alpha-Synuclein expression levels do not significantly affect proteasome function and expression in mice and stably transfected PC12 cell lines.
alpha-Synuclein (alpha-syn) is a small protein of unknown function that is found aggregated in Lewy bodies, the histopathological hallmark of sporadic Parkinson disease and other synucleinopathies. Mutations in the alpha-syn gene and a triplication of its gene locus have been identified in early onset familial Parkinson disease. alpha-Syn turnover can be mediated by the proteasome pathway. A survey of published data may lead to the suggestion that overexpression of alpha-syn wild type, and/or their variants (A53T and A30P), may produce a decrease in proteasome activity and function, contributing to alpha-syn aggregation. To investigate the relationship between synuclein expression and proteasome function we have studied proteasome peptidase activities and proteasome subunit expression (alpha, beta-constitutive, and inducible) in mice either lacking alpha-syn (knock-out mice) or transgenic for human alpha-syn A30P (under control of PrP promoter, at a time when no clear gliosis can be observed). Similar studies are presented in PC12 cells overexpressing enhanced yellow fluorescent protein fusion constructs of human wild type, A30P, and A53T alpha-syn. In these cell lines we have also analyzed the assembly of 20 S proteasome complex and the degradation rate of a well known substrate of the proteasome pathway, Ikappabalpha. Overall the data obtained led us to the conclusion that alpha-synuclein expression levels by themselves have no significant effect on proteasome peptidase activity, subunit expression, and proteasome complex assembly and function. These results strengthen the suggestion that other mechanisms resulting in synuclein aggregation (not simply expression levels) may be the key to understand the possible effect of aggregated synuclein on proteasome function.
Departamento de Bioquìmica e Instituto de Investigaciones Biomédicas Alberto Sols, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Cientìfica, Facultad de Medicina UAM, 28029 Madrid, Spain.
Begoña
B
Martìn-Clemente
Beatriz
B
Alvarez-Castelao
Isabel
I
Mayo
Ana Belén
AB
Sierra
Virginia
V
Dìaz
Miguel
M
Milán
Isabel
I
Fariñas
Teresa
T
Gómez-Isla
Isidro
I
Ferrer
José G
JG
Castaño
D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D004195:Disease Models, Animal; D014644:Genetic Variation; D015151:Immunoblotting; D047468:Immunoprecipitation; D008164:Luminescent Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009097:Multienzyme Complexes / Q000737:chemistry; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000096:biosynthesis*; D016716:PC12 Cells; D010300:Parkinson Disease; D010957:Plasmids / Q000378:metabolism; D011328:Prions / Q000235:genetics; D011401:Promoter Regions, Genetic; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D051843:Synucleins; D013997:Time Factors; D014162:Transfection; D019076:Transgenes; D051844:alpha-Synuclein
D001426:Bacterial Proteins; D008164:Luminescent Proteins; D009097:Multienzyme Complexes; D009419:Nerve Tissue Proteins; D011328:Prions; C497605:Snca protein, mouse; C497606:Snca protein, rat; D051843:Synucleins; D051844:alpha-Synuclein; C054562:yellow fluorescent protein, Bacteria; D046988:Proteasome Endopeptidase Complex