding domain at residue Y652 could compensate for protein folding abnormalities caused by class 2 LQT2 mutations. We found that the Y652C substitution, and to lesser extent the Y652S substitution, resulted in intragenic suppression of the class 2 LQT2 G601S phenotype; these substitutions increased Golgi processing of G601S channel proteins. The Y652C substitution also caused intragenic suppression of the class 2 LQT2 V612L and F640V phenotypes but not the LQT2 N470D or F805C phenotypes. These are the first findings to demonstrate that a single amino acid substitution in the putative KCNH2 drug binding domain can cause intragenic suppression of several LQT2 mutations.
authors.affiliation: Department of Medicine, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Delisle
authors.forename: Jessica K
authors.initials: JK
authors.lastname: Slind
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Kilby
authors.forename: Corey L
authors.initials: CL
authors.lastname: Anderson
authors.forename: Blake D
authors.initials: BD
authors.lastname: Anson
authors.forename: Ravi C
authors.initials: RC
authors.lastname: Balijepalli
authors.forename: David J
authors.initials: DJ
authors.lastname: Tester
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ackerman
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Kamp
authors.forename: Craig T
authors.initials: CT
authors.lastname: January
mesh_terms: D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D006801:Humans; D015640:Ion Channel Gating / Q000235:genetics; D008133:Long QT Syndrome / Q000235:genetics* / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics* / Q000378:metabolism*; D021381:Protein Transport / Q000235:genetics; D013489:Suppression, Genetic
chemical_list: D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D024642:Potassium Channels, Voltage-Gated