Intragenic suppression of trafficking-defective KCNH2 channels associated with long QT syndrome.
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.
Delisle
Brian P
BP
Department of Medicine, University of Wisconsin, Madison, Wisconsin 53706, USA.
Slind
Jessica K
JK
Kilby
Jennifer A
JA
Anderson
Corey L
CL
Anson
Blake D
BD
Balijepalli
Ravi C
RC
Tester
David J
DJ
Ackerman
Michael J
MJ
Kamp
Timothy J
TJ
January
Craig T
CT
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
D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D024642:Potassium Channels, Voltage-Gated