Calcium-triggered membrane interaction of the alpha-synuclein acidic tail.
Alpha-synuclein (alpha-syn) is a 140-residue protein that aggregates in intraneuronal inclusions called Lewy bodies in Parkinson's disease (PD). It is composed of an N-terminal domain with a propensity to bind lipids and a C-terminal domain rich in acidic residues (the acidic tail). The objective of this study was to examine the effect of Ca(2+) on the acidic tail conformation in lipid-bound alpha-syn. We exploit the extreme sensitivity of the band III fluorescence emission peak of the pyrene fluorophore to the polarity of its microenvironment to monitor subtle conformational response of the alpha-syn acidic tail to Ca(2+). Using recombinant human alpha-syn bearing a pyrene to probe either the N-terminal domain or the acidic tail, we noted that lipid binding resulted in an increase in band III emission intensity in the pyrene probe tagging the N-terminal domain but not that in the acidic tail. This suggests that the protein is anchored to the lipid surface via the N-terminal domain. However, addition of Ca(2+) caused an increase in band III emission intensity in the pyrene tagging the acidic tail, with a corresponding increased susceptibility to quenching by quenchers located in the lipid milieu, indicative of lipid interaction of this domain. Taken together with the increased beta-sheet content of membrane-associated alpha-syn in the presence of Ca(2+), we propose a model wherein initial lipid interaction occurs via the N-terminal domain, followed by a Ca(2+)-triggered membrane association of the acidic tail as a potential mechanism leading to alpha-syn aggregation. These observations have direct implications in the role of age-related oxidative stress and the attendant cellular Ca(2+) dysregulation as critical factors in alpha-syn aggregation in PD.
Tamamizu-Kato
Shiori
S
Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr. Way, Oakland, California 94609, USA.
Kosaraju
Malathi G
MG
Kato
Hiroyuki
H
Raussens
Vincent
V
Ruysschaert
Jean-Marie
JM
Narayanaswami
Vasanthy
V
D000241:Adenosine / Q000031:analogs & derivatives / Q000737:chemistry; D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002942:Circular Dichroism; D005453:Fluorescence; D020404:Glycerophospholipids / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D010713:Phosphatidylcholines / Q000737:chemistry; D011487:Protein Conformation; D011721:Pyrenes / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051844:alpha-Synuclein / Q000737:chemistry* / Q000378:metabolism*
C509561:1-palmitoyl-2-oleoyl-phosphatidyl-3-adenosine; D020404:Glycerophospholipids; D008051:Lipid Bilayers; D008563:Membrane Lipids; D010713:Phosphatidylcholines; D011721:Pyrenes; D011994:Recombinant Proteins; D051844:alpha-Synuclein; D000241:Adenosine; D002118:Calcium; C028694:1-palmitoyl-2-oleoylphosphatidylcholine