Cleavage of alpha-synuclein by calpain: potential role in degradation of fibrillized and nitrated species of alpha-synuclein.
Alpha-synuclein (alpha-syn) is a major protein component of the neuropathological hallmarks of Parkinson's disease and related neurodegenerative disorders termed synucleinopathies. Neither the mechanism of alpha-syn fibrillization nor the degradative process for alpha-syn has been elucidated. Previously, we showed that wild-type, mutated, and fibrillar alpha-syn proteins are substrates of calpain I in vitro. In this study, we demonstrate that calpain-mediated cleavage near and within the middle region of soluble alpha-syn with/without tyrosine nitration and oxidation generates fragments that are unable to self-fibrillize. More importantly, these fragments prevent full-length alpha-syn from fibrillizing. Calpain-mediated cleavage of alpha-syn fibrils composed of wild-type or nitrated alpha-syn generate C-terminally truncated fragments that retain their fibrillar structure and induce soluble full-length alpha-syn to co-assemble. Therefore, calpain-cleaved soluble alpha-syn inhibits fibrillization, whereas calpain-cleaved fibrillar alpha-syn promotes further co-assembly. These results provide insight into possible disease mechanisms underlying synucleinopathies since the formation of alpha-syn fibrils could be causally linked to the onset/progression of these disorders.
Mishizen-Eberz
Amanda J
AJ
Department of Neurology, University of Pennsylvania and The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA.
Norris
Erin H
EH
Giasson
Benoit I
BI
Hodara
Roberto
R
Ischiropoulos
Harry
H
Lee
Virginia M-Y
VM
Trojanowski
John Q
JQ
Lynch
David R
DR
D002154:Calpain / Q000737:chemistry* / Q000378:metabolism; D002918:Chymotrypsin / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D016253:Microscopy, Immunoelectron; D009410:Nerve Degeneration / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D009566:Nitrates / Q000737:chemistry / Q000378:metabolism*; D010300:Parkinson Disease / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D010446:Peptide Fragments / Q000378:metabolism; D030421:Peroxynitrous Acid / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012995:Solubility; D051843:Synucleins; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism; D051844:alpha-Synuclein
D009419:Nerve Tissue Proteins; D009566:Nitrates; D010446:Peptide Fragments; D011994:Recombinant Proteins; C497604:SNCA protein, human; D051843:Synucleins; D051844:alpha-Synuclein; D030421:Peroxynitrous Acid; C002744:3-nitrotyrosine; D014443:Tyrosine; D002918:Chymotrypsin; D002154:Calpain