Silencing of the Tandem Pore Domain Halothane-inhibited K+ Channel 2 (THIK2) Relies on Combined Intracellular Retention and Low Intrinsic Activity at the Plasma Membrane

Description

The tandem pore domain halothane-inhibited K channel 1(THIK1) produces background K currents. Despite 62% aminoacid identity with THIK1, THIK2 is not active upon heterologous expression. Here, we show that this apparent lack of activity is due to a unique combination of retention in the endoplasmic reticulum and low intrinsic channel activity at the plasmamembrane. A THIK2 mutant containing a proline residue(THIK2-A155P) in its second inner helix (M2) produces K-selective currents with properties similar to THIK1, includinginhibition by halothane and insensitivity to extracellular pHvariations. Another mutation in the M2 helix (I158D) furtherincreases channel activity and affects current kinetics. We alsoshow that the cytoplasmic amino-terminal region of THIK2 (NtTHIK2) contains an arginine-rich motif (RRSRRR) that acts as aretention/retrieval signal. Mutation of this motif in THIK2induces a relocation of the channel to the plasma membrane,resulting in measurable currents, even in the absence of mutations in the M2 helix. Cell surface delivery of a Nt-THIK2-CD161 chimera is increased by mutating the arginines of theretention motif but also by converting the serine embedded inthis motif to aspartate, suggesting a phosphorylation-dependent regulation of THIK2 trafficking.

Abstract

International audience

Additional details