Interaction of human alpha-Synuclein and Parkinson's disease variants with phospholipids. Structural analysis using site-directed mutagenesis.
alpha-Synuclein has been centrally implicated in neurodegenerative disease, and a normal function in developmental synaptic plasticity has been suggested by studies in songbirds. A variety of observations suggest the protein partitions between membrane and cytosol, a behavior apparently conferred by a conserved structural similarity to the exchangeable apolipoproteins. Here we show that the capacity to bind lipids is broadly distributed across exons 3, 4, and 5 (encoding residues 1-102). Binding to phosphatidylserine-containing vesicles requires the presence of all three exons, while binding to phosphatidic acid can be mediated by any one of the three. Consistent with a "class A2" helical binding mechanism, lipid association is disrupted by introduction of charged residues along the hydrophobic face of the predicted alpha-helix and also by biotinylation of conserved lysines (which line the interfacial region). Circular dichroism spectroscopy reveals a general correlation between the amount of lipid-induced alpha-helix content and the degree of binding to PS-containing vesicles. Two point mutations associated with Parkinson's disease have little (A30P) or no (A53T) effect on lipid binding or alpha-helicity. These results are consistent with the hypothesis that alpha-synuclein's normal functions depend on an ability to undergo a large conformational change in the presence of specific phospholipids.
Perrin
R J
RJ
Department of Molecular and Integrative Physiology, University of Illinois, Urbana, Illinois 61801, USA.
Woods
W S
WS
Clayton
D F
DF
George
J M
JM
D003001:Cloning, Molecular; D006801:Humans; D016297:Mutagenesis, Site-Directed; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010300:Parkinson Disease / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D017354:Point Mutation; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051843:Synucleins; D051844:alpha-Synuclein
D009419:Nerve Tissue Proteins; D010743:Phospholipids; D011993:Recombinant Fusion Proteins; C497604:SNCA protein, human; D051843:Synucleins; D051844:alpha-Synuclein