Ion channels underlie the rapid and diverse electrical signaling in neurons that enables complex organisms to sense and react to their environment, move, learn, communicate and problem-solve in a highly sophisticated manner. The diverse range of voltage-gated potassium (Kv) currents expressed in the brain is essential for signal processing and integration in neuronal circuits. High frequency, temporally precise firing in auditory neurons requires potassium channels formed by Kv3.1, characterized by rapid gating and activation at relatively depolarized potentials. Auditory neurons of Kv3.1 knockout mice are unable to follow high frequency stimulation, a model for hearing loss in the high-frequency range in humans. Dynamic regulation of Kv3.1 current properties is thought to modulate the firing frequency of auditory neurons in response to different stimulus frequencies. We recently found that Kv3.1 forms complexes with MiRP2, a single transmembrane domain channel ancillary subunit, in mammalian brain. Further, MiRP2 and related subunits MinK and MiRP1 modify Kv3.1 gating properties, slowing their activation and deactivation and altering voltage dependence, current density and inactivation. We now propose to investigate whether MiRPs can associate with Kv3.1 channels in auditory neurons, whether MiRPs regulate Kv3.1 trafficking, and which aspects of Kv3.1 regulation by MiRPs could underlie Kv3.1 current heterogeneity in auditory neurons, and thus wide-frequency auditory perception.
Our Specific Aims are: 1. Determine the ability of MinK, MiRP1 and MiRP2 to form complexes with Kv3.1 alpha subunits in auditory neurons. 2. Determine the ability of MinK, MiRP1 and MiRP2 to mediate dynamin-dependent internalization of Kv3.1 alpha subunits. 3. Examine the predicted effects in auditory neurons of MiRP modulation of Kv3.1, Kv3.3 and Kv3.1-Kv3.3 channels using a combination of heterologous coexpression experiments and computer simulations.
