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1 The Rammelkamp Center for Education and Research, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio 44109-1998; 2 Molecular Cardiology, Fondazione Salvatore Maugeri, Pavia; and 3 Department of Cardiology, University of Pavia and Policlinico S. Matteo Instituto di Ricovero e Cura a Carattene Scientifico, 27100 Pavia, Italy
Mutations in the cardiac potassium ion channel gene
KCNQ1 (voltage-gated K+ channel subtype KvLQT1)
cause LQT1, the most common type of hereditary long Q-T syndrome.
KvLQT1 mutations prolong Q-T by reducing the repolarizing cardiac
current [slow delayed rectifier K+ current
(IKs )], but, for reasons that are not well
understood, the clinical phenotypes may vary considerably even for
carriers of the same mutation, perhaps explaining the mode of
inheritance. At present, only currents expressed by LQT1 mutants have
been studied, and it is unknown whether abnormal subunits are
transported to the cell surface. Here, we have examined for the first
time trafficking of KvLQT1 mutations and correlated the results with the IKs currents that were expressed. Two
missense mutations, S225L and A300T, produced abnormal currents, and
two others, Y281C and Y315C, produced no currents. However, all four
KvLQT1 mutations were detected at the cell surface. S225L, Y281C, and
Y315C produced dominant negative effects on wild-type
IKs current, whereas the mutant with the mildest
dysfunction, A300T, did not. We examined trafficking of a severe
insertion deletion mutant
544 and detected this protein at the cell
surface as well. We compared the cellular and clinical phenotypes and
found a poor correlation for the severely dysfunctional mutations.
KvLQT1 mutations; cellular processing; cellular phenotype; clinical phenotype; slow delayed rectifier potassium current; long Q-T syndrome
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