TY - JOUR

T1 - The effects of alpha-synuclein on phospholipid vesicle integrity

T2 - a study using 31P NMR and electron microscopy

AU - Madine, Jillian

AU - Hughes, Eleri

AU - Doig, Andrew J

AU - Middleton, David A

PY - 2008/9

Y1 - 2008/9

N2 - Associations between the 140 amino acid protein alpha-synuclein (asyn) and presynaptic vesicles may play a role in maintaining synaptic plasticity and neurotransmitter release. These physiological processes may involve disruption and fusion of vesicles, arising from interactions between specific regions of asyn, including the highly basic N-terminal domain, and the surface of vesicles. This work investigates whether asyn affects the integrity of model unilamellar vesicles of varying size and phospholipid composition, by monitoring paramagnetic Mn(2+)-induced broadening of peaks in the (31)P nuclear magnetic resonance spectrum of the lipid head groups. It is shown that asyn increases the permeability to Mn(2+) of both large (200 nm diameter) and small (50 nm diameter) vesicles composed of zwitterionic phosphatidylcholine and anionic phosphatidylglycerol at protein/lipid molar ratios as low as 1:2000. Further experiments on peptides corresponding to sequences in the N-terminal (10-48), C-terminal (120-140) and central hydrophobic (71-82) regions of asyn suggest that single regions of the protein are capable of permeabilizing the vesicles to varying extents. Electron micrographs of the vesicles after addition of asyn indicate that the enhanced permeability is coupled to large-scale disruption or fusion of the vesicles. These results indicate that asyn is able to permeabilize phospholipid vesicles at low relative concentrations, dependent upon the properties of the vesicles. This could have implications for asyn playing a role in vesicle synthesis, maintenance and fusion within synapses.

AB - Associations between the 140 amino acid protein alpha-synuclein (asyn) and presynaptic vesicles may play a role in maintaining synaptic plasticity and neurotransmitter release. These physiological processes may involve disruption and fusion of vesicles, arising from interactions between specific regions of asyn, including the highly basic N-terminal domain, and the surface of vesicles. This work investigates whether asyn affects the integrity of model unilamellar vesicles of varying size and phospholipid composition, by monitoring paramagnetic Mn(2+)-induced broadening of peaks in the (31)P nuclear magnetic resonance spectrum of the lipid head groups. It is shown that asyn increases the permeability to Mn(2+) of both large (200 nm diameter) and small (50 nm diameter) vesicles composed of zwitterionic phosphatidylcholine and anionic phosphatidylglycerol at protein/lipid molar ratios as low as 1:2000. Further experiments on peptides corresponding to sequences in the N-terminal (10-48), C-terminal (120-140) and central hydrophobic (71-82) regions of asyn suggest that single regions of the protein are capable of permeabilizing the vesicles to varying extents. Electron micrographs of the vesicles after addition of asyn indicate that the enhanced permeability is coupled to large-scale disruption or fusion of the vesicles. These results indicate that asyn is able to permeabilize phospholipid vesicles at low relative concentrations, dependent upon the properties of the vesicles. This could have implications for asyn playing a role in vesicle synthesis, maintenance and fusion within synapses.

KW - Liposomes

KW - Magnetic Resonance Spectroscopy

KW - Manganese

KW - Membrane Fusion

KW - Microscopy, Electron

KW - Models, Biological

KW - Peptide Fragments

KW - Permeability

KW - Phosphatidylcholines

KW - Phosphatidylglycerols

KW - Phospholipids

KW - Phosphorus Isotopes

KW - Synapses

KW - alpha-Synuclein

U2 - 10.1080/09687680802467977

DO - 10.1080/09687680802467977

M3 - Journal article

C2 - 18949627

VL - 25

SP - 518

EP - 527

JO - Molecular Membrane Biology

JF - Molecular Membrane Biology

SN - 1464-5203

IS - 6-7

ER -