Association of beta-catenin with the alpha-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 β-catenin. Yeast two-hybrid assays identified the S10 region of the K⁺ channel's α-subunit and the ninth armadillo repeat and carboxyl terminus of β-catenin as necessary for the interaction. An antiserum directed against the α-subunit specifically coprecipitated β-catenin from brain synaptic proteins. β-Catenin is known to associate with the synaptic protein Lin7/Velis/MALS, whose interaction partner Lin2/CASK also binds voltage-gated Ca²⁺ channels. β-Catenin may therefore provide a physical link between the two types of channels at the presynaptic active zone.