# Regulation of Kv2.1 Channels by Kv9.1 Variants

## TL;DR

This study explores how a genetic variant in the Kv9.1 protein affects the function of Kv2.1 potassium channels in neurons, potentially explaining increased pain sensitivity in some individuals.

## Contribution

The study reveals that a specific Kv9.1 variant reduces surface expression of Kv2.1 channels more strongly than the wild-type variant, possibly explaining pain hypersensitivity.

## Key findings

- Kv9.1Val reduces surface expression of Kv2.1 channels more than Kv9.1Ile in HeLa cells and neurons.
- Both Kv9.1 variants cause a hyperpolarizing shift in Kv2.1 channel activation and inactivation.
- Kv9.1Val and Kv9.1Ile co-localize with Kv2.1 at the cell surface despite ER retention when expressed alone.

## Abstract

Background/Objectives: Kv2 channels have important conducting and nonconducting functions and are regulated by their co-assembly with ‘silent’ Kv subunits, including Kv9.1. Kv9.1 is co-expressed with Kv2 channels in sensory neurons, and a common allele that changes Ile489 to Val in human Kv9.1 is associated with pain hypersensitivity in patients. The mechanism responsible for this association remains unknown, but we hypothesise that these two variants differ in their regulation of Kv2.1 properties, and this is what we set out to test. Methods: Expression was carried out using HEK293 cells, OHeLa cells, and primary cultures of hippocampal neurons, and the biophysical and trafficking properties of homomeric and heteromeric channels were assessed by confocal fluorescence microscopy and patch clamp analysis. Results: Both Kv9.1Ile and Kv9.1Val were retained within the endoplasmic reticulum when expressed individually, but when co-expressed with Kv2.1, they co-localised with Kv2.1 within the surface clusters. Both variants reduced the surface expression of Kv2.1 channels and the size of channel clusters, with Kv9.1Val producing a greater reduction in surface expression in both the HeLa cells and neurons. They both caused a similar hyperpolarising shift in the voltage dependence of channel activation and inactivation. Concatamers of Kv2.1 and Kv9.1 suggested that both 3:1 and 2:2 ratios of Kv2.1 to Kv9.1 were permitted, although 2:2 resulted in lower surface expression and function. Conclusions: The Ile489Val substitution in Kv9.1 does not disrupt its ability to co-assemble with Kv2 channels, nor its effects on the voltage-dependence of channel gating, but it did produce a greater reduction in the Kv2.1 surface expression, suggesting that this underlies its association with pain hypersensitivity.