Functional consequences of alpha-synuclein tyrosine nitration: diminished binding to lipid vesicles and increased fibril formation.
Previous studies have shown the presence of nitrated alpha-synuclein (alpha-syn) in human Lewy bodies and other alpha-syn inclusions. Herein, the effects of tyrosine nitration on alpha-syn fibril formation, lipid binding, chaperone-like function, and proteolytic degradation were systematically examined by employing chromatographically isolated nitrated monomeric, dimeric, and oligomeric alpha-syn. Nitrated alpha-syn monomers and dimers but not oligomers accelerated the rate of fibril formation of unmodified alpha-syn when present at low concentrations. Immunoelectron microscopy revealed that nitrated monomers and dimers are incorporated into the fibrils. However, the purified nitrated alpha-syn monomer by itself was unable to form fibrils. Nitration of the tyrosine residue at position 39 was largely responsible for decreased binding of nitrated monomeric alpha-syn to synthetic vesicles, which correlated with an impairment of the nitrated protein to adopt alpha-helical conformation in the presence of liposomes. The chaperone-like activity of alpha-syn was not inhibited by nitration or oxidation. Furthermore, the 20 S proteasome and calpain I degraded nitrated monomeric alpha-syn, although at a slower rate compared with control alpha-syn. Collectively, these data suggest that post-translational modification of alpha-syn by nitration can promote the formation of intracytoplasmic inclusions that constitute the hallmark of Parkinson disease and other synucleinopathies.
Hodara
Roberto
R
Stokes Research Institute and Department of Biochemistry and Biophysics, Children's Hospital of Philadelphia and the University of Pennsylvania, 19104, USA.
Norris
Erin H
EH
Giasson
Benoit I
BI
Mishizen-Eberz
Amanda J
AJ
Lynch
David R
DR
Lee
Virginia M-Y
VM
Ischiropoulos
Harry
H
D000818:Animals; D002154:Calpain / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000737:chemistry / Q000378:metabolism; D050356:Lipid Metabolism; D051379:Mice; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D009566:Nitrates / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D020836:Protein Structure, Quaternary; D051843:Synucleins; D014443:Tyrosine / Q000378:metabolism*; D051844:alpha-Synuclein
D007328:Insulin; D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins; D009566:Nitrates; C497604:SNCA protein, human; C497605:Snca protein, mouse; D051843:Synucleins; D051844:alpha-Synuclein; D014443:Tyrosine; D002154:Calpain; D046988:Proteasome Endopeptidase Complex; D010100:Oxygen