Molecular and cellular correlates in Kv channel clustering: entropy-based regulation of cluster ion channel density

Limor Lewin,Esraa Nsasra,Uzi Hadad,Ella Golbary,Irit Orr,Ofer Yifrach

doi:10.1038/s41598-020-68003-4

Limor Lewin, Esraa Nsasra + Show 4 more

Open Access

https://doi.org/10.1038/s41598-020-68003-4

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Journal: Scientific Reports	Publication Date: Jul 9, 2020
Citations: 7	License type: open-access

Affiliation: Ben-Gurion University of the Negev

Abstract

Scaffold protein-mediated ion channel clustering at unique membrane sites is important for electrical signaling. Yet, the mechanism(s) by which scaffold protein-ion channel interactions lead to channel clustering or how cluster ion channel density is regulated is mostly not known. The voltage-activated potassium channel (Kv) represents an excellent model to address these questions as the mechanism underlying its interaction with the post-synaptic density 95 (PSD-95) scaffold protein is known to be controlled by the length of the extended ‘ball and chain’ sequence comprising the C-terminal channel region. Here, using sub-diffraction high-resolution imaging microscopy, we show that Kv channel ‘chain’ length regulates Kv channel density with a ‘bell’-shaped dependence, reflecting a balance between thermodynamic considerations controlling ‘chain’ recruitment by PSD-95 and steric hindrance due to the spatial proximity of multiple channel molecules. Our results thus reveal an entropy-based mode of channel cluster density regulation that mirrors the entropy-based regulation of the Kv channel-PSD-95 interaction. The implications of these findings for electrical signaling are discussed.

Highlights

Scaffold protein-mediated ion channel clustering at unique membrane sites is important for electrical signaling
Our study revealed that Kv channel ‘chain’ length regulates cluster Kv channel membrane density with a ‘bell’-shaped dependence, reflecting the balance between steric hindrance and thermodynamic considerations controlling ‘chain’ recruitment by the post-synaptic density 95 (PSD-95) scaffold protein
Confocal imaging microscopy was previously used to describe Kv channel clustering in several heterologous expression systems[12,14,16]. Such studies focused on identifying the binding determinants of the Kv channel and post-synaptic density (PSD)-95 variants that are important for channel cell surface expression and clustering

Summary

Introduction

Scaffold protein-mediated ion channel clustering at unique membrane sites is important for electrical signaling. According to the ‘ball and chain’ mechanism that describes this interaction, the random walk motion of the unstructured C-terminal channel ‘chain’, bearing a conserved six amino acid PDZ-binding motif (the ‘ball’) at its tip, recruits the PSD-95 scaffold protein partner (Fig. 1a)[16,17] in a manner analogous to the role of the N-terminal tail in regulating channel fast inactivation[18]. Evidence supporting this mechanism primarily relies on the ‘chain’-length. Such modulation has important implications for electrical signaling in the nervous system

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