Ubiquitination of alpha-synuclein

Area of Science:

• Neuroscience
• Biochemistry
• Molecular Biology

Background:

• Filamentous alpha-synuclein aggregates characterize neurodegenerative diseases like Parkinson's disease (PD).
• Alpha-synuclein is known to be phosphorylated at Ser129 and ubiquitinated in affected brains.
• Understanding ubiquitination patterns is crucial for elucidating disease mechanisms.

Purpose of the Study:

• To investigate the ubiquitination sites of alpha-synuclein in vitro and in vivo.
• To determine the impact of familial PD-linked mutations, phosphorylation, and fibril formation on alpha-synuclein ubiquitination.

Main Methods:

• Protein-sequence analysis and site-directed mutagenesis to identify in vitro ubiquitination sites.
• In vitro studies examining the effects of Ser129 phosphorylation and fibril formation on ubiquitination.
• In vivo ubiquitination analysis in 293T cells via co-transfection with alpha-synuclein and ubiquitin.

Main Results:

• In vitro, Lys21, Lys23, Lys32, and Lys34 were identified as major ubiquitination sites.
• Assembled, filamentous alpha-synuclein showed reduced ubiquitination compared to soluble forms, with major sites at Lys6, Lys10, and Lys12.
• Familial PD-linked mutations (A53T, A30P) and Ser129 phosphorylation did not significantly alter ubiquitination in vitro or in vivo.

Conclusions:

• Ubiquitination of alpha-synuclein occurs at distinct sites depending on its soluble or filamentous state.
• In vivo ubiquitination sites in filamentous alpha-synuclein mirror those identified in vitro.
• These findings offer insights into the formation of alpha-synuclein deposits in alpha-synucleinopathies.