Molecular Determinants of Kv1.3 Potassium Channels-induced Proliferation

Laura Jiménez-Pérez,Pilar Cidad,Inés Álvarez-Miguel,Alba Santos-Hipólito,Rebeca Torres-Merino,Esperanza Alonso,Miguel Ángel De La Fuente,José Ramón López-López,M Teresa Pérez-García

doi:10.1074/jbc.m115.678995

Abstract

Changes in voltage-dependent potassium channels (Kv channels) associate to proliferation in many cell types, including transfected HEK293 cells. In this system Kv1.5 overexpression decreases proliferation, whereas Kv1.3 expression increases it independently of K(+) fluxes. To identify Kv1.3 domains involved in a proliferation-associated signaling mechanism(s), we constructed chimeric Kv1.3-Kv1.5 channels and point-mutant Kv1.3 channels, which were expressed as GFP- or cherry-fusion proteins. We studied their trafficking and functional expression, combining immunocytochemical and electrophysiological methods, and their impact on cell proliferation. We found that the C terminus is necessary for Kv1.3-induced proliferation. We distinguished two residues (Tyr-447 and Ser-459) whose mutation to alanine abolished proliferation. The insertion into Kv1.5 of a sequence comprising these two residues increased proliferation rate. Moreover, Kv1.3 voltage-dependent transitions from closed to open conformation induced MEK-ERK1/2-dependent Tyr-447 phosphorylation. We conclude that the mechanisms for Kv1.3-induced proliferation involve the accessibility of key docking sites at the C terminus. For one of these sites (Tyr-447) we demonstrated the contribution of MEK/ERK-dependent phosphorylation, which is regulated by voltage-induced conformational changes.

Highlights

In this study we undertook the molecular dissection of the Kv1.3 channel and the parallel changes observed in HEK proliferation to conclude with an attractive hypothesis aimed to understand the role of ion channels in cell proliferation
The opposite effect on cell proliferation of two channels of the same subfamily (Kv1.3 and Kv1.5) has been of seminal importance for accomplishing our goals. This antithetical role has been described in different cell lineages, including VSMCs, oligodendrocyte progenitor cells, and microglia (10 –13, 21)
The fact that these antagonist effects on cell proliferation could still be observed upon heterologous expression of the channels represented an opportunity to explore the molecular mechanisms that associate the expression of these channels with the changes in the rate of proliferation

Summary

Introduction

These experiments suggest that the molecular determinants for the effect of the channels on cell proliferation are contained in their C-terminal domain. Despite the increased current density there were no significant changes on the effect on HEK cells proliferation (Fig. 3C).

Results

Conclusion