Large-scale mutational analysis of Kv11.1 reveals molecular insights into type 2 long QT syndrome

Abstract

It has been suggested that deficient protein trafficking to the cell membrane is the dominant mechanism associated with type 2 Long QT syndrome (LQT2) caused by Kv11.1 potassium channel missense mutations, and that for many mutations the trafficking defect can be corrected pharmacologically. However, this inference was based on expression of a small number of Kv11.1 mutations. We performed a comprehensive analysis of 167 LQT2-linked missense mutations in four Kv11.1 structural domains and found that deficient protein trafficking is the dominant mechanism for all domains except for the distal C-terminus. Also, most pore mutations—in contrast to intracellular domain mutations —were found to have severe dominant-negative effects when co-expressed with wild type subunits. Finally, pharmacological correction of the trafficking defect in homomeric mutant channels was possible for mutations within all structural domains. However, pharmacological correction is dramatically improved for pore mutants when co-expressed with wild type subunits to form heteromeric channels.

Dominant negative consequences of a hERG 1b-specific mutation associated with intrauterine fetal death

“…To assess defects in channel trafficking commonly associated with hERG mutations (Anderson et al, 2006; Anderson et al, 2014), we measured maturation of protein from the ER-associated glycoform to the mature, Golgi-glycosylated form destined for the plasma membrane (Zhou et al, 1999). Using western blot analysis, we measured the mature glycoform normalized to total protein for hERG 1b and 1b-R25W.…”

“…Numerous 1a-specific mutations have been identified and shown to cause trafficking and functional defects (Anderson et al, 2006; Anderson et al, 2014). Genetic evidence for 1b-specific disease mutations is limited to two clinical cases (Crotti et al, 2013; Sale et al, 2008).…”

Mouse ERG K + Channel Clones Reveal Differences in Protein Trafficking and Function

“…4,14 Consequently, in this study, we hypothesized that mERG‐London channels would be trafficking deficient, whereas mERG‐Nie and mERG‐Waterston channels would traffic to the cell membrane, and that the voltage dependence of channel gating was likely to be different for the 3 mERG channels, given the differing locations of amino acid substitutions. Some LQT2 missense mutations in non‐HOS regions are known to result in channels that traffic normally but gate abnormally.…”

“…The hERG channel protein contains regions of highly ordered structures (HOS; α‐helices and β‐sheets) in transmembrane and pore domains and in the PAS domain and cyclic nucleotide binding domains in the N‐ and C‐termini, respectively. 4 In addition, it has regions thought not to contain HOS in portions of the N‐ and C‐termini and in some intra‐ and extracellular linker regions. Many LQT2 missense mutations in regions of HOS result in channels that fail to undergo normal protein trafficking to the surface membrane; rather, the mutated proteins are retained in intracellular compartments, including the endoplasmic reticulum, as misfolded proteins and are degraded.…”

Fatty acid analogue N-arachidonoyl taurine restores function of IKs channels with diverse long QT mutations

“…About 80-90% of LQTS type 2-associated hERG mutants are estimated to suffer from defective trafficking (Anderson et al, 2014; Sanguinetti, 2010). The corresponding number for LQTS-associated K V 7.1 and KCNE1 mutants is not known.…”