CONSTRUCTION OF MODEL STRAIN OF YEAST SACCHAROMYCES CEREVISIAE WITH REGULATED EXPRESSION OF RECOMBINANT HUMAN ALPHA-SYNUCLEIN

Abstract

Background. Improper folding and accumulation of a-synuclein aggregates are among the causes of Parkinson’s disease. The most important factor influencing the process of α-synuclein aggregation is the level of this protein in neurons which depends on the balance between its synthesis, degradation and secretion. Under certain conditions, when α-synuclein is synthesized at a high level, monomers of this protein can aggregate on the lipid membrane, which leads to the formation of amyloids, fibrils and protofibrils unable to perform their physiological functions. Since it is virtually impossible to study the properties of α-synuclein in vivo, researchers are actively using model biological systems (single-celled microorganisms, human cell lines, animal models etc.).
The aim of this study was to construct a recombinant strain of Saccharomyces cerevisiae with controlled expression of human α-synuclein to study the regulation and properties of this protein and for screening for new low molecular weight chemi­cal compounds which can induce α-synuclein aggregation and/or degradation.
Materials and methods. A recombinant strain of S. cerevisiae with controlled expression of α-synuclein conjugated to a green fluorescent protein was isolated. Western blotting with specific anti-α-synuclein antibodies was used to detect recombinant α-synuclein in yeast cells. Intracellular localization of heterologous chimeric green fluorescent protein conjugated to α-synuclein was also examined by fluorescence microscopy.
Results. To construct a recombinant strain of S. cerevisiae, the coding sequence of the human wild-type α-synuclein gene was expressed under the regulated promoter of the ScMET25 gene. Analysis of the effect of different concentrations of exogenous methionine as a factor regulating the expression of the ScMET25 promoter on the content of recombinant protein showed that the expression of the human α-synuclein gene in S. cerevisiae is repressed in the presence of methionine at a concentration of 10 mg/L and higher. During long-term cultivation of yeast cells, this effect decreased due to the depletion of methionine in the growth medium. As a result, recombinant protein synthesis was restored, and α-synuclein content in such cells approached that of cells grown in a medium with a low concentration of (5 mg/L), or without methionine. It was also found that overproduction of recombinant α-synuclein in S. cerevisiae cells had virtually no effect on culture growth, indicating the absence or a very weak toxic effect of human α-synuclein on yeast physiology.
Conclusions. The obtained data indicate a concentration-dependent effect of methionine on the level of recombinant α-synuclein synthesis in S. cerevisiae yeast cells. Such controlled expression of the studied protein can be used to screen for compounds capable of promoting dose-dependent aggregation or degradation of α-synuclein in yeast cells and potentially in human cells as well.