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Recent cloning of K(+) channel β subunits revealed that these cytoplasmic polypeptides can dramatically alter the kinetics of current inactivation and promote efficient glycosylation and surface expression of the channel-forming α subunits. Here, we examined the expression, distribution, and association of two of these β subunits, Kvβ1 and Kvβ2, in adult rat brain. In situhybridization using cRNA probes revealed that these β-subunit genes are heterogeneously expressed, with high densities of Kvβ1 mRNA in the striatum, CA1 subfield of the hippocampus, and cerebellar Purkinje cells, and high densities of Kvβ2 mRNA in the cerebral cortex, cerebellum, and brainstem. Immunohistochemical staining using subunit-specific monoclonal and affinity-purified polyclonal antibodies revealed that the Kvβ1 and Kvβ2 polypeptides frequently co-localize and are concentrated in neuronal perikarya, dendrites, and terminal fields, and in the juxtaparanodal region of myelinated axons. Immunoblot and reciprocal co-immunoprecipitation analyses indicated that Kvβ2 is the major β subunit present in rat brain membranes, and that most K(+) channel complexes containing Kvβ1 also contain Kvβ2. Taken together, these data suggest that Kvβ2 is a component of almost all K(+)channel complexes containing Kv1 α subunits, and that individual channels may contain two or more biochemically and functionally distinct β-subunit polypeptides.
Rhodes et al. (Thu,) studied this question.