Characterization of α‐synuclein aggregation and synergistic toxicity with protein tau in yeast

Abstract

A yeast model was generated to study the mechanisms and phenotypical repercussions of expression of α‐synuclein as well as the coexpression of protein tau. The data show that aggregation of α‐synuclein is a nucleation–elongation process initiated at the plasma membrane. Aggregation is consistently enhanced by dimethyl sulfoxide, which is known to increase the level of phospholipids and membranes in yeast cells. Aggregation of α‐synuclein was also triggered by treatment of the yeast cells with ferrous ions, which are known to increase oxidative stress. In addition, data are presented in support of the hypothesis that degradation of α‐synuclein occurs via autophagy and proteasomes and that aggregation of α‐synuclein disturbs endocytosis. Reminiscent of observations in double‐transgenic mice, coexpression of α‐synuclein and protein tau in yeast cells is synergistically toxic, as exemplified by inhibition of proliferation. Taken together, the data show that these yeast models recapitulate major aspects of α‐synuclein aggregation and cytotoxicity, and offer great potential for defining the underlying mechanisms of toxicity and synergistic actions of α‐synuclein and protein tau.

Effect of Ser-129 Phosphorylation on Interaction of α-Synuclein with Synaptic and Cellular Membranes

“…Consistent with our previous findings (30), we found that the relative amount of synaptosomal ␣-syn in the membrane-bound and cytosolic fractions was similar for WT, A30P and A53T ␣-syn. Experiments in yeast have suggested that A30P ␣-syn has a lower membrane binding capacity than WT and A53T ␣-syn (41,42). However, we have previously shown that cytosolic factors expressed in brain, which yeast may lack, influence the membrane binding ability of recombinant ␣-syn and can indeed increase the binding capacity of A30P ␣-syn (11).…”

α-Synuclein–induced Aggregation of Cytoplasmic Vesicles inSaccharomyces cerevisiae

“…As shown previously (Outeiro and Lindquist, 2003;Zabrocki et al, 2005;Dixon et al, 2005), ␣-syn-EGFP prominently localized to plasma membranes and formed cytoplasmic accumulations, whereas EGFP alone showed a diffuse cytoplasmic distribution ( Figures 1A and 2A). The ␣-syn clusters/accumulations varied considerably in size, and many of the smaller ones appeared to be associated with the cell cortex, whereas larger accumulations were sometimes completely localized to the cytoplasm, suggesting that they may form initially at the plasma membrane or the ER, which underlies the plasma membrane in yeast ( Figure 1D).…”

“…These cells produced twice the percentage of cytoplasmic ␣-syn accumulations as the nonintegrated strain (Supplementary Figure 2). The number of cells with ␣-syn accumulations was further enhanced to ϳ70% by treatment of these yeast with 5% DMSO (Zabrocki et al, 2005). Surprisingly, EM analyses of the cells expressing ␣-syn-EGFP did not reveal filamentous ␣-syn-or LB-like structures.…”

Interplay between Sumoylation and Phosphorylation for Protection against α-Synuclein Inclusions

“…Soluble ␣Syn can be targeted to the 26 S proteasome for degradation (31)(32)(33)(34) or can be degraded by the autophagy-lysosomal pathway (33)(34)(35)(36). The budding yeast Saccharomyces cerevisiae has been extensively used as a powerful system to study the basic molecular mechanisms involved in ␣Syn-mediated cytotoxicity (37)(38)(39)(40). We showed that aggregate clearance of ␣Syn depends mainly on the autophagy pathway (38).…”