Bidirectional protein–protein interactions control liquid–liquid phase separation of PSD-95 and its interaction partners

Nikolaj Riis Christensen,Christian Parsbæk Pedersen,Vita Sereikaite,Jannik Nedergaard Pedersen,Maria Vistrup-Parry,Andreas Toft Sørensen,Daniel Otzen,Kaare Teilum,Kenneth Lindegaard Madsen,Kristian Strømgaard

doi:10.1016/j.isci.2022.103808

Nikolaj Riis Christensen, Christian Parsbæk Pedersen + Show 8 more

Open Access

https://doi.org/10.1016/j.isci.2022.103808

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Journal: iScience	Publication Date: Jan 25, 2022
Citations: 6	License type: cc-by

Affiliation: Aarhus University, University of Copenhagen

Abstract

SummaryThe organization of the postsynaptic density (PSD), a protein-dense semi-membraneless organelle, is mediated by numerous specific protein–protein interactions (PPIs) which constitute a functional postsynapse. The PSD protein 95 (PSD-95) interacts with a manifold of proteins, including the C-terminal of transmembrane AMPA receptor (AMPAR) regulatory proteins (TARPs). Here, we uncover the minimal essential peptide responsible for the Stargazin (TARP-γ2)-mediated liquid–liquid phase separation (LLPS) formation of PSD-95 and other key protein constituents of the PSD. Furthermore, we find that pharmacological inhibitors of PSD-95 can facilitate the formation of LLPS. We found that in some cases LLPS formation is dependent on multivalent interactions, while in other cases short, highly charged peptides are sufficient to promote LLPS in complex systems. This study offers a new perspective on PSD-95 interactions and their role in LLPS formation, while also considering the role of affinity over multivalency in LLPS systems.

Highlights

Synaptic transmission is dependent on the proper function and anchoring of ligand-gated ion channels such as the a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs), which are responsible for the majority of fast excitatory transmission in the CNS
We find that pharmacological inhibitors of postsynaptic density (PSD)-95 can facilitate the formation of LLPS
This study offers a new perspective on PSD-95 interactions and their role in LLPS formation, while considering the role of affinity over multivalency in LLPS systems

Summary

Introduction

Synaptic transmission is dependent on the proper function and anchoring of ligand-gated ion channels such as the a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs), which are responsible for the majority of fast excitatory transmission in the CNS. There are a number of lead candidates targeting PSD-95 in both preclinical and clinical development (Christensen et al, 2019), covering both small molecules (Florio et al, 2009; Hu et al, 2013; Lee et al, 2015; Wu et al, 2014) and in particular, peptide-derived compounds (Bach et al, 2009, 2011, 2012; Long et al, 2003; Nissen et al, 2015; Piserchio et al, 2004; Sainlos et al, 2011; Aarts et al, 2002), all of which target the PDZ domains of PSD-95 These molecules feature both monovalent and multivalent interactions with PSD-95, and their affinities range from micromolar (Florio et al, 2009; Piserchio et al, 2004; Aarts et al, 2002) to low nanomolar (Bach et al, 2009, 2012; Nissen et al, 2015)

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