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The first N-terminal amino acids of alpha-synuclein are essential for alpha-helical structure formation in vitro and membrane binding in yeast.

ABSTRACT: Alpha-synuclein (alpha-syn), a protein implicated in Parkinson's disease, is structurally diverse. In addition to its random-coil state, alpha-syn can adopt an alpha-helical structure upon lipid membrane binding or a beta-sheet structure upon aggregation. We used yeast biology and in vitro biochemistry to detect how sequence changes alter the structural propensity of alpha-syn. The N-terminus of the protein, which adopts an alpha-helical conformation upon lipid binding, is essential for membrane binding in yeast, and variants that are more prone to forming an alpha-helical structure in vitro are generally more toxic to yeast. beta-Sheet structure and inclusion formation, on the other hand, appear to be protective, possibly by sequestering the protein from the membrane. Surprisingly, sequential deletion of residues 2 through 11 caused a dramatic drop in alpha-helical propensity, vesicle binding in vitro, and membrane binding and toxicity in yeast, part of which could be mimicked by mutating aspartic acid at position 2 to alanine. Variants with distinct structural preferences, identified here by a reductionist approach, provide valuable tools for elucidating the nature of toxic forms of alpha-syn in neurons.

SUBMITTER: Vamvaca K

PROVIDER: S-EPMC2801807 | biostudies-literature | 2009 Jun

REPOSITORIES: biostudies-literature

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The first N-terminal amino acids of alpha-synuclein are essential for alpha-helical structure formation in vitro and membrane binding in yeast.

Vamvaca Katherina K Volles Michael J MJ Lansbury Peter T PT

Journal of molecular biology 20090313 2

Alpha-synuclein (alpha-syn), a protein implicated in Parkinson's disease, is structurally diverse. In addition to its random-coil state, alpha-syn can adopt an alpha-helical structure upon lipid membrane binding or a beta-sheet structure upon aggregation. We used yeast biology and in vitro biochemistry to detect how sequence changes alter the structural propensity of alpha-syn. The N-terminus of the protein, which adopts an alpha-helical conformation upon lipid binding, is essential for membrane ...[more]

PMID: 19285989

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Project description:The misfolding and fibrillization of the protein, α-synuclein (αsyn), is associated with neurodegenerative disorders referred to as the synucleinopathies. Understanding the mechanisms of αsyn misfolding is an important area of interest given that αsyn misfolding contributes to disease pathogenesis. While many studies report the ability of synthetic lipid membranes to modulate αsyn folding, there is little data pertaining to the mechanism(s) of this interaction. αSyn has previously been shown to associate with small lipid vesicles released by cells called extracellular vesicles (EVs) and it is postulated these interactions may assist in the spreading of pathological forms of this protein. Together, this presents the need for robust characterisation studies on αsyn fibrillization using biologically-derived vesicles. In this study, we comprehensively characterised the ability of lipid-rich small extracellular vesicles (sEVs) to alter the misfolding of αsyn induced using the Protein Misfolding Cyclic Amplification (PMCA) assay. The biochemical and biophysical properties of misfolded αsyn were examined using a range of techniques including: Thioflavin T fluorescence, transmission electron microscopy, analytical centrifugation and western immunoblot coupled with protease resistance assays and soluble/insoluble fractionation. We show that sEVs cause an acceleration in αsyn fibrillization and provide comprehensive evidence that this results in an increase in the abundance of mature insoluble fibrillar species. In order to elucidate the relevance of the lipid membrane to this interaction, sEV lipid membranes were modified by treatment with methanol, or a combination of methanol and sarkosyl. These treatments altered the ultrastructure of the sEVs without changing the protein cargo. Critically, these modified sEVs had a reduced ability to influence αsyn fibrillization compared to untreated counterparts. This study reports the first comprehensive examination of αsyn:EV interactions and demonstrates that sEVs are powerful modulators of αsyn fibrillization, which is mediated by the sEV membrane. In doing so, this work provides strong evidence for a role of sEVs in contributing directly to αsyn misfolding in the synucleinopathy disorders.

Dataset Information

The first N-terminal amino acids of alpha-synuclein are essential for alpha-helical structure formation in vitro and membrane binding in yeast.

Publications

The first N-terminal amino acids of alpha-synuclein are essential for alpha-helical structure formation in vitro and membrane binding in yeast.

Similar Datasets

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