α-Synuclein plasma membrane localization correlates with cellular phosphatidylinositol polyphosphate levels.

Reeba Susan Jacob,Philipp Selenko,Davide Mercadante,Alessandro Dema,Cédric Eichmann

doi:10.7554/elife.61951

Abstract

The Parkinson's disease protein α-synuclein (αSyn) promotes membrane fusion and fission by interacting with various negatively charged phospholipids. Despite postulated roles in endocytosis and exocytosis, plasma membrane (PM) interactions of αSyn are poorly understood. Here, we show that phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidylinositol 3,4,5-trisphosphate (PIP3), two highly acidic components of inner PM leaflets, mediate PM localization of endogenous pools of αSyn in A2780, HeLa, SK-MEL-2, and differentiated and undifferentiated neuronal SH-SY5Y cells. We demonstrate that αSyn binds to reconstituted PIP2 membranes in a helical conformation in vitro and that PIP2 synthesizing kinases and hydrolyzing phosphatases reversibly redistribute αSyn in cells. We further delineate that αSyn-PM targeting follows phosphoinositide-3 kinase (PI3K)-dependent changes of cellular PIP2 and PIP3 levels, which collectively suggests that phosphatidylinositol polyphosphates contribute to αSyn's function(s) at the plasma membrane.

Highlights

Aggregates of human a-synuclein constitute the main components of Lewy body inclusions in Parkinson’s disease (PD) and other synucleinopathies (Goedert et al, 2013)
Our results establish that clusters of endogenous aSyn are found at the plasma membrane (PM) of human A2780, HeLa, SK-MEL-2 and SH-SY5Y cells, where their abundance correlates with PIP2 levels (Figure 1)
We show that targeted overexpression of the PIP2-generating kinase phosphatidylinositol 4-phosphate 5-kinase type Ig (PIPKIg) increases aSyn at the PM (Figure 1E), whereas the PIP2-specific phosphatase INPP5E reduces the amount of PM aSyn (Figure 3A)

Summary

Introduction

Aggregates of human a-synuclein (aSyn) constitute the main components of Lewy body inclusions in Parkinson’s disease (PD) and other synucleinopathies (Goedert et al, 2013). ASyn is abundantly found in different types of neurons, where it primarily localizes to presynaptic terminals and regulates synaptic vesicle (SV) clustering and trafficking (Sulzer and Edwards, 2019). Isolated aSyn is disordered in solution, whereas residues 1–100 adopt extended or kinked helical conformations upon binding to membranes containing negatively charged phospholipids (Fusco et al, 2018). ASyn oligomers bind to and disrupt cellular and reconstituted membranes (Reynolds et al, 2011; Fusco et al, 2017), whereas mature aggregates are found closely associated with membranous cell structures and intact organelles in cellular models of Lewy body inclusions (Mahul-Mellier et al, 2020) and in postmortem brain sections of PD patients (Shahmoradian et al, 2019)

Methods

Results

Conclusion