Non-microtubule tubulin-based backbone and subordinate components of postsynaptic density lattices.

Tatsuo Suzuki,Nobuo Terada,Tsutomu Kai,Shigeki Higashiyama,Mamoru Honda,Katsuhiko Tabuchi,Yoshinori Shirai,Weidong Li,Kiyokazu Kametani

doi:10.26508/lsa.202000945

Abstract

A purification protocol was developed to identify and analyze the component proteins of a postsynaptic density (PSD) lattice, a core structure of the PSD of excitatory synapses in the central nervous system. "Enriched"- and "lean"-type PSD lattices were purified by synaptic plasma membrane treatment to identify the protein components by comprehensive shotgun mass spectrometry and group them into minimum essential cytoskeleton (MEC) and non-MEC components. Tubulin was found to be a major component of the MEC, with non-microtubule tubulin widely distributed on the purified PSD lattice. The presence of tubulin in and around PSDs was verified by post-embedding immunogold labeling EM of cerebral cortex. Non-MEC proteins included various typical scaffold/adaptor PSD proteins and other class PSD proteins. Thus, this study provides a new PSD lattice model consisting of non-microtubule tubulin-based backbone and various non-MEC proteins. Our findings suggest that tubulin is a key component constructing the backbone and that the associated components are essential for the versatile functions of the PSD.

Highlights

Structural changes in postsynaptic density (PSD) are important mechanisms for maintaining synaptic plasticity, the basis for memory and learning (Bosch et al, 2014)
The amount of protein recovered in PSD lattice (PSDL) (1% OG, U) and PSDL (1% OG, B), PSDL preparations purified by the new method, were 12.9 ± 0.84 and 4.9 ± 1.95 μg, respectively, from 3 mg of synaptic plasma membrane (SPM) protein
We investigated the localization of tubulin molecules on the PSDL structure in PSDL (1% OG) using immunogold negativestaining EM

Summary

Introduction

Structural changes in postsynaptic density (PSD) are important mechanisms for maintaining synaptic plasticity, the basis for memory and learning (Bosch et al, 2014). The molecular mechanism underlying PSD remodeling is not currently known, the role of actin dynamics in spine morphology is well known (Sekino et al, 2007; Bosch et al, 2014; Spence & Soderling, 2015). A complete understanding of the structure of PSD is indispensable to fully elucidate the molecular mechanisms of spine and PSD dynamics during the expression of synaptic plasticity. We purified a PSD lattice (PSDL) structure and proposed “PSDL-based dynamic nanocolumn” model for the molecular architecture of PSD. In this model, the scaffold protein model and the PSDL model are combined (Suzuki et al, 2018). Whole components could not be identified by SDS–PAGE and Western blotting

Results

Discussion

Conclusion