Subunit Composition of Kv1 Channels in Human CNS

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Abstract
: The α subunits of Shaker-related K+ channels (Kv1.X) show characteristic distributions in mammalian brain and restricted coassembly. Despite the functional importance of these voltage-sensitive K+ channels and involvement in a number of diseases, little progress has been achieved in deciphering the subunit composition of the (α)4(β)4 oligomers occurring in human CNS. Thus, the association of α and β subunits was investigated in cerebral grey and white matter and spinal cord from autopsy samples. Immunoblotting established the presence of Kv1.1, 1.2, and 1.4 in all the tissues, with varying abundance. Sequential immunoprecipitations identified the subunits coassembled. A putative tetramer of Kv1.3/1.4/1.1/1.2 was found in grey matter. Both cerebral white matter and spinal cord contained the heterooligomers Kv1.1/1.4 and Kv1.1/1.2, similar to grey matter, but both lacked Kv1.3 and the Kv1.4/1.2 combination. An apparent Kv1.4 homooligomer was detected in all the samples, whereas only the brain tissue possessed a putative Kv1.2 homomer. In grey matter, Kvβ2.1 was coassociated with the Kv1.1/1.2 combination and Kv1.2 homooligomer. In white matter, Kvβ2.1 was associated with Kv1.2 only, whereas Kvβ1.1 coprecipitated with all the α subunits present. This represents the first description of Kv1 subunit complexes in the human CNS and demonstrates regional variations, indicative of functional specialisation.