| Endocochlear potential (EP) (>80 mV) is required for normal sound transduction and generated in part by the high K+ throughput across the apical membrane of basal cells (BC) and intermediate cells (IC) of the stria vascularis (StV). The importance of Cl- channels in the inner ear is demonstrated by the fact that mutations in barttin, an auxillary subunit of Cl- channel ClC-K, results in Bartter's Syndrome of which deafness is a component. The goals of this work are to determine the cellular/molecular, structural, and functional mechanisms by which K + and Cl- channels contribute towards the generation of EP.;We employed the use of total internal reflection fluorescence (TIRF) to selectively illuminate ClC-K and barttin GFP fusion proteins in the plasma membranes of Xenopus laevis oocytes. We found that the mature channel is expressed in a stoichiometry of two ClC-K subunits to one barttin subunit. This further confirms barttin's speculative role in channel trafficking to the membrane, as only one barttin is necessary for robust expression. Fluorescence Resonance Energy Transfer (FRET) analysis was also employed to further delineate the expression pattern and stoichiometric properties of the channel.;For the generation of EP, a high-throughput of K+ across ICs and BCs of the StV is essential to maintain the ∼80 mV "batttery" necessary for hair cell transduction. We cloned the ERG1a potassium channel in the mouse inner ear (MERG1a) and studied its cellular distribution in the cochlear using immunostaining. We characterized the channel activity in mouse StV using whole cell recording, two-electrode voltage clamp, and single-channel recording. We propose that the merg K+ channel is a likely candidate for establishing the high throughout of K+ ions across ICs to generate EP. Thus, we present an additional role for the channel in K+ cycling in the inner ear. |
