DJ-1 modulates alpha-synuclein aggregation state in a cellular model of oxidative stress: relevance for Parkinson's disease and involvement of HSP70.
BACKGROUND
Parkinson's disease (PD) is a neurodegenerative pathology whose molecular etiopathogenesis is not known. Novel contributions have come from familial forms of PD caused by alterations in genes with apparently unrelated physiological functions. The gene coding for alpha-synuclein (alpha-syn) (PARK1) has been investigated as alpha-syn is located in Lewy bodies (LB), intraneuronal inclusions in the substantia nigra (SN) of PD patients. A-syn has neuroprotective chaperone-like and antioxidant functions and is involved in dopamine storage and release. DJ-1 (PARK7), another family-PD-linked gene causing an autosomal recessive form of the pathology, shows antioxidant and chaperone-like activities too.


RESULTS
The present study addressed the question whether alpha-syn and DJ-1 interact functionally, with a view to finding some mechanism linking DJ-1 inactivation and alpha-syn aggregation and toxicity. We developed an in vitro model of alpha-syn toxicity in the human neuroblastoma cell line SK-N-BE, influencing DJ-1 and alpha-syn intracellular concentrations by exogenous addition of the fusion proteins TAT-alpha-syn and TAT-DJ-1; DJ-1 was inactivated by the siRNA method. On a micromolar scale TAT-alpha-syn aggregated and triggered neurotoxicity, while on the nanomolar scale it was neuroprotective against oxidative stress (induced by H(2)O(2) or 6-hydroxydopamine). TAT-DJ-1 increased the expression of HSP70, while DJ-1 silencing made SK-N-BE cells more susceptible to oxidative challenge, rendering TAT-alpha-syn neurotoxic at nanomolar scale, with the appearance of TAT-alpha-syn aggregates.


CONCLUSIONS
DJ-1 inactivation may thus promote alpha-syn aggregation and the related toxicity, and in this model HSP70 is involved in the antioxidant response and in the regulation of alpha-syn fibril formation.
Batelli
Sara
S
Department of Neuroscience, Mario Negri Institute for Pharmacological Research, Milan, Italy.
Albani
Diego
D
Rametta
Raffaela
R
Polito
Letizia
L
Prato
Francesca
F
Pesaresi
Marzia
M
Negro
Alessandro
A
Forloni
Gianluigi
G
D045744:Cell Line, Tumor; D018076:DNA, Complementary / Q000378:metabolism; D015723:Gene Library; D020868:Gene Silencing; D005808:Genes, Recessive; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D016631:Lewy Bodies / Q000378:metabolism; D008954:Models, Biological; D015513:Oncogene Proteins / Q000378:metabolism*; D018384:Oxidative Stress; D010300:Parkinson Disease / Q000378:metabolism*; D000071617:Protein Deglycase DJ-1; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D013378:Substantia Nigra / Q000378:metabolism; D051844:alpha-Synuclein / Q000378:metabolism / Q000502:physiology*
D018076:DNA, Complementary; D018840:HSP70 Heat-Shock Proteins; D047908:Intracellular Signaling Peptides and Proteins; D015513:Oncogene Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C000591376:Tat-DJ-1 fusion protein, human; D051844:alpha-Synuclein; C105131:PARK7 protein, human; D000071617:Protein Deglycase DJ-1