Stim2-Eb3 Association and Morphology of Dendritic Spines in Hippocampal Neurons

Ekaterina Pchitskaya,Elena Popugaeva,Daria Chernyuk,Nina Kraskovskaya,Olga Vlasova,Hua Zhang,Ilya Bezprozvanny

doi:10.1038/s41598-017-17762-8

Abstract

Mushroom spines form strong synaptic contacts and are essential for memory storage. We have previously demonstrated that neuronal store-operated calcium entry (nSOC) in hippocampal neurons is regulated by STIM2 protein. This pathway plays a key role in stability of mushroom spines and is compromised in different mice models of Alzheimer’s disease (AD). Actin was thought to be the sole cytoskeleton compartment presented in dendritic spines, however, recent studies demonstrated that dynamic microtubules with EB3 capped plus-ends transiently enter spines. We showed that STIM2 forms an endoplasmic reticulum (ER) Ca2+ -dependent complex with EB3 via Ser-x-Ile-Pro aminoacid motif and that disruption of STIM2-EB3 interaction resulted in loss of mushroom spines in hippocampal neurons. Overexpression of EB3 causes increase of mushroom spines fraction and is able to restore their deficiency in hippocampal neurons obtained from PS1-M146V-KI AD mouse model. STIM2 overexpression failed to restore mushroom dendritic spines after EB3 knockdown, while in contrast EB3 overexpression rescued loss of mushroom spines resulting from STIM2 depletion. We propose that EB3 is involved in regulation of dendritic spines morphology, in part due to its association with STIM2, and that modulation of EB3 expression is a potential way to overcome synaptic loss during AD.

Highlights

Store-operated calcium entry is controlled by Stromal interacting molecules (STIMs) – an endoplasmic reticulum (ER) calcium sensor proteins, containing amino-terminal EF-hand Ca2+ -binding domain located in the ER lumen[18]
The results obtained in our experiments demonstrate that EB3 interacts with STIM2 and that this interaction promotes formation of mushroom spines in hippocampal neurons
We discovered that EB2 protein is highly enriched in soma in comparison to dendrites, whereas EB3 is broadly expressed in both soma and dendrites (Fig. 1A)

Summary

Introduction

Store-operated calcium entry is controlled by Stromal interacting molecules (STIMs) – an endoplasmic reticulum (ER) calcium sensor proteins, containing amino-terminal EF-hand Ca2+ -binding domain located in the ER lumen[18]. Functional studies of nSOC in hippocampal neurons suggested a critical role of Orai[1] channels[28]. The role of STIM1 in control of neuronal L-type Ca2+ channel activity[31] and feedback regulation of Ca2+ signals in presynaptic terminals was reported[32]. Consistent with important role played by STIM1 and STIM2 in neurons, learning and memory phenotypes were observed following knockout or overexpression of these proteins[30,33,34]. In case of AD, overexpression of nSOC component STIM2 prevents mushroom spine loss in AD mouse models and in conditions of amyloid toxicity suggesting that downregulation of STIM2-nSOC pathway is a potential mechanism of synaptic loss in AD14,15,17. Our findings open a new potential way of stabilizing synaptic spines in AD

Methods

Results

Conclusion