N. Schmitt et al., A recessive C-terminal Jervell and Lange-Nielsen mutation of the KCNQ1 channel impairs subunit assembly, EMBO J, 19(3), 2000, pp. 332-340
The LQT1 locus (KCNQ1) has been correlated with the most common form of inh
erited long QT (LQT) syndrome. LQT patients suffer from syncopal episodes a
nd high risk of sudden death. The KCNQ1 gene encodes KvLQT1 alpha-subunits,
which together with auxiliary IsK (KCNE1, minK) subunits form IKs K+ chann
els, Mutant KvLQT1 subunits may be associated either with an autosomal domi
nant form of inherited LQT, Romano-Ward syndrome, or an autosomal recessive
form, Jervell and Lange-Nielsen syndrome (JLNS). We have identified a smal
l domain between residues 589 and 620 in the KvLQT1 C-terminus, which may f
unction as an assembly domain for KvLQT1 subunits, KvLQT1 C-termini do not
assemble and KvLQT1 subunits do not express functional K+ channels without
this domain. We showed that a JLN deletion-insertion mutation at KvLQT1 res
idue 544 eliminates important parts of the C-terminal assembly domain. Ther
efore, JLN mutants may be defective in KvLQT1 subunit assembly, The results
pro,ide a molecular basis for the clinical observation that heterozygous J
LN carriers show slight cardiac dysfunctions and that the severe JLNS pheno
type is characterized by the absence of KvLQT1 channel.