Organizing neuronal ER-PM junctions is a conserved nonconducting function of Kv2 plasma membrane ion channels

Abstract

27Endoplasmic reticulum (ER) and plasma membrane (PM) form junctions crucial to ion and lipid 28 signaling and homeostasis. The Kv2.1 ion channel is unique among PM proteins in organizing 29 ER-PM junctions. Here, we show that this organizing function is conserved between Kv2 family 30 members that differ in their biophysical properties, modulation and cellular expression. 31Manipulation of actin cytoskeleton surrounding Kv2 ER-PM junctions affects their spatial 32 organization. Kv2-containing ER-PM junctions overlap with those formed by canonical ER-PM 33 tethers. ER-PM junction organization by Kv2 channels is unchanged by point mutations that 34 eliminate ion conduction, but abolished by those that eliminate PM clustering without impacting 35 ion channel function. Kv2.2 is distinct in lacking the reversible modulation of junction organization 36 present in Kv2.1. Brain neurons in Kv2 double knockout mice have altered ER-PM junctions, 37 demonstrating a conserved in vivo function for Kv2 family members distinct from their canonical 38 role as ion-conducting channels shaping neuronal excitability. 39 40. CC-BY 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/296731 doi: bioRxiv preprint first posted online Apr. 6, 2018; 3 Introduction 41Membrane contacts between the endoplasmic reticulum (ER) and plasma membrane (PM), or 42 ER-PM junctions, are a ubiquitous feature of eukaryotic cells (1-4). These specialized sites at 43 which ER is held in close apposition (10-30 nm) and other excitable and non-excitable cell types. In brain neurons, Kv2 channels are distinct from 63 other Kv channels (17) in being specifically localized to high-density micron sized clusters 64 prominent on the soma, proximal dendrites, and axon initial segment (34-42). Kv2 channels also 65 form such clusters when exogenously expressed in cultured neurons and in heterologous cells 66 . CC-BY 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint (which . http://dx.doi.org/10.1101/296731 doi: bioRxiv preprint first posted online Apr. 6, 2018; 4 (35, 37, 39, 41-47 at/near RyR clusters in specific neuron types, including hippocampal CA1 pyramidal neurons and 114 layer 6 neocortical neurons (Figure 1). A similar juxtaposition of Kv2.2 and RyR clusters was seen 115 in CHNs (Figure 1). In these classes of neurons, Kv2.2 was often found coclustered with Kv2.1 at 116 these ER-PM junctions (Figure 1). Neurons in each preparation also contained RyR clusters that 117 did not appear to colocalize with Kv2.2 or Kv2.1 (Figure 1). These findings demonstrate that Kv2.2 118 . CC-BY 4.0 International license It is made available under a was not peer-reviewed) is the author/funder, who has granted ...

Kv2 potassium channels meet VAP

“…The association of K + channels with the ER may provide a functional link between these channels and Ca 2+ dynamics. This may occur either through the presence of RyRs or of voltagedependent PM Ca 2+ (CaV1.2) channels at the same ER-PM contacts (14,18). Because a large fraction of the Kv2 channels are thought to be in a nonconducting state, and more so the population of the channels accumulated at ER-PM contacts, it is also possible that these channels may have a nonconducting role that impacts some function of the ER, or of ER-anchored proteins.…”