TY - JOUR
T1 - Accelerated formation of α-synuclein oligomers by concerted action of the 20s proteasome and familial parkinson mutations
AU - Lewis, Karen A.
AU - Yaeger, Arynn
AU - Demartino, George N.
AU - Thomas, Philip J.
N1 - Funding Information:
Acknowledgements We thank Rakez Kayed (University of Texas Medical Branch at Galveston, TX) for allowing K.A.L. to perform initial anti-oligomer experiments his laboratory, the kind gift of the I-11 antibody, helpful discussion and execution of critical experiments, and critical review of the manuscript. Thanks to Chang-wei Liu (University of Colorado Health Sciences Center, Denver, CO) for helpful discussions and critical reading of the manuscript. We acknowledge the Protein Technology Core Facility at UT-Southwestern for mass spectrometry. This work was supported by grants from the National Institutes of Health (NIH) to P.J.T. [DK49835] and G.N.D. [DK46181], the Parkinson’s Disease Foundation to P.J.T., and an NIH training grant to K.A.L. [GM07062].
PY - 2010/2
Y1 - 2010/2
N2 - A hallmark of Parkinson disease (PD) is the formation of intracellular protein inclusions called Lewy bodies that also contain mitochondria. α-Synuclein (αSyn) is a major protein component of Lewy bodies, where it is in an amyloid conformation and a significant fraction is truncated by poorly understood proteolytic events. Previously, we demonstrated that the 20S proteasome cleaves αSyn in vitro to produce fragments like those observed in Lewy bodies and that the fragments accelerate the formation of amyloid fibrils from full-length αSyn. Three point mutations in αSyn are associated with early-onset familial PD: A30P, E46K, and A53T. However, these mutations have very different effects on the amyloidogenicity and vesicle-binding activity of αSyn, suggesting neither of these processes directly correlate with neurodegeneration. Here, we evaluate the effect of the disease-associated mutations on the fragmentation, conformation, and association reactions of αSyn in the presence of the 20S proteasome and liposomes. The 20S proteasome produced the C-terminal fragments from both the mutant and wildtype αSyn. These truncations accelerated fibrillization of all α-synucleins, but again there was no clear correlation between the PD-associated mutations and amyloid formation in the presence of liposomes. Recent data suggests that cellular toxicity is caused by a soluble oligomeric species, which is a precursor to the amyloid form and is immunologically distinguishable from both soluble monomeric and amyloid forms of αSyn. Notably, the rate of formation of the soluble, presumptively cytotoxic oligomers correlated with the disease-associated mutations when both 20S proteasome and liposomes were present. Under these conditions, the wildtype protein was also cleaved and formed the oligomeric structures, albeit at a slower rate, suggesting that 20S-mediated truncation of αSyn may play a role in sporadic PD as well. Evaluation of the biochemical reactions of the PD-associated α-synuclein mutants in our in vitro system provides insight into the possible pathogenetic mechanism of both familial and sporadic PD.
AB - A hallmark of Parkinson disease (PD) is the formation of intracellular protein inclusions called Lewy bodies that also contain mitochondria. α-Synuclein (αSyn) is a major protein component of Lewy bodies, where it is in an amyloid conformation and a significant fraction is truncated by poorly understood proteolytic events. Previously, we demonstrated that the 20S proteasome cleaves αSyn in vitro to produce fragments like those observed in Lewy bodies and that the fragments accelerate the formation of amyloid fibrils from full-length αSyn. Three point mutations in αSyn are associated with early-onset familial PD: A30P, E46K, and A53T. However, these mutations have very different effects on the amyloidogenicity and vesicle-binding activity of αSyn, suggesting neither of these processes directly correlate with neurodegeneration. Here, we evaluate the effect of the disease-associated mutations on the fragmentation, conformation, and association reactions of αSyn in the presence of the 20S proteasome and liposomes. The 20S proteasome produced the C-terminal fragments from both the mutant and wildtype αSyn. These truncations accelerated fibrillization of all α-synucleins, but again there was no clear correlation between the PD-associated mutations and amyloid formation in the presence of liposomes. Recent data suggests that cellular toxicity is caused by a soluble oligomeric species, which is a precursor to the amyloid form and is immunologically distinguishable from both soluble monomeric and amyloid forms of αSyn. Notably, the rate of formation of the soluble, presumptively cytotoxic oligomers correlated with the disease-associated mutations when both 20S proteasome and liposomes were present. Under these conditions, the wildtype protein was also cleaved and formed the oligomeric structures, albeit at a slower rate, suggesting that 20S-mediated truncation of αSyn may play a role in sporadic PD as well. Evaluation of the biochemical reactions of the PD-associated α-synuclein mutants in our in vitro system provides insight into the possible pathogenetic mechanism of both familial and sporadic PD.
KW - 20S proteasome
KW - Amyloid
KW - Cytotoxicity
KW - Endoproteolysis
KW - Liposomes
KW - Parkinson disease
KW - Soluble oligomers
KW - αSynuclein
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UR - http://www.scopus.com/inward/citedby.url?scp=77950021983&partnerID=8YFLogxK
U2 - 10.1007/s10863-009-9258-y
DO - 10.1007/s10863-009-9258-y
M3 - Article
C2 - 20148295
AN - SCOPUS:77950021983
SN - 0145-479X
VL - 42
SP - 85
EP - 95
JO - Journal of Bioenergetics and Biomembranes
JF - Journal of Bioenergetics and Biomembranes
IS - 1
ER -