Distinct cleavage patterns of normal and pathologic forms of alpha-synuclein by calpain I in vitro.
Parkinson's disease (PD) is characterized by fibrillary neuronal inclusions called Lewy bodies (LBs) consisting largely of alpha-synuclein (alpha-syn), the protein mutated in some patients with familial PD. The mechanisms of alpha-syn fibrillization and LB formation are unknown, but may involve aberrant degradation or turnover. We examined the ability of calpain I to cleave alpha-syn in vitro. Calpain I cleaved wild-type alpha-syn predominantly after amino acid 57 and within the non-amyloid component (NAC) region. In contrast, calpain I cleaved fibrillized alpha-syn primarily in the region of amino acid 120 to generate fragments like those that increase susceptibility to dopamine toxicity and oxidative stress. Further, while calpain I cleaved wild-type alpha-syn after amino acid 57, this did not occur in mutant A53T alpha-syn. This paucity of proteolysis could increase the stability of A53T alpha-syn, suggesting that calpain I might protect cells from forming LBs by specific cleavages of soluble wild-type alpha-syn. However, once alpha-syn has polymerized into fibrils, calpain I may contribute to toxicity of these forms of alpha-syn by cleaving at aberrant sites within the C-terminal region. Elucidating the role of calpain I in the proteolytic processing of alpha-syn in normal and diseased brains may clarify mechanisms of neurodegenerative alpha-synucleinopathies.
Mishizen-Eberz
Amanda J
AJ
Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Guttmann
Rodney P
RP
Giasson
Benoit I
BI
Day
George A
GA
Hodara
Roberto
R
Ischiropoulos
Harry
H
Lee
Virginia M-Y
VM
Trojanowski
John Q
JQ
Lynch
David R
DR
D019943:Amino Acid Substitution; D000818:Animals; D002154:Calpain / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D013058:Mass Spectrometry; D051379:Mice; D008822:Mice, Transgenic; D008970:Molecular Weight; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010300:Parkinson Disease / Q000235:genetics / Q000378:metabolism; D010446:Peptide Fragments / Q000032:analysis; D010449:Peptide Mapping; D011994:Recombinant Proteins / Q000737:chemistry; D013379:Substrate Specificity; D051843:Synucleins; D051844:alpha-Synuclein
D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; C497604:SNCA protein, human; C497605:Snca protein, mouse; D051843:Synucleins; D051844:alpha-Synuclein; D002154:Calpain