Identification of a cytoplasmic domain important in the polarized expression and clustering of the Kv2.1 K⁺ channel

The voltage-sensitive K⁺ channel Kv2.1 has a polarized and clustered distribution in neurons. To investigate the basis for this localization, we expressed wild-type Kv2.1 and two COOH-terminal truncation mutants, ΔC318 and ΔC187, in polarized epithelial MDCK cells. These functional channel proteins had differing subcellular localization, in that while both wild- type Kv2.1 and ΔC187 localized to the lateral membrane in high density clusters, ΔC318 was expressed uniformly on both apical and lateral membranes. A chimeric protein containing the hemagglutin in protein from influenza virus and the region of Kv2.1 that differentiates the two truncation mutants (amino acids 536-666) was also expressed in MDCK cells, where it was found in high density clusters similar to those observed for Kv2.1. Polarized expression and clustering of Kv2.1 correlates with detergent solubility, suggesting that interaction with the detergent insoluble cytoskeleton may be necessary for proper localization of this channel.