Ion channel proteins in mouse and human vestibular tissue

Abstract

Background and objective: Electrical activity in hair cells and neurons of the inner ear is necessary for the transduction and modulation of stimuli that impinge on the cochlea and vestibular endorgans of the inner ear. The underlying basis of this activity is pore-forming proteins in the membrane of excitable cells that allow the influx and efflux of various ions, including Na + , Ca 2+ , and K + , among others. These channels are critical to both electrical activity as well as the development of excitable cells because they may initiate long-term signals that are important in the maintenance and survival of these cells. We investigated the expression of several Shaker potassium ion channel proteins and an accessory beta subunit in the vestibular endorgans of mouse and human.

Methods: Vestibular tissue consisting of cristae ampullares was harvested from adult and neonatal mice as well as from human subjects undergoing vestibular surgery. Western blot analysis and immunoprecipitation were used to identify the presence or absence, in mouse, of alpha subunits Kv1.2, Kv1.4, and Kv1.5 and of beta subunit Kvbeta1.1 in mouse. Coimmunoprecipitation was used to identify interactions between alpha and beta subunits. Immunohistochemistry was used to localize Kv1.2 in mouse and human tissues.

Results: The presence of Kvalpha1.2 and Kvbeta1.1 was confirmed in adult mouse crista ampullaris by Western blotting. Coimmunoprecipitation experiments showed that Kv1.2 and Kvbeta1.1 interact in these tissues. Immunostaining localized Kv1.2 to regions within and extraneous to the sensory epithelium of mouse and human cristae ampullares. In comparison, Kv1.4 and Kv1.5 were not found in the crista ampullaris.

Conclusions: We describe the presence, location, and interaction of various potassium ion channel alpha subunits and a beta subunit. These data are initial descriptions of potassium ion channels in the mammalian vestibular system and begin to provide an understanding of the protein subunits that form ion channels of the mammalian inner ear. In addition, our data show that there are interactions that occur that may regulate the biophysical properties of these channels, thereby contributing to the diversity of channel function. This knowledge is critical to understanding the genes that encode these channels and finding cures for pathologies of hearing and balance.

Significance: We detail initial characteristics of potassium ion channel proteins including alpha subunits Kv1.2, Kv1.4, and Kv1.5 and beta subunit Kvbeta1.1 in mammalian vestibular tissue. This knowledge is critical to understanding the processing of vestibular stimuli and the regulation of endolymphatic function. Mutations of ion channels can cause neurological pathologies including auditory and vestibular disorders in humans.