The G4C2 expansion mutation in the c9orf72 gene affects the development of neurodegenerative diseases such as ALS and FTD by several known mechanisms. One of them is the acquisition of toxic functions due to sense and antisense RNA transcripts. In the case of binding of the antisense RNA transcript to the protein phenylalanine tRNA- synthetase, inhibition of aminoacylation of tRNAPhe occurs, which has a negative impact on the course of the disease. To investigate the mode of binding and interaction, we have expressed and isolated protein using a bacterial expression system. The expression process was optimized to obtain as much protein as possible in the soluble fraction. For that purpose, we used maltose binding protein. Both subunits of the FARS protein were best expressed at 18 ⁰C with added fusion partner maltose binding protein. Proteins were isolated by nickel affinity chromatography using hexahistidine tags on both recombinant proteins. Future studies of expression and isolation should be performed on a larger scale. The isolation procedure would also have to be optimized since a lot of proteolytic degradation was detected in the present work. A better understanding of the mechanism could contribute to the development of new treatments for c9orf72-related diseases.
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