Subcellular localization of hippocampal ryanodine receptor 2 and its role in neuronal excitability and memory

Florian Hiess,Adam Institoris,Lina Chen,Grant R Gordon,Anutosh Ganguly,Henk E D J Ter Keurs,Junting Huang,Ruiwu Wang,Gerald W Zamponi,Peter K Stys,Bo Sun,Zhenpeng Song,Zizhen Zhang,Jinjing Yao,John Paul Estillore,S R Wayne Chen

doi:10.1038/s42003-022-03124-2

Florian Hiess, Adam Institoris + Show 14 more

Open Access

https://doi.org/10.1038/s42003-022-03124-2

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Abstract

Ryanodine receptor 2 (RyR2) is abundantly expressed in the heart and brain. Mutations in RyR2 are associated with both cardiac arrhythmias and intellectual disability. While the mechanisms of RyR2-linked arrhythmias are well characterized, little is known about the mechanism underlying RyR2-associated intellectual disability. Here, we employed a mouse model expressing a green fluorescent protein (GFP)-tagged RyR2 and a specific GFP probe to determine the subcellular localization of RyR2 in hippocampus. GFP-RyR2 was predominantly detected in the soma and dendrites, but not the dendritic spines of CA1 pyramidal neurons or dentate gyrus granular neurons. GFP-RyR2 was also detected within the mossy fibers in the stratum lucidum of CA3, but not in the presynaptic terminals of CA1 neurons. An arrhythmogenic RyR2-R4496C+/− mutation downregulated the A-type K+ current and increased membrane excitability, but had little effect on the afterhyperpolarization current or presynaptic facilitation of CA1 neurons. The RyR2-R4496C+/− mutation also impaired hippocampal long-term potentiation, learning, and memory. These data reveal the precise subcellular distribution of hippocampal RyR2 and its important role in neuronal excitability, learning, and memory.

Highlights

Ryanodine receptor 2 (RyR2) is abundantly expressed in the heart and brain
These data indicate that the Alexa Fluor 647 (AF647)-labeled MBPGBP fusion protein is a highly specific probe for green fluorescent protein (GFP)-RyR2, and that RyR2 is abundantly expressed in hippocampal CA1 and dentate gyrus (DG) neurons
We determined the subcellular distribution of RyR2 in hippocampus and assessed the impact of the catecholaminergic polymorphic ventricular tachycardia (CPVT) RyR2 R4496C+/− mutation on neuronal activity, neuronal excitability, long-term potentiation (LTP), learning and memory

Summary

Introduction

Ryanodine receptor 2 (RyR2) is abundantly expressed in the heart and brain. Mutations in RyR2 are associated with both cardiac arrhythmias and intellectual disability. It has been shown that RyRs are expressed in different compartments in hippocampal neurons, including presynaptic terminals, dendritic spines, dendritic shafts, and the soma[6,13–17] Consistent with these subcellular localizations of RyRs, functional studies have implicated an important role of RyRs in synaptic transmission, long-term potentiation (LTP), synaptic plasticity, and gene expression[14,18–26]. The precise subcellular localization and roles of the RyR2 isoform in different compartments (presynaptic terminals, dendritic spines, dendritic shafts, and the soma) in hippocampal neurons are largely undefined. This is due, in part, to the presence of all three RyR isoforms in hippocampal neurons, the uncertain antibody specificity in the context of whole brain tissue, and the lack of isoform-specific functional probes for RyR2. CA1 pyramidal and DG granular neurons and the functional consequences of a CPVT RyR2 mutation in neuronal excitability and cognitive function

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