RETRACTED ARTICLE: Differential regulation of wild-type and mutant alpha-synuclein binding to synaptic membranes by cytosolic factors

Sabine Wislet-Gendebien,Weimin Hou,Shawn N Whitehead,Naomi P Visanji,Anurag Tandon,Steffany Al Bennett,Paul E Fraser,Diana Marsilio,Daniel Figeys

doi:10.1186/1471-2202-9-92

Abstract

BackgroundAlpha-Synuclein (α-syn), a 140 amino acid protein associated with presynaptic membranes in brain, is a major constituent of Lewy bodies in Parkinson's disease (PD). Three missense mutations (A30P, A53T and E46K) in the α-syn gene are associated with rare autosomal dominant forms of familial PD. However, the regulation of α-syn's cellular localization in neurons and the effects of the PD-linked mutations are poorly understood.ResultsIn the present study, we analysed the ability of cytosolic factors to regulate α-syn binding to synaptic membranes. We show that co-incubation with brain cytosol significantly increases the membrane binding of normal and PD-linked mutant α-syn. To characterize cytosolic factor(s) that modulate α-syn binding properties, we investigated the ability of proteins, lipids, ATP and calcium to modulate α-syn membrane interactions. We report that lipids and ATP are two of the principal cytosolic components that modulate Wt and A53T α-syn binding to the synaptic membrane. We further show that 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (C16:0 PAF) is one of the principal lipids found in complex with cytosolic proteins and is required to enhance α-syn interaction with synaptic membrane. In addition, the impaired membrane binding observed for A30P α-syn was significantly mitigated by the presence of protease-sensitive factors in brain cytosol.ConclusionThese findings suggest that endogenous brain cytosolic factors regulate Wt and mutant α-syn membrane binding, and could represent potential targets to influence α-syn solubility in brain.

Highlights

Alpha-Synuclein (α-syn), a 140 amino acid protein associated with presynaptic membranes in brain, is a major constituent of Lewy bodies in Parkinson's disease (PD)
To identify novel co-factors of α-syn binding to presynaptic membranes, we assessed whether co-incubation with brain cytosol modifies α-syn's interaction with mem
Our assay measured the binding of recombinant human α-syn purified from E. coli to synaptic membranes prepared from brains of α-syn-deficient (KO) mice, in the presence or absence of brain cytosol derived from α-syndeficient mice (Figure 1A)

Summary

Introduction

Alpha-Synuclein (α-syn), a 140 amino acid protein associated with presynaptic membranes in brain, is a major constituent of Lewy bodies in Parkinson's disease (PD). Α-Syn behaves as a peripherally associated membrane protein and can stably interact with synthetic phospholipid vesicles containing negatively charged head groups [3] via its amino-terminal domain, an amphipathic region comprising almost twothirds of the protein and containing seven copies of an 11residue repeat sequence [4]. Whereas the freely diffusible form of α-syn is natively unfolded, the N-terminal repeat region adopts an α-helical conformation upon binding to artificial vesicles and detergent micelles [3]. Numerous studies have revealed that the interaction of α-syn with phospholipid membranes, fatty acids, or detergent micelles alters the kinetics of its aggregation [4,5,6,7,8,9]. Despite the understanding of the conformational properties of membrane-bound α-syn, the biochemical mechanisms that mediate α-syn interaction with biological membranes are poorly understood, thereby limiting our understanding of α-syn's physiological role, as well as potential therapeutic approaches to moderate its misfolding and aggregation in disease

Methods

Results

Discussion

Conclusion