Ubiquitylation of synphilin-1 and alpha-synuclein by SIAH and its presence in cellular inclusions and Lewy bodies imply a role in Parkinson's disease.
Parkinson's disease (PD) is a neurodegenerative disease characterized by Lewy body formation and death of dopaminergic neurons. Mutations in alpha-synuclein and parkin cause familial forms of PD. Synphilin-1 was shown to interact with alpha-synuclein and to promote the formation of cytosolic inclusions. We now report that synphilin-1 interacts with the ... E3 ubiquitin-ligases SIAH-1 and SIAH-2. SIAH proteins ubiquitylate synphilin-1 both in vitro and in vivo, promoting its degradation by the ubiquitin-proteasome system. Inability of the proteasome to degrade synphilin-1/SIAH complex leads to a robust formation of ubiquitylated cytosolic inclusions. Ubiquitylation is required for inclusion formation, because a catalytically inactive mutant of SIAH-1, which still binds to synphilin-1, fails to promote inclusions. Like synphilin-1, alpha-synuclein associates with SIAH in intact cells, but the interaction with SIAH-2 was much stronger that with SIAH-1. In vitro experiments show that SIAH-2 monoubiquitylates alpha-synuclein. Further evidence that SIAH proteins may play a role in inclusion formation comes from the demonstration of SIAH immunoreactivity in Lewy bodies of PD patients.
Mesh Terms:
Animals, Brain, Carrier Proteins, Cell Line, Humans, Inclusion Bodies, Lewy Bodies, Nerve Tissue Proteins, Nuclear Proteins, Parkinson Disease, Protein Binding, Proteins, Rats, Recombinant Fusion Proteins, Synucleins, Transcription Factors, Transfection, Ubiquitin, Ubiquitin-Protein Ligases, alpha-Synuclein
Animals, Brain, Carrier Proteins, Cell Line, Humans, Inclusion Bodies, Lewy Bodies, Nerve Tissue Proteins, Nuclear Proteins, Parkinson Disease, Protein Binding, Proteins, Rats, Recombinant Fusion Proteins, Synucleins, Transcription Factors, Transfection, Ubiquitin, Ubiquitin-Protein Ligases, alpha-Synuclein
Proc. Natl. Acad. Sci. U.S.A.
Date: Apr. 13, 2004
PubMed ID: 15064394
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