scholarly journals AMPA receptor anchoring at CA1 synapses is determined by N-terminal domain and TARP γ8 interactions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jake F. Watson ◽  
Alexandra Pinggera ◽  
Hinze Ho ◽  
Ingo H. Greger
Keyword(s):  
Ampa Receptor ◽  
Hippocampal Slices ◽  
Super Resolution ◽  
Synaptic Cleft ◽  
Information Storage ◽  
Excitatory Synapses ◽  
Terminal Domain ◽  
Hippocampal Ca1 ◽  
Interaction Domains ◽  
Resolution Imaging

AbstractAMPA receptor (AMPAR) abundance and positioning at excitatory synapses regulates the strength of transmission. Changes in AMPAR localisation can enact synaptic plasticity, allowing long-term information storage, and is therefore tightly controlled. Multiple mechanisms regulating AMPAR synaptic anchoring have been described, but with limited coherence or comparison between reports, our understanding of this process is unclear. Here, combining synaptic recordings from mouse hippocampal slices and super-resolution imaging in dissociated cultures, we compare the contributions of three AMPAR interaction domains controlling transmission at hippocampal CA1 synapses. We show that the AMPAR C-termini play only a modulatory role, whereas the extracellular N-terminal domain (NTD) and PDZ interactions of the auxiliary subunit TARP γ8 are both crucial, and each is sufficient to maintain transmission. Our data support a model in which γ8 accumulates AMPARs at the postsynaptic density, where the NTD further tunes their positioning. This interplay between cytosolic (TARP γ8) and synaptic cleft (NTD) interactions provides versatility to regulate synaptic transmission and plasticity.

scholarly journals AMPA receptor anchoring at CA1 synapses is determined by an interplay of N-terminal domain and TARP γ8 interactions

2020 ◽  
Author(s):  
Jake F. Watson ◽  
Alexandra Pinggera ◽  
Hinze Ho ◽  
Ingo H. Greger
Keyword(s):  
Ampa Receptor ◽  
Super Resolution ◽  
Synaptic Cleft ◽  
Information Storage ◽  
Excitatory Synapses ◽  
Terminal Domain ◽  
Hippocampal Ca1 ◽  
Interaction Domains ◽  
Resolution Imaging

AbstractAMPA receptor (AMPAR) abundance and positioning at excitatory synapses regulates the strength of transmission. Changes in AMPAR localisation can enact synaptic plasticity, allowing long-term information storage, and is therefore tightly controlled. Multiple mechanisms regulating AMPAR synaptic anchoring have been described, but with limited coherence or comparison between reports, our understanding of this process is unclear. Here, combining synaptic recordings and super-resolution imaging, we compare the contributions of three AMPAR interaction domains controlling transmission at hippocampal CA1 synapses. We show that the AMPAR C-termini play only a modulatory role, whereas the extracellular N-terminal domain (NTD) and PDZ interactions of the auxiliary subunit TARP γ8 are both crucial, and each is sufficient to maintain transmission. Our data support a model in which γ8 accumulates AMPARs at the postsynaptic density, where the NTD further tunes their positioning. This interplay between cytosolic (γ8) and synaptic cleft (NTD) interactions provides versatility to regulate synaptic transmission and plasticity.

scholarly journals Astrocyte-secreted IL-33 mediates homeostatic synaptic plasticity in the adult hippocampus

2020 ◽  
Vol 118 (1) ◽  
pp. e2020810118
Author(s):  
Ye Wang ◽  
Wing-Yu Fu ◽  
Kit Cheung ◽  
Kwok-Wang Hung ◽  
Congping Chen ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Neuronal Activity ◽  
Hippocampal Slices ◽  
Memory Formation ◽  
Conditional Knockout ◽  
Acute Administration ◽  
Excitatory Synapses ◽  
Homeostatic Synaptic Plasticity ◽  
Hippocampal Ca1

Hippocampal synaptic plasticity is important for learning and memory formation. Homeostatic synaptic plasticity is a specific form of synaptic plasticity that is induced upon prolonged changes in neuronal activity to maintain network homeostasis. While astrocytes are important regulators of synaptic transmission and plasticity, it is largely unclear how they interact with neurons to regulate synaptic plasticity at the circuit level. Here, we show that neuronal activity blockade selectively increases the expression and secretion of IL-33 (interleukin-33) by astrocytes in the hippocampal cornu ammonis 1 (CA1) subregion. This IL-33 stimulates an increase in excitatory synapses and neurotransmission through the activation of neuronal IL-33 receptor complex and synaptic recruitment of the scaffold protein PSD-95. We found that acute administration of tetrodotoxin in hippocampal slices or inhibition of hippocampal CA1 excitatory neurons by optogenetic manipulation increases IL-33 expression in CA1 astrocytes. Furthermore, IL-33 administration in vivo promotes the formation of functional excitatory synapses in hippocampal CA1 neurons, whereas conditional knockout of IL-33 in CA1 astrocytes decreases the number of excitatory synapses therein. Importantly, blockade of IL-33 and its receptor signaling in vivo by intracerebroventricular administration of its decoy receptor inhibits homeostatic synaptic plasticity in CA1 pyramidal neurons and impairs spatial memory formation in mice. These results collectively reveal an important role of astrocytic IL-33 in mediating the negative-feedback signaling mechanism in homeostatic synaptic plasticity, providing insights into how astrocytes maintain hippocampal network homeostasis.

scholarly journals The postsynaptic MAGUK scaffold protein MPP2 organises a distinct interactome that incorporates GABAA receptors at the periphery of excitatory synapses

2020 ◽  
Author(s):  
Bettina Schmerl ◽  
Niclas Gimber ◽  
Benno Kuropka ◽  
Jakob Rentsch ◽  
Stella-Amrei Kunde ◽  
...  
Keyword(s):  
Protein Complexes ◽  
Super Resolution ◽  
Scaffold Protein ◽  
Excitatory Synapses ◽  
The Novel ◽  
Glutamatergic Synapses ◽  
Receptor Associated Protein ◽  
Resolution Imaging ◽  
Scaffold Molecule ◽  
Inhibitory Regulation

AbstractRecent advances in imaging technology have highlighted that scaffold proteins and receptors are arranged in sub-synaptic nanodomains. The synaptic MAGUK scaffold protein MPP2 is a component of AMPA receptor-associated protein complexes and also binds to the synaptic cell adhesion molecule SynCAM1. Using super-resolution imaging, we now show that MPP2 and SynCAM1 are situated at the periphery of the postsynaptic density. In order to explore MPP2-associated protein complexes, we used a quantitative comparative mass spectrometry approach and identified multiple GABAA receptor subunits among the novel synaptic MPP2 interactors. We further show that GABAA receptors are found together with MPP2 in a subset of dendritic spines and thus highlight MPP2 as a scaffold molecule capable of acting as an adaptor molecule that links peripheral synaptic elements critical for inhibitory regulation to central structures at the PSD of glutamatergic synapses.

scholarly journals Engineering paralog-specific PSD-95 synthetic binders as potent and minimally invasive imaging probes

2021 ◽  
Author(s):  
Charlotte Rimbault ◽  
Christelle Breillat ◽  
Benjamin Compans ◽  
Estelle Toulmé ◽  
Filipe Nunes Vicente ◽  
...  
Keyword(s):  
Fluorescence Imaging ◽  
Imaging Techniques ◽  
Super Resolution ◽  
Specific Protein ◽  
Scaffold Proteins ◽  
Excitatory Synapses ◽  
Protein Activity ◽  
Imaging Probes ◽  
Resolution Imaging ◽  
Endogenous Proteins

Despite the constant advances in fluorescence imaging techniques, monitoring endogenous proteins still constitutes a major challenge in particular when considering dynamics studies or super-resolution imaging. We have recently evolved specific protein-based binders for PSD-95, the main postsynaptic scaffold proteins at excitatory synapses. Since the synthetic binders recognize epitopes not directly involved in the target protein activity, we consider them here as tools to develop endogenous PSD-95 imaging probes. After confirming their lack of impact on PSD-95 function, we validated their use as intrabody fluorescent probes. We further engineered the probes and demonstrated their usefulness in different super-resolution imaging modalities (STED, PALM and DNA-PAINT) in both live and fixed neurons. Finally, we exploited the binders to enrich at the synapse genetically encoded calcium reporters. Overall, we demonstrate that these evolved binders constitute a robust and efficient platform to selectively target and monitor endogenous PSD-95 using various fluorescence imaging techniques.

scholarly journals Super-resolution imaging of synaptic and Extra-synaptic AMPA receptors with different-sized fluorescent probes

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Sang Hak Lee ◽  
Chaoyi Jin ◽  
En Cai ◽  
Pinghua Ge ◽  
Yuji Ishitsuka ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Ampa Receptor ◽  
Fluorescent Probes ◽  
Ampa Receptors ◽  
Fluorescent Dyes ◽  
Super Resolution ◽  
Ampar Trafficking ◽  
Resolution Imaging ◽  
20 Nm ◽  
Super Resolution Microscopy

Previous studies tracking AMPA receptor (AMPAR) diffusion at synapses observed a large mobile extrasynaptic AMPAR pool. Using super-resolution microscopy, we examined how fluorophore size and photostability affected AMPAR trafficking outside of, and within, post-synaptic densities (PSDs) from rats. Organic fluorescent dyes (≈4 nm), quantum dots, either small (≈10 nm diameter; sQDs) or big (>20 nm; bQDs), were coupled to AMPARs via different-sized linkers. We find that >90% of AMPARs labeled with fluorescent dyes or sQDs were diffusing in confined nanodomains in PSDs, which were stable for 15 min or longer. Less than 10% of sQD-AMPARs were extrasynaptic and highly mobile. In contrast, 5–10% of bQD-AMPARs were in PSDs and 90–95% were extrasynaptic as previously observed. Contrary to the hypothesis that AMPAR entry is limited by the occupancy of open PSD ‘slots’, our findings suggest that AMPARs rapidly enter stable ‘nanodomains’ in PSDs with lifetime >15 min, and do not accumulate in extrasynaptic membranes.

scholarly journals Synaptic transmission and plasticity require AMPA receptor anchoring via its N-terminal domain

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Jake F Watson ◽  
Hinze Ho ◽  
Ingo H Greger
Keyword(s):  
Synaptic Transmission ◽  
Signal Transmission ◽  
Hippocampal Slices ◽  
Synaptic Cleft ◽  
Long Term Potentiation ◽  
Terminal Domain ◽  
Term Potentiation ◽  
A Subunit ◽  
Excitatory Neurotransmission ◽  
Activity Dependent

AMPA-type glutamate receptors (AMPARs) mediate fast excitatory neurotransmission and are selectively recruited during activity-dependent plasticity to increase synaptic strength. A prerequisite for faithful signal transmission is the positioning and clustering of AMPARs at postsynaptic sites. The mechanisms underlying this positioning have largely been ascribed to the receptor cytoplasmic C-termini and to AMPAR-associated auxiliary subunits, both interacting with the postsynaptic scaffold. Here, using mouse organotypic hippocampal slices, we show that the extracellular AMPAR N-terminal domain (NTD), which projects midway into the synaptic cleft, plays a fundamental role in this process. This highly sequence-diverse domain mediates synaptic anchoring in a subunit-selective manner. Receptors lacking the NTD exhibit increased mobility in synapses, depress synaptic transmission and are unable to sustain long-term potentiation (LTP). Thus, synaptic transmission and the expression of LTP are dependent upon an AMPAR anchoring mechanism that is driven by the NTD.

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