hERG ion channels are the target for acquired and inherited long QT syndrome (LQTS), diseases leading to polymorphic ventricular fibrillation and sudden death. Previous work in this lab demonstrated that hERGIa subunits are a major component of channels producing the ventricular repolarizing current lKr, thus explaining the underlying cause of LQTS-2 as a loss or reduction of lKr. Most recently, we have identified another subunit of !Kr channels, hERG1b. Encoded by an alternate transcript of the hERG1 gene, hERG1b is identical to hERG1a except for its amino terminus, which is highly divergent. This proposal explores mechanisms by which the differences in the amino termini specify heteromeric assembly, export from the endoplasmic reticulum and stability within the plasma membrane. In addition, we propose to characterize a mutation found in an unmapped LQTS patient potentially representing the first disease mutation specific to hERG1b. These studies are expected to provide novel insights into mechanisms of potassium channel assembly as well as the molecular mechanisms of cardiac arrhythmias.
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