Differential regulation of wild-type and mutant alpha-synuclein binding to synaptic membranes by cytosolic factors.
BACKGROUND
Alpha-Synuclein (alpha-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 alpha-syn gene are associated with rare autosomal dominant forms of familial PD. However, the regulation of alpha-syn's cellular localization in neurons and the effects of the PD-linked mutations are poorly understood.


RESULTS
In the present study, we analysed the ability of cytosolic factors to regulate alpha-syn binding to synaptic membranes. We show that co-incubation with brain cytosol significantly increases the membrane binding of normal and PD-linked mutant alpha-syn. To characterize cytosolic factor(s) that modulate alpha-syn binding properties, we investigated the ability of proteins, lipids, ATP and calcium to modulate alpha-syn membrane interactions. We report that lipids and ATP are two of the principal cytosolic components that modulate Wt and A53T alpha-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 alpha-syn interaction with synaptic membrane. In addition, the impaired membrane binding observed for A30P alpha-syn was significantly mitigated by the presence of protease-sensitive factors in brain cytosol.


CONCLUSIONS
These findings suggest that endogenous brain cytosolic factors regulate Wt and mutant alpha-syn membrane binding, and could represent potential targets to influence alpha-syn solubility in brain.
Wislet-Gendebien
Sabine
S
Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Ontario, M5S 3H2 Canada. s.wislet@ulg.ac.be
Visanji
Naomi P
NP
Whitehead
Shawn N
SN
Marsilio
Diana
D
Hou
Weimin
W
Figeys
Daniel
D
Fraser
Paul E
PE
Bennett
Steffany A L
SA
Tandon
Anurag
A
D000255:Adenosine Triphosphate / Q000032:analysis / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D001923:Brain Chemistry; D002118:Calcium / Q000032:analysis / Q000378:metabolism; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism*; D005838:Genotype; D006801:Humans; D008055:Lipids / Q000032:analysis; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D020125:Mutation, Missense; D010300:Parkinson Disease / Q000235:genetics / Q000378:metabolism; D010972:Platelet Activating Factor / Q000031:analogs & derivatives / Q000032:analysis / Q000378:metabolism; D011485:Protein Binding; D013570:Synaptic Membranes / Q000378:metabolism*; D013574:Synaptosomes / Q000378:metabolism; D051844:alpha-Synuclein / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*
D008055:Lipids; D008565:Membrane Proteins; D010972:Platelet Activating Factor; D051844:alpha-Synuclein; C037145:1-hexadecyl-2-acetyl-glycero-3-phosphocholine; D000255:Adenosine Triphosphate; D002118:Calcium