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Characterization of the interaction of synemin-L & nestin with desmin, a major structural protein in muscles

Zugschwerdt, Petra

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Abstract

In desminopathies, protein aggregates of desmin (des) are found together with other proteins from the intermediate filament (IF) protein family such as nestin (nes) and synemin (syn) within the muscle of patients. It is not known if or what role des associated proteins play within the aggregation process of mutant des. We have systematically characterized the biochemical properties of both human syn-L and tail truncated nes as well as their interaction with des and vimentin (vim). After renaturation into buffers of low ionic strength, syn was determined to be a monomer, and it only formed oligomeric structures of distinct size under IF assembly conditions. A major topic of this thesis was to characterize its in vitro interaction with des and vim. Surprisingly, syn exhibited a strong negative impact on the filament forming process of des and vim, both when proteins were mixed before or after renaturation. The addition of syn to pre-assembled filaments caused the formation of globular protein structures within the filament network and at its ends. Employing domain- truncated variants of des and vim for assembly experiments of syn, we determined the rod domain of des and vim as binding site for syn. The study of the tail-truncated variant of nes revealed a significant pH-sensitive solubility. Aggregates formed by nes under assembly conditions seemed to be unordered. Nes interacted with des during renaturation but not afterwards. “Unit length filament”-like structures formed by mutant vimY117L and desY122L were covered by a proteinacous mass assembled in the presence of nes. No filaments but huge protein aggregates were visualized when nes was renaturated and co-assembled with des under assembly conditions, but addition of nes after renaturation of des caused the occasional decoration of seemingly intact des IFs with irregular protein structures. Addition of nes before or after renaturation of vim altered the size of protein aggregates found besides intact filaments. Our in vitro-data suggest that syn and nes are no bona fide IF proteins but IF-associated proteins. Because nes is only coating filaments and syn aggressively integrates into pre-existing IFs, and because both are not able to form IFs, the role of syn and nes as structural components in both normal and diseased muscle should be analysed now from a completely different point of view.

Item Type: Dissertation
Supervisor: Herrmann-Lerdon, Prof. Dr. Harald
Date of thesis defense: 11 May 2015
Date Deposited: 16 Oct 2015 05:23
Date: 2015
Faculties / Institutes: The Faculty of Bio Sciences > Dean's Office of the Faculty of Bio Sciences
Service facilities > German Cancer Research Center (DKFZ)
Subjects: 570 Life sciences
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