Association and colocalization of the Kvβ1 and Kvβ2 β-subunits with Kv1 α-subunits in mammalian brain K⁺ channel complexes

The differential expression and association of cytoplasmic β-subunits with pore-forming α-subunits may contribute significantly to the complexity and heterogeneity of voltage-gated K⁺ channels in excitable cells. Here we examined the association and colocalization of two mammalian β-subunits, Kvβ1 and Kvβ2, with the K⁺ channel α-subunits Kv1.1, Kv1.2, Kv1.4, Kv1.6, and Kv2.1 in adult rat brain. Reciprocal coimmunoprecipitation experiments using subunit-specific antibodies indicated that Kvβ1 and Kvβ2 associate with all the Kv1 α-subunits examined and with each other, but not with Kv2.1. A much larger portion of the total brain pool Kv1-containing channel complexes was found associated with Kvβ2 than with Kvβ1. Single- and multiple-label immunohistochemical staining indicated that Kvβ1 codistributes extensively with Kv1.1 and Kv1.4 in cortical interneurons, in the hippocampal perforant path and mossy fiber pathways, and in the globus pallidus and substantia nigra. Kvβ2 codistributes extensively with Kv1.1 and Kv1.2 in all brain regions examined and was strikingly colocalized with these α-subunits in the juxtaparanodal region of nodes of Ranvier as well as in the axons and terminals of cerebellar basket cells. Taken together, these data provide a direct demonstration that Kvβ1 and Kvβ2 associate and colocolize with Kv1 α-subunits in native tissues and provide a biochemical and neuroanatomical basis for the differential contribution of Kv1 α- and β-subunits to electrophysiologically diverse neuronal K⁺ currents.