Effects of metal ions on aggregation of Parkinson’sdiseaseprotein,α-synuclein
Typ
Examensarbete för masterexamen
Program
Biotechnology (MPBIO), MSc
Publicerad
2019
Författare
Lorentzon, Emma
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Parkinson’s disease (PD) is one of the most common neurodegenerative diseases worldwide. The pathology of the disease is characterized by the loss of dopaminergic neurons in the motor center of the brain, substantia nigra, coupled with amyloid aggregates of α-synuclein(α-syn) in the cytoplasm known as Lewy bodies. The brain has tight control of metal ions homeostasis but is known to accumulate metal over time. Researches have previously noted the increase of metal ions in PD patients brains, and a high concentration of iron has been found in Lewy bodies. Evidence suggests that disrupted metal homeostasis may play an important role in the development of neurodegenerative diseases, by causing oxidative stress and abnormal interactions with proteins. α-syn has been shown to be a metal binding protein, and its interactions with metals may play a role in the aggregation kinetics. α-syn can exist in many forms; C-terminally truncated, with disease-promoting mutations (e.g. A53T), and it was recently shown to be N-terminal acetylated in vivo. These versions are important to study to gain a better understanding of metal-interactions and their role in aggregation. In this thesis, I studied α-syn aggregation in the presence of the biochemically active metals copper (Cu(II)), iron (Fe(III)), manganese (Mn(II)) and zinc (Zn(II)). This was done using ThT-fluorescence aggregation assays to compare aggregation kinetics, circular dichroism (CD) to study the tertiary structure and metal binding, and imaging of the fibrils with atomic force microscopy (AFM) and transmission electron microscopy (TEM).
The results in this thesis show the importance of Fe(III) in the aggregation kinetics for α-syn wild-type (WT), A53T and acetylated α-syn. Cu(II) had less impact on the aggregation of acetylated protein; in accord with the N-terminus being important in Cu-binding. This also suggests a less important role of Cu(II) in α-syn aggregation in vivo. Truncated α-syn aggregation kinetics was not affected by the metal ions, suggesting that metal binding occurs in the missing C-terminal, or its aggregation was too fast to be affected by metals binding. Mn(II) and Zn(II) did not affect any α-syn versions’ aggregation; indicating weak or no binding of the metal ions, and thus no direct effect on aggregation.
Beskrivning
Ämne/nyckelord
alpha synuclein, aggregation kinetics, Parkinson’s disease, metal interaction, copper, iron, zinc, manganese