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Disease-related amyloidogenic variants of human lysozyme trigger the unfolded protein response and disturb eye development in Drosophila melanogaster
University of Cambridge.
Linköping University, Department of Physics, Chemistry and Biology, Molecular Biotechnology. Linköping University, The Institute of Technology.
University of Cambridge.
University of Cambridge.
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2012 (English)In: The FASEB Journal, ISSN 0892-6638, E-ISSN 1530-6860, Vol. 26, no 1, 192-202 p.Article in journal (Refereed) Published
Abstract [en]

We have created a Drosophila model of lysozyme amyloidosis to investigate the in vivo behavior of disease-associated variants. To achieve this objective, wild-type (WT) protein and the amyloidogenic variants F57I and D67H were expressed in Drosophila melanogaster using the UAS-gal4 system and both the ubiquitous and retinal expression drivers Act5C-gal4 and gmr-gal4. The nontransgenic w(1118) Drosophila line was used as a control throughout. We utilized ELISA experiments to probe lysozyme protein levels, scanning electron microscopy for eye phenotype classification, and immunohistochemistry to detect the unfolded protein response (UPR) activation. We observed that expressing the destabilized F57I and D67H lysozymes triggers UPR activation, resulting in degradation of these variants, whereas the WT lysozyme is secreted into the fly hemolymph. Indeed, the level of WT was up to 17 times more abundant than the variant proteins. In addition, the F57I variant gave rise to a significant disruption of the eye development, and this correlated to pronounced UPR activation. These results support the concept that the onset of familial amyloid disease is linked to an inability of the UPR to degrade completely the amyloidogenic lysozymes prior to secretion, resulting in secretion of these destabilized variants, thereby leading to deposition and associated organ damage.-Kumita, J. R., Helmfors, L., Williams, J., Luheshi, L. M., Menzer, L., Dumoulin, M., Lomas, D. A., Crowther, D. C., Dobson, C. M., Brorsson, A.-C. Disease-related amyloidogenic variants of human lysozyme trigger the unfolded protein response and disturb eye development in Drosophila melanogaster.

Place, publisher, year, edition, pages
Federation of American Society of Experimental Biology (FASEB) , 2012. Vol. 26, no 1, 192-202 p.
National Category
Natural Sciences
URN: urn:nbn:se:liu:diva-73186DOI: 10.1096/fj.11-185983ISI: 000299202200020PubMedID: 21965601OAI: diva2:468482

funding agencies|Swedish Research Council||Biotechnology and Biological Sciences Research Council| BB/E019927/1 BBH0038431 |Wellcome Trust||Leverhulme Trust||European Commission| LSHM-CT-2006-037525/EURAMY |Medical Research Council| G0700990 |VINNOVA||

Available from: 2011-12-21 Created: 2011-12-21 Last updated: 2014-09-10
In thesis
1. Understanding the dual nature of lysozyme: part villain – part hero: A Drosophila melanogaster model of lysozyme amyloidosis
Open this publication in new window or tab >>Understanding the dual nature of lysozyme: part villain – part hero: A Drosophila melanogaster model of lysozyme amyloidosis
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Amyloid proteins are a distinct class of proteins that can misfold into β-sheet rich structures that later mature to form the characteristic species known as amyloid fibrils, and accumulate in tissues in the human body. The misfolding event is often caused by mutations (or outer factors such as changes in pH) that destabilize the native protein structure. The mature amyloid fibrils were initially believed to be associated with diseases connected to protein misfolding such as Alzheimer’s disease (AD), Parkinson’s disease, transthyretin amyloidosis and lysozyme amyloidosis. However, now it is known that many different factors are involved in these diseases such as failure in protein clearance, lysosomal dysfunction and formation of intermediate misfolded protein species, which possess cytotoxic properties, preceding the formation of mature fibrils.

In this thesis the amyloidogenic protein lysozyme has been examined in vivo by using Drosophila melanogaster (fruit fly) as a model organism. The effects of over-expressing human lysozyme and amyloidogenic variants in Drosophila have been investigated both in the absence and presence of the serum amyloid P component (SAP), a protein known to interact with amyloid species. In addition, the role of lysozyme in AD has been investigated by  co-expressing human lysozyme and amyloid β in Drosophila.

The lysozyme protein is an enzyme naturally found in bodily fluids such as tears, breast milk and saliva. It is engaged in the body’s defense and acts by hydrolyzing the cell wall of invading bacteria. Certain disease-associated point mutations in the gene encoding lysozyme destabilize the protein and cause it to misfold which results in systemic amyloidosis. To investigate the in vivo misfolding behavior of lysozyme we developed and established a Drosophila model of lysozyme amyloidosis. SAP is commonly found attached to amyloid deposits in the body; however, the role of SAP in amyloid diseases is unknown. To investigate the effect of SAP in lysozyme misfolding, these two proteins were co-expressed in Drosophila.

The amyloid β peptide is involved in AD, building up the plaques found in AD patient brains. These plaques trigger neuroinflammation and since lysozyme is upregulated during various inflammation conditions, a possible role of lysozyme in AD was investigated by overexpressing lysozyme in a Drosophila model of AD. Interaction between lysozyme and the amyloid β protein was also studied by biophysical measurements.

During my work with this thesis, the dual nature of lysozyme emerged; on the one hand a villain, twisted by mutations, causing the lysozyme amyloidosis disease. On the other hand a hero, delaying the toxicity and maybe the neurological damage caused by the amyloid β peptide.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 67 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1574
National Category
Natural Sciences
urn:nbn:se:liu:diva-106647 (URN)10.3384/diss.diva-106647 (DOI)978-91-7519-405-9 (print) (ISBN)
Public defence
2014-05-05, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Available from: 2014-05-16 Created: 2014-05-16 Last updated: 2014-05-19Bibliographically approved

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