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

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.

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

Nature Communications ◽

10.1038/s41467-021-25281-4 ◽

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.

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

10.1101/2021.04.07.438431 ◽

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.

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

10.1101/2020.07.09.196154 ◽

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.

Download Full-text