Aggresomes formed by alpha-synuclein and synphilin-1 are cytoprotective.
Lewy bodies (LBs), which are the hallmark pathologic features of Parkinson's disease and of dementia with LBs, have several morphologic and molecular similarities to aggresomes. Whether such cytoplasmic inclusions contribute to neuronal death or protect cells from the toxic effects of misfolded proteins remains controversial. In this report, the role of aggresomes in cell viability was addressed in the context of over-expressing alpha-synuclein and its interacting partner synphilin-1 using engineered 293T cells. Inhibition of proteasome activity elicited the formation of juxtanuclear aggregates with characteristics of aggresomes including immunoreactivity for vimentin, gamma-tubulin, ubiquitin, proteasome subunit, and hsp70. As expected from the properties of aggresomes, the microtubule disrupting agents, vinblastin and nocodazole, markedly prevented the formation of these inclusions. Similar to LBs, the phosphorylated form of alpha-synuclein co-localized in these synphilin-1-containing aggresomes. Although the caspase inhibitor z-VAD-fmk significantly reduced the number of apoptotic cells, it had no impact on the percentage of aggresome-positive cells. Finally, quantitative analysis revealed aggresomes in 60% of nonapoptotic cells but only in 10% of apoptotic cells. Additionally, alpha-synuclein-induced apoptosis was not coupled with increased prevalence of aggresome-bearing cells. Taken together, these observations indicate a disconnection between aggresome formation and apoptosis, and support a protective role for these inclusions from the toxicity associated with the combined over-expression of alpha-synuclein and synphilin-1.
Tanaka
Mikiei
M
Genetic Pharmacology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-1406, USA.
Kim
Yong Man
YM
Lee
Gwang
G
Junn
Eunsung
E
Iwatsubo
Takeshi
T
Mouradian
M Maral
MM
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D006801:Humans; D002479:Inclusion Bodies / Q000187:drug effects / Q000378:metabolism*; D016631:Lewy Bodies / Q000378:metabolism; D020961:Lewy Body Disease / Q000378:metabolism / Q000473:pathology; D046911:Macromolecular Substances; D008870:Microtubules / Q000187:drug effects; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology; D015739:Nocodazole / Q000494:pharmacology; D010300:Parkinson Disease / Q000378:metabolism / Q000473:pathology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051843:Synucleins; D014162:Transfection; D014747:Vinblastine / Q000494:pharmacology; D051844:alpha-Synuclein
D000590:Amino Acid Chloromethyl Ketones; D002352:Carrier Proteins; D015853:Cysteine Proteinase Inhibitors; D046911:Macromolecular Substances; D009419:Nerve Tissue Proteins; D018696:Neuroprotective Agents; D011994:Recombinant Proteins; C497604:SNCA protein, human; C118958:SNCAIP protein, human; D051843:Synucleins; D051844:alpha-Synuclein; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D014747:Vinblastine; D015739:Nocodazole