SCIENCE@home

Kv2 potassium channels form endoplasmic reticulum/plasma membrane junctions via interaction with VAPA and VAPB

Ben Johnson,Ashley N Leek,Laura Solé,Emily E Maverick,T. Levine,M. Tamkun

Published 2018 in Proceedings of the National Academy of Sciences of the United States of America

ABSTRACT

Significance In addition to functioning as a delayed-rectifier K+ channel, Kv2.1 interacts with the cortical endoplasmic reticulum (ER) in hippocampal neurons to form somatic ER/plasma membrane (ER/PM) junctions. Neuronal activity and insult induce Kv2.1 release from the cortical ER and subsequent ER withdrawal from the PM. Neuronal ER/PM contacts represent >10% of the cell surface and play roles in membrane trafficking, the regulation of burst firing, Ca2+ homeostasis, and control of PM lipid. We report here that Kv2 channel–VAMP-associated protein (VAP) interaction tethers the cortical ER to the PM via a noncanonical FFAT motif contained within the channel C terminus. Since VAPs have a wide-ranging interactome, Kv2-induced ER remodeling and VAP concentration at ER/PM contacts likely play a central role in neuronal physiology. Kv2.1 exhibits two distinct forms of localization patterns on the neuronal plasma membrane: One population is freely diffusive and regulates electrical activity via voltage-dependent K+ conductance while a second one localizes to micrometer-sized clusters that contain densely packed, but nonconducting, channels. We have previously established that these clusters represent endoplasmic reticulum/plasma membrane (ER/PM) junctions that function as membrane trafficking hubs and that Kv2.1 plays a structural role in forming these membrane contact sites in both primary neuronal cultures and transfected HEK cells. Clustering and the formation of ER/PM contacts are regulated by phosphorylation within the channel C terminus, offering cells fast, dynamic control over the physical relationship between the cortical ER and PM. The present study addresses the mechanisms by which Kv2.1 and the related Kv2.2 channel interact with the ER membrane. Using proximity-based biotinylation techniques in transfected HEK cells we identified ER VAMP-associated proteins (VAPs) as potential Kv2.1 interactors. Confirmation that Kv2.1 and -2.2 bind VAPA and VAPB employed colocalization/redistribution, siRNA knockdown, and Förster resonance energy transfer (FRET)-based assays. CD4 chimeras containing sequence from the Kv2.1 C terminus were used to identify a noncanonical VAP-binding motif. VAPs were first identified as proteins required for neurotransmitter release in Aplysia and are now known to be abundant scaffolding proteins involved in membrane contact site formation throughout the ER. The VAP interactome includes AKAPs, kinases, membrane trafficking machinery, and proteins regulating nonvesicular lipid transport from the ER to the PM. Therefore, the Kv2-induced VAP concentration at ER/PM contact sites is predicted to have wide-ranging effects on neuronal cell biology.

PUBLICATION RECORD

CITATION MAP

EXTRACTION MAP

CLAIMS

  • No claims are published for this paper.

CONCEPTS

  • No concepts are published for this paper.

REFERENCES

Showing 1-65 of 65 references · Page 1 of 1

CITED BY

Showing 1-100 of 159 citing papers · Page 1 of 2

12
Next