Accelerated proteasomal activity induced by Pb2+, Ga 3+, or Cu2+ exposure does not induce degradation of αt-Synuclein

Nurit Grunberg-Etkovitz, Nirit Lev, Debby Ickowicz, Almog Avital, Daniel Offen, Zvi Malik

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7 Scopus citations


The involvement of environmental heavy metals in Parkinson's disease (PD) has been suggested by epidemiologic studies; however, the mechanism of this effect is unknown. PD is characterized by the aggregation of α-synuclein in Lewy bodies. We previously showed that Pb2+ accelerates proteasomal activity. Therefore, we examined the effect of Pb2+, Ga3+, and Cu2+ on α-synuclein in human SH-SY5Y cells. The heavy metals induced an increase in heme-oxygenase-1 levels without significant cell death or ROS generation. The metals inhibited ALA-dehydratase, which is the inhibitory subunit of the proteasome, thereby accelerating proteasomal activity and decreasing protein levels of CDK-1 and PBGD. However, α-synuclein protein levels increased after exposure to metals, similar to the effect obtained with the proteasome inhibitor, hemin, suggesting that α-synuclein is inaccessible to proteasomal degradation. Indeed, electron microscopy revealed the formation of aggresomes in Pb2+- or hemin-treated cells. Thus, although heavy metals enhance proteasomal activity, α-synuclein is protected from degradation, and its protein levels and aggregation are increased.

Original languageEnglish
Pages (from-to)5-24
Number of pages20
JournalJournal of Environmental Pathology, Toxicology and Oncology
Issue number1
StatePublished - 2009


  • A53T mutant
  • Heavy metals
  • Heme-oxygenase-1


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