Pharmacological characteristics of Kv1.1- and Kv1.2-containing channels are influenced by the stoichiometry and positioning of their α subunits

Abstract

Voltage-sensitive neuronal Kv1 channels composed of four α subunits and four associated auxiliary β subunits control neuronal excitability and neurotransmission. Limited information exists on the combinations of α subunit isoforms (i.e. Kv1.1-1.6) or their positions in the oligomers, and how these affect sensitivity to blockers. It is known that TEA (tetraethylammonium) inhibits Kv1.1 channels largely due to binding a critical tyrosine (Tyr379) in the pore, whereas Val381 at the equivalent location in Kv1.2 makes it insensitive. With the eventual aim of developing blockers for therapeutic purposes, Kv1.1 and 1.2 α subunit genes were concatenated to form combinations representing those in central neurons, followed by surface expression in HEK (human embryonic kidney)-293 cells as single-chain functional proteins. Patch-clamp recordings demonstrated the influences of the ratios and positioning of these α subunits on the biophysical and pharmacological properties of oligomeric K+ channels. Raising the ratio of Kv1.1 to Kv1.2 in Kv1.2-1.2-1.1-1.2 led to the resultant channels being more sensitive to TEA and also affected their biophysical parameters. Moreover, mutagenesis of one or more residues in the first Kv1.2 to resemble those in Kv1.1 increased TEA sensitivity only when it is adjacent to a Kv1.1 subunit, whereas placing a non-interactive subunit between these two diminished susceptibility. The findings of the present study support the possibility of α subunits being precisely arranged in Kv1 channels, rather than being randomly assembled. This is important in designing drugs with abilities to inhibit particular oligomeric Kv1 subtypes, with the goal of elevating neuronal excitability and improving neurotransmission in certain diseases.