title: Cellular mechanisms of mutations in Kv7.1: auditory functions in Jervell and Lange-Nielsen syndrome vs. Romano-Ward syndrome.
abstract: As a result of cell-specific functions of voltage-activated K(+) channels, such as Kv7.1, mutations in this channel produce profound cardiac and auditory defects. At the same time, the massive diversity of K(+) channels allows for compensatory substitution of mutant channels by other functional channels of their type to minimize defective phenotypes. Kv7.1 represents a clear example of such functional dichotomy. While several point mutations in the channel result in a cardio-auditory syndrome called Jervell and Lange-Nielsen syndrome (JLNS), about 100-fold mutations result in long QT syndrome (LQTS) denoted as Romano-Ward syndrome (RWS), which has an intact auditory phenotype. To determine whether the cellular mechanisms for the diverse phenotypic outcome of Kv7.1 mutations, are dependent on the tissue-specific function of the channel and/or specialized functions of the channel, we made series of point mutations in hKv7.1 ascribed to JLNS and RWS. For JLNS mutations, all except W248F yielded non-functional channels when expressed alone. Although W248F at the end of the S4 domain yielded a functional current, it underwent marked inactivation at positive voltages, rendering the channel non-functional. We demonstrate that by definition, none of the JLNS mutants operated in a dominant negative (DN) fashion. Instead, the JLNS mutants have impaired membrane trafficking, trapped in the endoplasmic reticulum (ER) and Cis-Golgi. The RWS mutants exhibited varied functional phenotypes. However, they can be summed up as exhibiting DN effects. Phenotypic differences between JLNS and RWS may stem from tissue-specific functional requirements of cardiac vs. inner ear non-sensory cells.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Center for Neuroscience, School of Medicine, University of California, Davis Davis, CA, USA.
authors.forename: Atefeh
authors.initials: A
authors.lastname: Mousavi Nik
authors.affiliation: Department of Anesthesiology and Pain Medicine, Center for Neuroscience, School of Medicine, University of California, Davis Davis, CA, USA.
authors.forename: Somayeh
authors.initials: S
authors.lastname: Gharaie
authors.affiliation: Department of Anesthesiology and Pain Medicine, Center for Neuroscience, School of Medicine, University of California, Davis Davis, CA, USA.
authors.forename: Hyo
authors.initials: H
authors.lastname: Jeong Kim
keywords: genetic diseases; hearing loss; membrane trafficking; mutant; potassium channels