Association of β-catenin with the α-subunit of neuronal large-conductance Ca2+-activated K+ channels

The association of Ca2+-activated K+ channels with voltage-gated Ca2+ channels at the presynaptic active zones of hair cells, photoreceptors, and neurons contributes to rapid repolarization of the membrane after excitation. Ca2+ channels have been shown to bind to a large set of synaptic proteins, but the proteins interacting with Ca2+-activated K+ channels remain unknown. Here, we report that the large-conductance Ca2+-activated K+ channel of the chicken's cochlear hair cell interacts with beta-catenin. Yeast two-hybrid assays identified the S10 region of the K+ channel's alpha-subunit and the ninth armadillo repeat and carboxyl terminus of beta-catenin as necessary for the interaction. An antiserum directed against the a-subunit specifically coprecipitated beta-catenin from brain synaptic proteins. beta-Catenin is known to associate with the synaptic protein Lin7/Velis/MALS, whose interaction partner Lin2/CASK also binds voltage-gated Ca2+ channels. beta-Catenin may therefore provide a physical link between the two types of channels at the presynaptic active zone.