Effects of Detergent on α-Synuclein Structure: A Native MS-Ion Mobility Study

Abstract

The intrinsically disordered protein α-synuclein plays a major role in Parkinson’s disease. The protein can oligomerize resulting in the formation of various aggregated species in neuronal cells, leading to neurodegeneration. The interaction of α-synuclein with biological cell membranes plays an important role for specific functions of α-synuclein monomers, e.g., in neurotransmitter release. Using different types of detergents to mimic lipid molecules present in biological membranes, including the presence of Ca2+ ions as an important structural factor, we aimed to gain an understanding of how α-synuclein interacts with membrane models and how this affects the protein conformation and potential oligomerization. We investigated detergent binding stoichiometry, affinity and conformational changes of α-synuclein taking detergent concentration, different detergent structures and charges into account. With native nano-electrospray ionization ion mobility-mass spectrometry, we were able to detect unique conformational patterns resulting from binding of specific detergents to α-synuclein. Our data demonstrate that α-synuclein monomers can interact with detergent molecules irrespective of their charge, that protein-micelle interactions occur and that micelle properties are an important factor.

Taking Charge: Metal Ions Accelerate Amyloid Aggregation in Sequence Variants of α-Synuclein

“…The amyloid precursor protein alpha-synuclein (αS) is structurally defined as an intrinsically disordered protein (IDP) and visits a large and diverse conformational space, including partially compact and extended states . Aggregation and self-assembly of αS into β-sheet rich amyloid fibril structures is associated with the onset of Parkinson’s disease (PD) and other synucleopathies. , The neuropathology of PD is characterized by the deposition of insoluble cellular inclusions called Lewy Bodies (LB) in dopaminergic neurons in the substantia nigra of the brain. , The composition of LBs consists of fibrillar αS, lipids, mitochondria, metal ions, and various other cellular components. − Monomeric αS is found in vivo to partition between the cytoplasm and phospholipid membranes. − Although the exact functional role(s) of αS remain uncertain, localization of αS to presynaptic nerve terminals suggests a role in vesicle binding, clustering, and neurotransmitter release. − This proposed function relies on the lipid binding properties of αS which are governed by the charge distribution across the protein sequence. − …”

The role of solvation on the conformational landscape of α-synuclein

“…11 n-IM/MS has been successfully applied to characterizing α-synuclein (αSN), which is a disordered monomer in solution at pH 7 and low concentrations. 23 For instance, the effects of pH, 24 small molecule binding, 25 metal binding, [26][27][28] and the presence of membrane mimics 29 on the α-synuclein conformational ensemble have all been characterized by n-IM/MS.…”

Developments in Trapped Ion Mobility Mass Spectrometry to Probe the Early Stages of Peptide Aggregation

“…Various IM-MS studies focus on protein and peptide aggregates, highlighting the possibilities to use IM-MS to determine the structure of those assemblies ,− to characterize their formation ,, or even monitor their dynamics. − Moreover, IM-MS can also be applied to probe the interaction with molecules that influence the aggregation process, − despite the nature of the transient oligomeric phase. Even though these experiments have brought more insight in the aggregation processes that coincide with the development of the neurodegenerative diseases, many important details on the exact sequence of these events remain still unclear.…”