Assembly, Secretory Pathway Trafficking, and Surface Delivery of Kainate Receptors Is Regulated by Neuronal Activity

Ashley J Evans,Sonam Gurung,Kevin A Wilkinson,David J Stephens,Jeremy M Henley

doi:10.1016/j.celrep.2017.06.001

Abstract

SummaryIonotropic glutamate receptor (iGluR) trafficking and function underpin excitatory synaptic transmission and plasticity and shape neuronal networks. It is well established that the transcription, translation, and endocytosis/recycling of iGluRs are all regulated by neuronal activity, but much less is known about the activity dependence of iGluR transport through the secretory pathway. Here, we use the kainate receptor subunit GluK2 as a model iGluR cargo to show that the assembly, early secretory pathway trafficking, and surface delivery of iGluRs are all controlled by neuronal activity. We show that the delivery of de novo kainate receptors is differentially regulated by modulation of GluK2 Q/R editing, PKC phosphorylation, and PDZ ligand interactions. These findings reveal that, in addition to short-term regulation of iGluRs by recycling/endocytosis and long-term modulation by altered transcription/translation, the trafficking of iGluRs through the secretory pathway is under tight activity-dependent control to determine the numbers and properties of surface-expressed iGluRs.

Highlights

The morphological complexity of neurons presents unique challenges for the timely and appropriate supply of proteins to dynamic and metabolically active synapses
Using retention using selective hooks (RUSH) to Assay ionotropic glutamate receptor (iGluR) Secretory Pathway Trafficking We utilized the RUSH system by tagging the GluK2 KAR subunit and both the GluA1 and GluA2 AMPAR subunits at the N terminus with a streptavidin-binding peptide (SBP) and a fluorescent tag
When these constructs are coexpressed with a streptavidin-KDEL ‘‘hook’’ that localizes to the lumen of the endoplasmic reticulum (ER), the SBP-tagged subunits are anchored at the ER membrane (Figure 1A)

Summary

Introduction

The morphological complexity of neurons presents unique challenges for the timely and appropriate supply of proteins to dynamic and metabolically active synapses. Relatively little is known about whether and how the delivery of newly synthesized iGluRs through the secretory pathway is controlled by neuronal activity. Transmembrane proteins with an immature glycosylation profile can be surfaceexpressed, suggesting that not all secretory pathway cargo needs to be processed within the Golgi prior to plasma membrane insertion (Hanus et al, 2016)

Results

Discussion

Conclusion